BIM-based cost estimation at early stages based on historical data

Universidade do Minho Escola de Engenharia Diogo Ferronato BIM-based cost estimation at early stages based on historical data September 2020 UMinho | 2020 Diogo Ferronato BIM-based cost estimation at early stages based on historical data Co-funded by the Erasmus+ Programme of the European Union The European Master in Building Information Modelling is a joint initiative of: Universidade do Minho Escola de Engenharia Diogo Ferronato BIM-based cost estimation at early stages based on historical data. Master Dissertation European Master in Building Information Modelling Work conducted under supervision of: Hélder Manuel da Silva e Sousa Bruno Acácio Ferreira Figueiredo Nuno Miguel Mota Alves Pires (tutor in company) September, 2020 BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ iii AUTHORSHIP RIGHTS AND CONDITIONS OF USE OF THE WORK BY THIRD PARTIES This is an academic work that can be used by third parties, as long as internationally accepted rules and good practices are respected, particularly in what concerts to author rights and related matters. Therefore, the present work may be used according to the terms of the license shown below. If the user needs permission to make use if this work in conditions that are not part of the licensing mentioned below, he/she should contact the author through the RepositóriUM platform of the University of Minho. License granted to the users of this work Attribution CC BY https://creativecommons.org/licenses/by/4.0/ BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ iv ACKNOWLEDGEMENTS To my parents, Geraldo and Sueli, and my sibling Fernanda, Camila and Felipe, for supporting me during all the moments of doubt during this journey. Without your help, none of this would have been possible. Everything I conquer in my life I owe to your love and example. To my partner Cristiane, who without, this dream would never have come true. Thank you very much for all the support, from the decision to take a master's degree and enrol in the TOEFL test until the late nights closing the dissertation. We entered together on this European master's dream, and it has been the best experience of my life. Those were difficult times of pandemics, but I had you by my side always supporting me, being available in the most challenging moments and demanding when needed. Te amo muito meu amor. To my classmates at BIM A + who became great friends, carrying for the rest of my life. With special thanks to Bianca, Camilo, Giulia, Kamal, Lucas and Marina, who also did their master's dissertation in Portugal and were very important during this process. Especially during the last week. To my supervisor Prof. Helder Sousa, for his total availability and knowledge shared during this dissertation. His corrections and special considerations were extremely important. Without your guidance, this work would not be possible to be developed. To Eng. Miguel Pires, an example of a manager and a leader. His extensive knowledge and quick practical vision and applicability of technologies are formidable. I hope that all your desire and excitement with BIM and new technologies can be fully applied in the construction industry. I extend my thanks to all the employees of the Casais Group, who never measure effort to help me or provide information when necessary. To all professors and staff of the BIM A + master's program. It was the effort made by all of you over several years that made this master's degree possible—mainly thanking Prof. Miguel Azenha and Prof. Tomo Cerovšek, who was always available to solve the problems that happened along the way. To the European Union, which, through the Erasmus Mundus Joint Master Degree Programme (EMJMD) – ERASMUS+, awarded me a full scholarship for the master's degree, covering all tuition fee and providing monthly assistance. Without this financial assistance, my participation in this program would not have been possible. To all the people and friends I met around the world during this time. Each of you left a mark and a learning experience in my life. Special thanks to Hollie and Brea, the best people to spend a locked quarantine at home. You have turned the worst period into daily laughter, mountain hikes and happy pancakes. IT WASN’T ME! BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ v STATEMENT OF INTEGRITY I hereby declare having conducted this academic work with integrity. I confirm that I have not used plagiarism or any form of undue use of information or falsification of results along the process leading to its elaboration. I further declare that I have fully acknowledged the Code of Ethical Conduct of the University of Minho. Diogo Ferronato BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ vi RESUMO A metodologia BIM está revolucionando a forma de trabalho do mercado de construção, levando à desejada digitalização e automatização ao longo de todo o ciclo de vida de um projeto. Ela consiste na combinação de três campos: tecnologias, políticas e processos. Juntos, funcionam como um recurso de conhecimento compartilhado para a informação, permitindo gerenciá-la, formando uma fonte confiável de dados para a tomada de decisões e possibilitando a todos os stakeholders colaborarem em todos os processos desde a primeira etapa do projeto. Além disso, o BIM também engloba quais dados são gerenciados em termos de criação, uso, reutilização e aplicação em modelos digitais visando o desenvolvimento e aprimoramento do projeto, construção e operação de um ou vários projetos. Dentre todos os usos possíveis para a metodologia BIM, está o suporte para a gestão de custos, vinculando as informações de custos ao modelo 3D. Esse uso é comumente conhecido como 5D BIM. Gerenciamento de custos de projetos são os processos envolvidos no planejamento, estimativa, orçamento, financiamento, gerenciamento e controle de custos, buscando finalizar o projeto dentro do orçamento aprovado e desejado do cliente ou investidor. A estimativa de custo está entre os processos preliminares mais críticos em qualquer projeto de construção. Uma estimativa de custo inicial elevada pode levar a um processo desestimulante para o cliente prosseguir com o projeto. Alternativamente, uma estimativa de custo muito baixa pode levar a problemas financeiros durante o estágio subsequente. O método da área superficial é o método mais usado para estimativas preliminares de custos. No entanto, é uma previsão e não deve ser considerada como o custo final. Durante as fases iniciais do projeto, a qualidade e a quantidade de dados disponibilizados sobre o projeto são frequentemente baixas ou não definidas, levando a várias suposições. O uso de dados históricos pode preencher a lacuna deixada pela falta de informação. No entanto, a abordagem de estimativa de custo detalhada tradicional demanda uma alta carga de trabalho. Esta dissertação propõe uma estimativa de custo baseada em BIM para os estágios iniciais do projeto com base em dados de custo históricos fornecidos por projetos anteriores e seu subsequente armazenamento em um banco de dados de custos. Por meio de pesquisas em artigos acadêmicos, dissertação de mestrado, teses de PhD, livros e diretrizes de custos e BIM, foram identificados desafios para o gerenciamento de custos durante os estágios iniciais do ciclo de vida do projeto. Entre os objetivos estavam a estimativa de custo facilmente atualizada de acordo com as mudanças de layout e possibilitar a atualização da estimativa de custo conforme o modelo BIM evolui. Para tanto, foi desenvolvido um workflow utilizando uma adaptação do método de área superficial, dividindo o valor do custo total em um sistema de classificação e classificando as áreas conforme seu uso. Um projeto hipotético foi usado para a demonstração inicial. Posteriormente, foi realizado um estudo de caso real em colaboração com uma construtora portuguesa. Como resultado, foi possível gerar uma estimativa de custo dentro de um ambiente BIM para os estágios iniciais utilizando banco de dados histórico de custos como fonte de informaçõe. Foram feitas considerações sobre as escolhas de modelagem do projeto anterior e do amplo uso e benefícios possíveis decorrentes da aplicação do trabalho proposto. Palavras chave: (5D BIM, Estimativa de Custo, Estágios Iniciais, Informações Históricas, Modelagem da Informação da Construção) BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ vii ABSTRACT The BIM methodology is revolutionising the way the construction market works, leading to the desired digitalisation and automatization throughout the whole life cycle of a project. It consists of the combination of three fields: technologies, policies and processes. Together, they work as a shared knowledge resource for information, allowing to manage it, forming a trustful source of data for decision making and also making it possible for all the stakeholders to collaborate along all the processes beginning from the very first step of the project. Besides, BIM also covers which data is managed in terms of creation, use, reuse and application into digital models aiming the development and improvement of the design, construction and operation of one or several projects. Among all the possible uses for the BIM methodology, there is support for cost management linking the cost information with the 3D Model. This use is commonly known as the 5D BIM. Project cost management is the process involved in planning, estimating, budgeting, financing, funding, managing and controlling costs, seeking to finish a specific project within the approved and desired budget from the client or sponsor. The cost estimation is among the most critical preliminary processes in any construction project. A high initial cost estimate can lead to a discouraging process for the client to proceed with the project. Alternatively, a too low-cost estimation could lead to financial problems during the subsequent stage. The floor area method is the most used method for preliminary cost estimates. However, it is a prediction and should not be considered as the final cost. During the early stages of the project, the quality and amount of data made available regarding the project are frequently low or not defined, leading to several assumptions. The use of historical data could fill the gap left by the lack of information. However, the traditional detailed cost estimation approach is a high demanding workload and time-consuming task. This dissertation proposes a BIM-based cost estimation for early stages of the project based on historical cost data provided by prior projects and its subsequent storage into a cost database. Through research in academic articles, master dissertation, PhD thesis, cost and BIM books and guidelines, challenges for cost management during the early stages of the project lifecycle were identified. Among the objectives were the easily updatable cost estimation according to layout changes and to provide the possibility of updating the cost estimate as the BIM model evolved. Therefore, a workflow was developed using an adaptation of the floor plan area method, dividing the total cost value in a classification system and classifying the areas according to their use. A hypothetical project was used for the initial demonstration. Afterwards, a real case study was also performed in collaboration with a construction company from Portugal. As a result, it was possible to generate a cost estimation within a BIM environment for early stages using a cost historical database as a source of cost information. Considerations were made regarding the modelling choices of the previous project and the wide possible use and benefits arising from the application of the proposed work. Keywords: (5D BIM, Building Information Modelling, Cost Estimation, Early Stages, Historical Data). BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ viii TABLE OF CONTENTS 1. INTRODUCTION ............................................................................................................ 12 2. REVIEW OF THE STATE OF ART ............................................................................... 16 2.1. BUILDING INFORMATION MODELLING – BIM .......................................................... 16 2.1.1. BIM Definition ............................................................................................................. 16 2.1.2. BIM Concepts related to models and elements. ............................................................ 17 2.1.3. Dimensions ................................................................................................................... 19 2.2. BIM AND COST MANAGEMENT .................................................................................... 20 2.2.1. Cost management ......................................................................................................... 20 2.2.2. 5D BIM......................................................................................................................... 23 3. BIM-BASED COST ESTIMATION ................................................................................ 26 3.1. INTRODUCTION ................................................................................................................ 26 3.2. SELECTION OF SOFTWARE AND ITS APPLICATION ................................................. 27 3.2.1. Autodesk Revit ............................................................................................................. 27 3.2.2. Microsoft Excel ............................................................................................................ 27 3.3. CHALLENGES DETECTED WITHIN THE CONSTRUCTION INDUSTRY .................. 28 3.4. OBJECTIVES OF THE WORKFLOW ................................................................................ 29 3.5. WORKFLOW ...................................................................................................................... 31 3.5.1. Calculation method ....................................................................................................... 32 3.5.2. Historical Data .............................................................................................................. 34 3.5.3. Modelling ..................................................................................................................... 38 3.5.4. Cost estimation and Planning Validation ...................................................................... 44 4. CASE STUDY .................................................................................................................. 48 4.1. INTRODUCTION ................................................................................................................ 48 4.2. COLLECTING AND ORGANIZING THE HISTORICAL DATA. .................................... 49 4.3. GENERATING PROJECT INFORMATION FOR COST ESTIMATION. ......................... 55 4.4. RESULTS ............................................................................................................................. 56 4.5. CONSIDERATIONS............................................................................................................ 59 5. CONCLUSIONS .............................................................................................................. 62 REFERENCES......................................................................................................................... 64 LIST OF ACRONYMS AND ABBREVIATIONS................................................................. 67 BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ ix LIST OF FIGURES Figure 1 - BIM diffusion Dynamics (Succar, 2019). ............................................................................ 12 Figure 2 - Common connotations for several BIM terms (Succar, 2009) ............................................. 16 Figure 3 - Some explanations of each BIM acronyms letter (Azhar et al., 2015) ................................. 17 Figure 4 - Type properties and constraints of a cupboard modelled in Revit. ....................................... 18 Figure 5 - Sample of a structural model designed in an object-oriented software (Adapted from Sandoval et al., 2019) ........................................................................................................................... 19 Figure 6 - BIM Dimensions.................................................................................................................. 20 Figure 7 - Cost management tasks in the context of the RIBA Plan of Work (Lu, 2018) ..................... 21 Figure 8 - Estimate accuracy according to the project stage (adapted from (Potts, 2008)). .................. 22 Figure 9 - Methods of initial cost estimating (Ashworth and Perera, 2013). ........................................ 23 Figure 10 - Sample of BIM 5D software (Trimble, 2019) .................................................................... 24 Figure 11 - Steps for generating the cost and construction term estimation. ........................................ 26 Figure 12 - Planning and cost challenges through the defined stages. .................................................. 28 Figure 13 - Generating, storing and reusing cost information. ............................................................ 29 Figure 14 - Objectives according to each stage. ................................................................................... 30 Figure 15 - Workflow developed ......................................................................................................... 32 Figure 16 - Historical data organization in Microsoft Excel ................................................................. 36 Figure 17 - Filling bedroom information for Portugal and High standard ............................................ 37 Figure 18 - Cost values according to each room, region and project standard ...................................... 37 Figure 19 - Historical productivity data................................................................................................ 38 Figure 20 - Architectural template selected on Revit ........................................................................... 38 Figure 21 - Project units defined on Revit software ............................................................................. 39 Figure 22 - Importing options of the source of information. ................................................................ 39 Figure 23 - Generating the floor plans .................................................................................................. 40 Figure 24 - Ground floor areas ............................................................................................................. 41 Figure 25 - First and following levels layout ........................................................................................ 41 Figure 26 - Creating the schedule ......................................................................................................... 42 Figure 27 - Final schedule containing floor area data ........................................................................... 42 Figure 28 - Schedule configuration ...................................................................................................... 43 Figure 29 - Export process and configuration utilized .......................................................................... 44 Figure 30 - Project information imported as a table in Excel ............................................................... 44 Figure 31 - Process of data quality check ............................................................................................. 45 Figure 32 - Selection of the location and standard considered.............................................................. 46 Figure 33 - Sum-up of the project areas ............................................................................................... 46 Figure 34 - Estimations for Portugal .................................................................................................... 47 Figure 35 - Estimations for Spain ......................................................................................................... 47 Figure 36 - Initial and final room classification.................................................................................... 51 Figure 37 - The floor plans -1, and 0. ................................................................................................... 51 Figure 38 - The floor plans 1,2,3 (left) and roof (right) ........................................................................ 52 Figure 39 - Hotel Room’s windows selected in the schedule and highlighted on the floor plan .......... 53 BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 16 2. REVIEW OF THE STATE OF ART 2.1. Building Information Modelling – BIM 2.1.1. BIM Definition BIM methodology is gaining position inside the AECO (Architecture, Engineering, Construction and Operation) sector and is one of the technologies trending in the construction industry (Kulasekara et al., 2013). However, the definition of this methodology is commonly misunderstood by the user and professionals of the sector. Even if the term BIM is well accepted and widespread, its meaning and the exact words that form it are not a consensus between the academia and industry. BIM could be the acronym for Building Information: Model (Kim et al., 2013), Modeling (Sacks et al., 2018) or Management (McArthur, 2015). Figure 2 shows some common connotations for the multiple BIM Term. Figure 2 - Common connotations for several BIM terms (Succar, 2009) Besides, many professionals link the BIM methodology as the use of software capable of designing their projects in a 3D form. This fact may be attributed to the fight between the software developers in the 2000s. The big software developers at that time tried to be the first one to develop software containing the rising new future of the design and construction data management (Chuck et al., 2008). Another possible reason is related to the benefits of the adoption of the BIM methodology which can only be felt when its processes, premises and concepts are interpreted by software, processing and filtering the information according to the desire of the user (Lino et al., 2012). However, this understanding is not complete. This definition could be considered as part of the entire BIM. The functional definition of BIM is a combination of the three fields: technologies, policies, and processes (Succar, 2009). It works as a shared knowledge resource for information, allowing to manage it, forming a trustful source of data for decision making and also make possible to all the stakeholder to collaborate during its life cycle from inception onward (BuildingSMART, 2015). Beyond this, the pragmatic definition is that BIM works as a common language with many dialects for the entire construction industry, allowing to discuss and learn about the construction industry innovation all around the world (Succar, 2009). BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 17 Likewise, BIM is a digital representation of physical and functional characteristics of a facility (BuildingSMART, 2015) and process which data is managed, in terms of creation, use, reuse and application into digital models with the purpose of development and improvement of the design, construction and operation of one or several projects (Sacks et al., 2018). It is an intelligent simulation of the project and its characteristics. To enable the achievement of the integrated project delivery, are necessary to achieve, at least six key elements: digital, spatial, measurable, comprehensive, accessible, and durable. Clustering it allows to quantify, query, communicate, assess constructability, sequential and financial aspects of the project, interoperable between different tools and stakeholders and maintain the track and integrity of the data during all the phases of a facility’s life (Campbell, 2006). Figure 3 - Some explanations of each BIM acronyms letter (Azhar et al., 2015) According to the definitions above, it is a consensus that BIM is much more than just software, and with the BIM implementation comes significant changes regarding the workflow and the project delivery processes inside the company/project (Hardin and McCool, 2015). Another possible change which came together with the BIM implementation is the Integrated Project Delivery (IPD), which is a project delivery approach to improve the collaboration between all the stakeholders integrating people, systems, business structures and best practices. Together, they optimize the process to reduce waste during the whole lifecycle of the project, anticipating decisions and spreading valuable information thought at the early stages of the project (Glick and Guggemos, 2009). 2.1.2. BIM Concepts related to models and elements. Although the project desires to keep all the information in the same place to avoid redundancy and inconsistences, the sources of information are often from different stakeholders. To achieve this goal, inside the BIM methodology has mainly two different characterizations for the models of a project, the federated and coordinated models. A federated model is characterized as a distinct individual BIM model, which does not affect automatically other federated models, nor is affected by. The several federated models are linked and interact exchanging data among them, even though a change into one model impact the others, does not change automatically other federated models, reinforcing the distinction among them and the ownership of data. Usually, each discipline has it own federated model (e.g. architectural, structural), with the exception in big projects when is necessary to create several federated models within the same discipline, due to the better management. In this case, they are called volumisation model. On the other hand, the coordinated model is characterized by the merge of BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 18 several federated models, with the purpose to gather all the information and perform an integrated analysis of the status of the project, such as clash detection and constructability assessment (Cerovšek, 2019). In terms of modelling, while the computer-aided design (CAD) approach is to design the object made by several lines, forms and text, the BIM methodology consists of the object-oriented approach. This method consists in model the object in an identical organization as the object exists in the real world, imputing information, classes, relationships, and characteristics of the object into a data structure database. It allows the interaction with other elements, enabling the use and filter of this information by demand of the user activity. Besides, with this approach, the user is possible to input not only geometrical information about the object but also information regarding developer, fabricant, clearance areas, costs, properties and other information required by the user (Sousa et al., 2011). The oriented-object approach also reduces inconsistency and rework during the process. Once the object is created, this data is stored and allow reusing the same information inside the same or other projects and software. One sample is when you design an object “wall”, and after it is generated a floor plan, 3D view and a quantity take-off, the software gets this information from the database. Therefore, when a change is performed on its parameters (e.g. length or height), it is automatically updated in all the floor plans, views, and quantity take-offs (Azhar et al., 2015). Figure 4 - Type properties and constraints of a cupboard modelled in Revit. The introduction of the parametric design and relations is also one of the benefits of the BIM methodology, changing from the documentation that was only understandable by humans for new data representations which computer can also interpret (Jeong et al., 2009). As a consequence of the parametric design and relations, now each element from the model has internal and external predefined rules to follow, establishing connections and behaviours for the interaction between elements and classes of the model (Sousa et al., 2011). Internal are the ones defined within a class of object (e.g. the minimum or maximum length of a cupboard, as shown in Figure 4). The external is the relations BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 19 between two objects or classes (e.g. during the structural design, the column and beams are smart enough to do not create an overlap between the elements, avoiding an error for the quantity take-off or properties of the elements). This object-oriented design is shown in Figure 5. Figure 5 - Sample of a structural model designed in an object-oriented software (Adapted from Sandoval et al., 2019) The result of these rules is that the computer now can analyse the relations between several and different objects while the user is doing the changes. If any rule is broken, the software does not finish the changing process. In case of a change that impacts other objects, the model adapts automatically according to pre-established rules between the elements, avoiding systematic errors and a very timeconsuming checking of the model (Poças, 2015). 2.1.3. Dimensions Besides the BIM Uses, there is also the definition of BIM according to dimensions. The dimension 2D and 3D are the more familiar use of BIM and usually the first benefits of the use of the BIM methodology. The dimension 2D consists of bi-dimensional drawings, such as floor plans, elevations and sections (Poças, 2015). The 3D dimension consists in the three-dimensional model expressing the design concepts, the parametric modelling, collision detection and model walkthroughs visually. (Charef et al., 2018). However, the BIM adoption allows to go further than only the 2D and 3D geometrical representation, as shown in Figure 6. It also allows performing other analysis regarding essential procedures and stages of the project, which was elaborated in a non-connected way before (Poças, 2015). To enhance the use of the three-dimensional structure of BIM, new ways of approaching the tool have been implemented over time (Gledson and Greenwood, 2016). BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 20 The visualisation and benefits brought by the 3D BIM started to be not enough to the industry, and better uses began to be defined by new dimensions of the BIM application. The responsible that are dictating these dimensions are mainly the researchers and the users of the methodology. The dimensions 4D and 5D, have a well spread and accepted definition for 3D model + time and 3D model + cost, respectively. However, the dimension 6D and 7D present some contradictions in academia and practitioners (Charef et al., 2018). The National Building Specification (NBS) defines the dimension 6D as a dimension where information regarding facility management and operation activities are included into the model (McPartland, 2017), nevertheless within the academia some articles and for some practitioners using the 6D dimension is also defined as sustainability (Charef et al., 2018) (Yung and Wang, 2014). Figure 6 - BIM Dimensions Due to their importance within the present work, the BIM 5D definition will be covered and explained in more detail in the following sub-chapters. 2.2. BIM and Cost Management 2.2.1. Cost management The Project cost management is the processes involved in planning, estimating, budgeting, financing, funding, managing and controlling costs seeking to finish a specific project within the approved budget from the client or sponsor (PMI, 2017). Among these processes are: 1. Plan Cost Management – In this process are defined how the project cost will be estimated, budget, managed, monitored and controlled. 2. Estimate costs – The process of forecasting the approximate amount of cost needed to complete a specific task or project work. 3. Determine Budget – The process of cluster all the costs of all individual tasks/project work to generate a cost baseline. 4. Control costs – The process of monitoring the cost of the project, analysing the forecast cost and updating it if needed (PMI, 2017). BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 21 Cost management within the construction industry also relates to all cost-related activities since the start of the project until a successful building occupation, operation and maintenance (Ashworth and Perera, 2013). The cost management has several steps according to which stage of the project. It is undertaken in almost all the phases of a project, even considering that the activities can significantly vary. The cost management lifecycle starts together with the cost estimation during the preparation phase and least until the construction project complete. (Lu, 2018). Figure 7 demonstrates some of the tasks and responsibilities according to the stages defined by the RIBA Plan of Work. Figure 7 - Cost management tasks in the context of the RIBA Plan of Work (Lu, 2018) The process of cost estimating is prepared and started as early as the company requires and should be revised and updated at many stages throughout the project. Considering it is a prediction, it should not be considered as a final cost, and it has the characteristic not to be 100% accurate (Potts, 2008). The most essential criteria for acceptance for cost estimation is accuracy. During the early stages of the project, the quality and amount of data made available regarding the project are frequently poor or not defined, leading to the assumptions and considering characteristics of similar previous projects. The impact of misunderstanding these characteristics could bring considerable effects on the stakeholder’s perceptions of the project and sometimes even derail the project in economic terms. A high initial cost estimate can lead to a discouraging process for the client to proceed with the project. Alternatively, if the estimation is too low, it could lead to financial problems during furthers stage. Considering that the cost estimation of a construction is a probabilistic activity, is preferable to show a range of estimated sum or an explicit value margin rather than a fixed amount (Ashworth and Perera, 2013). Figure 8 shows a base for the acceptable estimate accuracy according to the stage of the project. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 22 Figure 8 - Estimate accuracy according to the project stage (adapted from (Potts, 2008)). The cost estimate under preliminary and feasibility stages usually prove to be less accurate but quicker than in the other. This process also relies on the experience and expertise from the professional who is performing the task, the historical cost data gathered in the company from similar and previous projects (Lu, 2018). Besides, the preliminary cost estimation should also consider the work term, the location of the project and which is the use and standard of the project (Potts, 2008). In order to perform the cost estimation, a starting point is to define which method will be applied in the process. Several methods are widely used in the construction and other industries around the world. Thus, more than only accuracy other parameters should also be considered during this decision, such as how the information is related to the project, what is the time available to the estimation and how is the historical data stored (Ashworth and Perera, 2013). Figure 9 shows some methods generally used for initial cost estimates. Among the techniques shown in Figure 9, the most commonly used are the superficial method, unit method and approximate quantities method. The superficial method, also known as “Floor area method”, is the most used method for preliminary cost estimates. This method is fast to calculate, and also it is shown in a very perceivable way for all involved stakeholders. It consists of measuring a total area of all floors of the project in case and multiply by a historical unitary cost appropriate from similar previous projects. In order to have a comparison and a benchmark line among the projects, the floor area is calculated from the internal dimensions of the building. The historical unitary cost could be provided by former projects from a client, within the historical database from a company or from official data for unitary building cost provided by local institutions (Ashworth and Perera, 2013; Lu, 2018). The unit method, also known as “Cost according to building function”, consists in the selection of a standardise function unit for the project and multiply it by a historical base cost per unit. Usually is selected the best function to describe the use of this project. This method considers a close relationship between the cost of construction and the functionalities provided by the project. Some samples for the standard units are: (1) Beds, in case of a hospital project, (2) Car spaces, in case of Car Parking Project and (3) student, in case of a School project. This method is useful for estimating public and national buildings programs, in which it is necessary to have some comparability in the unit cost. (Ashworth and Perera, 2013; Lu, 2018) The approximate quantities method consists of cost composition items which are measured combining or grouping specific bill-measure items. Even though this method has the characteristic to provide a more detailed cost estimation than the others, it is a very time and effort-demanding method. The BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 23 composition or grouping are performed according to the experience of the surveyor and require more information from the project. This method suits better to a more advanced stage of the project rather than at an initial phase. Thus, this method is more effective and used in practice when there is the possibility to analyse the complete project documentation at first, mainly in public tenders or big projects tendered with the design stage finished (Ashworth and Perera, 2013; Lu, 2018). Figure 9 - Methods of initial cost estimating (Ashworth and Perera, 2013). 2.2.2. 5D BIM The importance of the cost estimation during all the stages of a project has been widely recognized and performed. However, the traditional cost estimation approach is a very workload and timeconsuming task, leading to results with low accuracy and reliability, which may cause disastrous costs overrun and project delay. In order to help this problem, one of the existing solutions is the application of the 5D BIM. It consists of the 3D model with the addition of the cost information (Cho et al., 2010). This BIM use leads to more precise cost estimations since the early stages and together with the automatic quantity take-offs allows a better understanding of the impact of changes and decision making during all the stages (Sacks et al., 2018). Using 5D Models also provides a better evaluation of alternatives scenarios and different approaches for the same project, allowing better decision making BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 24 during all the project lifecycle. Figure 10 shown a sample of 5D BIM software while performing the cost management together with the 3D visualisation of the project. Furthermore, (Wang et al., 2016) developed a model that utilises BIM to create a project budgeting curve, namely, an S curve. This model generates an optimised cost budget curve based on multi-criteria, making it more reliable in implementation and giving a realistic indication concerning cost/schedule cases. Figure 10 - Sample of BIM 5D software (Trimble, 2019) Among the main advantages and uses of the 5D BIM Uses and stages are the quantity take-off, cost estimating, cost budgeting, cost control, life cycle cost analysis and claims (Vigneault et al., 2019). The use of BIM models allows for faster and more efficient quantity take-off reports and material needs schedules. Besides, the combination between the bill of quantities extracted from the model and the visual analysis of those same quantities result in an optimized report, carrying fewer errors and improving the overall visualization of the project. However, BIM models hardly contain all the necessary information to enable a complete and correct quantity take-off automatically (Nadeem et al., 2015). Some quantities of the project cannot be extracted from the model for several different reasons, such as current tools capabilities, how the information was structured in the model or due to lack of modelling some objects (Monteiro and Martins, 2013). Thus, during the quantity take-off process will still be needed to the use of indicators for some quantities, modelling of missing information or experience to validate the generated report (Chuck et al., 2008) Utilizing the quantity take-off provided by the selected BIM solution, it usually allows the user to register the unitary cost to each resource/activity, generating the cost estimation (Azhar et al., 2015) It BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 25 usually also contain features allowing the user to link the quantity take-off to an external database to implicate in a less manual and faster task (Sacks et al., 2018). This link between the model and an external cost database also enables the possibility to generate alternatives in terms of cost and resources, demonstrating a more realist expectation of the project. Moreover, it improves the client and all stakeholders understanding of the project and the impact of their decisions related to cost (Olatunji et al., 2010). Further in the project, it is also an important step to consider real prices from subcontractor’s quotes to the model, generating the Cost Budgeting. Cost control should be performed regularly, updating the cost data, and analysing different economic indicators and generating reports. Automated cash flows analysis developed with the use of 5D BIM allows faster and more precise cash flow forecasts at early stage of the project. Besides, the current cost data can then be compared to the previously modelled cash flow to evaluate the variance between the actual costs and the budget, identify the most cost impacting elements and assess the probable final cost of the project (Sacks et al., 2018) Procurement purchasing 5D BIM tools capabilities now allow the purchasing of elements directly from the model, since the objects modelled represent what needs to be acquired. Users are then able to use models developed by product manufacturers containing all the necessary specifications for quantity take-off, material schedules and cost estimating (Chuck et al., 2008) 5D BIM also allows the user to select a particular period to verify the completed task and select its elements, the related cost and validate the information regarding the subcontractor progress and compare its progress with the paid amount (Olatunji et al., 2010). BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 32 be organized and filled or exported to an external cost database. In this database, the information will be stored and ready to be used by future projects. As many previous projects as possible should be imported into this database, in order to provide a more solid basis for future estimates. With the database filled, the next step is to generate the project information to provide the estimated cost. At this time, it is necessary to use the BIM methodology for the workflow to work. The information must be exported from the selected BIM authoring tool to the database containing information from the project rooms. After that, the database will correlate the historical costs of the old projects with the rooms of the new project and will generate the desired cost estimate. All of these steps will be explained in detail and demonstrated through the hypothetical case study developed in the next sub-chapters. Figure 15 - Workflow developed 3.5.1. Calculation method Several different approaches were analysed and were decided to apply the Floor Plan Area method for the estimation methods. According to (Ashworth and Perera, 2013), this is the most used and spread method for cost estimations among the construction industry. Usually, this method consists in sum the total floor plan area of the project and multiply it by a fixed average cost for the building use or purpose. The most significant benefits of this method are that it is fast to generate a cost estimation and easy for understanding the source of information. However, this method applied conventionally does not consider any other project information rather than the use and the total floor area. Besides, this average cost data is usually provided by market analysis or the average of construction costs from the project’s local area and not the specific historical data from the company performing the cost estimation. Equation 1 presents how the cost is estimated applying the conventional floor plan area method BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 33 (1) Where: CE = Cost estimation; FPA = Floor plan area and UAC = Unitary Area Cost. To consider more project information, the method was adapted to consider more information during the cost estimation process. The idea of sum the area and multiplying it by an average value will be maintained. Still, the information will no longer be unique and general for the entire building, but a sum of values considering the internal layout of the project and the cost composition of each room. Instead of just two values multiplied, the FPA and UAC were now defined according to the internal use of the project. For example, in the case of a residential building, the systems contained in a bedroom and a bathroom are different, leading to different costs. For the proposed workflow, the bedroom and the bathroom have different values for the FPA and UAC, resulting in a cost estimation by each internal area. The total cost estimation is the sum of all the cost estimation of each internal area of the building, as shown in Equation 2. Considering these differences in the calculation method allows a more specific estimate for each project. Besides, as in the conventional method is also necessary to sum up all areas of the building, it is possible to generate a more specific cost estimate than the conventional method with the same time dedicated to this activity. Moreover, it is now also possible to carry out the estimation of several different scenarios of internal layouts for a project, even if the total value of the floor plan area does not change. This feature is of great value to support decisions making during the proposed stage for this workflow. During the initial stages, it is very common to made changes in the internal layout of the projects due to several factors, for example, requirements of public bodies during approvals, problems with the terrain, optimization of internal areas, decisions on construction techniques, changes in the needs of the client, financing and funding difficulties, among others. With this new approach, it is possible to demonstrate the consequences of the cost of the changes made more quickly. With this, the decision has more support to be performed in a more agile way. (2) Even though the information generated has an excellent value for layout analysis at early stages, it is still not sufficient to achieve the objective of generating useful information for the next stages of the project. Although it allows the analysis of several different scenarios, it still does not allow its continuous updating as the project's modelling process advances. For this, the format of the unit cost of each area was adapted. Instead of applying a fixed value for each area, this value was segregated according to the systems needed to build the specific area. For example, in the case of a room, the conventional method would only use the cost information per square meter of the room. However, the actual information generated is a total value, not showing how each system impacts the cost. Thus, it is not possible to update this information when only one system is detailed, only after the entire project BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 34 has been completed. In the proposed workflow, the value of each system contained in the room is considered. After this breakdown, it is possible to generate the project cost estimate not only as a final value but also as a sum of the cost of the construction systems. In this way, it is possible to generate a forecast of which systems will have the most significant weight on the cost of the project. This information support different decision-making by different project stakeholders, such as which will be the first systems to be modelled and detailed. The user's specific historical database provides all information related to the organization of the project areas, costs and how the project systems will be characterized. This is a crucial step in the process, as the amount of effort required to prepare historical information is proportional to the level of detail and complexity desired for the estimate. Thus, the organization of the areas and the classification system defined will be used for both cost estimation and planning validation. Although there are classification systems for civil construction, the information generated using them would not be used efficiently if the user has all his historical information and cost management defined in his own system. Also, it would be against the objective of allowing the user to have flexibility in generating and updating their cost estimates if a specific area and classification system is determined. As mentioned by (Cho et al., 2010), the cost and planning information is usually generated in a nonintegrated form, leading to time-consuming updates. To solve this constraint, the workflow was developed considering that the specific information about the project for the cost estimation and validation of construction planning is the same. Therefore, for planning validation, the floor plan area method was also applied and adapted. The same area classification applied for the cost estimate will be used. As described above, the objective related to the planning is not to generate a sequence of tasks automatically, but rather to validate whether the desired construction term is consistent or not with the historical basis of productivity and available resources. This validation is done in the same classification system used in the cost estimate. However, historical productivity data is usually measured at its main unit and not by floor plan area. For example, the measured productivity of the masonry service is measured by the square meter of masonry performed per day, and not by the daily square meter of masonry per floor plan. To solve this problem, a conversion rate was applied to bring the productivity of all systems to the same unit of the method. This information is often not available and requires a more in-depth analysis of previous similar projects. After obtaining a conversion rate for each system, the available amount of resources and the average productivity, it is possible to estimate the duration of execution of each system and validate if the construction term is executable or not. The activities to perform the estimation and validation were divided into four different significant steps: organizing the historical data, modelling the information, the calculation of the cost estimation and the planning validation. A hypothetical project and historical data were used to elaborate and prevalidate the workflow before the study case. 3.5.2. Historical Data The workflow started with the preparation of the historical basis to be used in the following steps. Some considerations were made before starting to fill in historical data: BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 35 • It is necessary to know the desired level of detail for the cost estimate. How the historical base will be clustered is directly linked to this. When higher accuracy is aimed at, more detailed clustering of the data is required. In addition, the quality of the output of the workflow is dependent on the quality of the historical basis. A large amount of poorly analysed and poorly accurate data will lead to an estimate with low reliability. • Caution to highly detailed estimates at such an early stage was taken. Although it is possible to have a great degree of detail through this workflow, it was not developed to generate a bill of quantities, but cost estimation according to the construction system based on the specific layout of the project. • The time required for organizing and filling in the historical base is exponentially linked to the determined estimate level of detail. Non-useful information desired in excess, which will not be used in future stages, leads to wasting time and efficiency during the workflow. • When deciding which areas to register, it is worth remembering that the output is a cost estimate at an incredibly early stage of the project, so areas with small differences characteristics do not necessarily need to be separated. • The workflow was developed allowing the evaluation, correction, updating and addition of new systems and areas in an organized, direct and straightforward way. Therefore, do not stick to several specificities at the beginning of the process. After these considerations, it will be demonstrated with the hypothetical project how the workflow was developed by means of which are the necessary historical data inputs and how the information is handled automatically. Having as starting point the historical data inputs, two more variables were selected besides the room and classification system mentioned above. This information is related to the region in which the project will be carried out and its quality level. The database was designed in such a way that each region and quality level contain its relative cost. Although it does not lead directly to a more accurate cost estimate, it allows the use of the same historical database to projects in different countries and from different standards. Moreover, it supports also to compare the estimations for the same project in different countries. This is of great value for multinational companies and the ones with a wide range of products. The separation of the areas was done through 11 different types of areas corresponding to common uses, namely: bedroom, suite, kitchen, bathroom, hall, living room, circulation, elevator, parking place, external parking and outdoor leisure area. The classification system adopted was divided into 14 different systems, namely: initial services, foundation, structure, roof, walls, plumbing installations, electrical installations, HVAC installations, floor finishing, wall finishing, ceiling finishing, façade and door and window systems. Considering it is a hypothetical project, the area and system classification were based on the background experience of the author within cost management. For the example purposes, the regions were divided into two: Portugal and Spain, Finally, the project standard into High and Medium. Figure 16 shows how the initial information was organized in the Microsoft BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 36 Excel sheets. In order to organize the information, all the inputs cells needed to be typed by the user were filled with grey colour. All the cells with values and filled with white colour are calculated automatically. Figure 16 - Historical data organization in Microsoft Excel After defining all the variables to be considered in the workflow, the historical data was filled out, relating all these characteristics. As mentioned above, the number of values to be filled is proportional to the variables. The defined way led to 616 different cost information. Figure 17 exemplifies how the historical cost data for a bedroom was filled, for Portugal and considering a High construction standard. Note that the information provided is the cost according to each system. The spreadsheet will consider the values in this way to perform the cost estimation calculation, but this way makes it difficult to assess whether the values are correct or not. To solve this, the values of all systems were grouped, in order to show the final unit costs of each area. To achieve this, conditional values search, sum and logic formulas were used in the historical cost database. The final form of these grouped values is shown in Figure 18. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 37 Figure 17 - Filling bedroom information for Portugal and High standard Figure 18 - Cost values according to each room, region and project standard For the historical data related to planning was characterized in another format. As mentioned above, the information required for the planning validation is the conversion rate to transform the quantity of services from its original unit to square meters and daily productivity. The daily productivity was calculated by the daily individual productive multiplied by the number of available resources. The total daily production was calculated, applying the conversion rate to daily productivity. The available resources data is only required to calculate daily productivity data; however, they were filled together, considering that this is a theoretical validation. Figure 19 shows how the data was presented and organized. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 38 Figure 19 - Historical productivity data Now all the necessary historical data for the workflow has been filled. The way it will be automatically processed by the software according to the project information will be explained in the sub-chapter of cost estimation and planning validation. The next step of the workflow is generating the project data by the modelling process. 3.5.3. Modelling The modelling process of the proposed workflow was performed in the software Revit 2020. It was developed so that it does not have several steps that are time-consuming and is focused on generating only useful information for the workflow. At this point, it is not necessary to focus on graphical and non-graphical information on the model, but on generating the information necessary for the application of the method. Although these are of great value, they will not be used and applied at this specific stage. When starting the Revit 2020 software, the default Architectural template of the software was selected, as shown in Figure 20. As the method is based on the floor plan area, it is essential to check which are the project units considered in the software. An important step is to check if the project area unit and rounding considered in the project is the same than the used in the database, as shown in Figure 21. The entire database is organized using the mentioned unit. If the extraction of the information from the BIM model does not follow the same organization, it will lead to incorrect cost estimation. Figure 20 - Architectural template selected on Revit BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 39 Figure 21 - Project units defined on Revit software With the unit and format defined, the modelling process itself was started. The modelling process is impacted as the client initially generated the project layout. The Revit software allows the link and import of several different formats, for example, its native format RVT, IFC, CAD, XML, PDF and images, as shown in Figure 22. For this hypothetical project, it was considered that the modelling would start from the beginning, without any link or import. Figure 22 - Importing options of the source of information. To define the project areas, the “Rooms” feature of the software was used. “Rooms” are considered a model element in Revit, like walls and door. In this way, it is possible to add the graphical and nongraphical information needed in this element. This feature allows you to create and detail reports which describe the areas defined in plan views. Revit considers a “room” to be a subdivision of a project area, based on boundaries elements, such as walls, floors and roofs. The software also allows the use of room separation lines to subdivide spaces where there is no physical division through border elements. The moment the border element is added, moved or deleted; the dimension of the “room” is updated automatically. It is also possible to pre-define room names in the software before placing the wall or other border elements in the model. In this way, the first step was to add the specific areas contained in the project. Afterwards, the rooms inside the software were created. As it is only allowed to place rooms in a plan view, the project levels and their respective floor plans were generated, as shown in Figure 23. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 40 Figure 23 - Generating the floor plans With the generated floor plans, the process of modelling room-bounding elements began. As a way to test the resources, it was decided to use both walls and room separation lines as delimiters. The external bounding was modelled as walls and all internal divisions with the room separation line. As this example is hypothetical, it was not considered a real layout of a project, but only areas for the continuity of the workflow. After modelling the elements walls and room separation lines, the command “Place rooms automatically” was used to generate all areas automatically. Afterwards, the names of each area were changed according to their use. A visual legend tool based on the name was added to make a visual check of areas were. These were divided into internal and external areas of the building on the ground floor. Figure 24 shows how the model looks after all these steps were performed. The same process was carried out for the first floor, only differentiating the internal areas in order to generate a more realistic example. At this moment, the necessary information about the project to estimate the cost and validate the execution time of the work has already been elaborated. The next step was to organize this information in a standardized way and export it. It was performed using the schedule/quantities feature and selected the category Rooms for the schedule, shown in Figure 26. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 41 Figure 24 - Ground floor areas Figure 25 - First and following levels layout BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 48 4. CASE STUDY 4.1. Introduction The caste study was performed in collaboration with a big construction company from Portugal. The company is one of the largest in the construction sector in Portugal, maintaining a family-owned enterprise characteristic. With a consolidate presence in the domestic market, the Group operates in 16 different countries around Europe, South America, Africa and Asia. The company is partners of the BIM A+ master and were since the beginning collaborating with the development of the proposed dissertation. For the case study, two different projects with similar characteristics were used. The project for collecting and organizing historical cost data is related to the construction of a hotel with a capacity for 112 rooms, located in the south-central region of Portugal. The total project will be distributed over four floors, the first being underground. On the first two floors are located the areas of parking and technical areas, lobby, reception, breakfast areas, living areas, toilets and some bedrooms, while the last two were intended for the exclusive use of bedrooms and support areas to supply the customers. In addition, it contains an external area on the ground floor. The company was responsible for the general construction and design of some disciplines of the project. Due to it, part of the systems was modelled and developed under the BIM methodology for, while others were developed using CAD-based solutions. Also, the company uses a specific software called Candy CCS for cost management. Information related to the design of the structure and architecture specialities was delivered in a BIM model, while the MEP and HVAC specialities were made available in CAD format. Information related to the total cost was delivered using Excel spreadsheets, directly exported from the CCS software. The project to be carried out the cost estimation is for the same client as the previous project. Its use is also for the hotel and located in the same region in Portugal. This project is in the final stage of its architectural design, while the cost estimate and budgeting are in progress. The files for the project were provided in CAD format, containing their floor plans and sections. The design and modelling of the other systems related are under development. The project selected to be applied to the workflow developed fits perfectly in the stage proposed by the dissertation. The project is at the early stage, with decisions related to layout and construction techniques still in progress. At this time, the information is still very susceptible to change. Still, a cost estimate is necessary to have a better understanding of the estimated budget needed to construct the project. With the historical cost base organized in the database, took less than one day to be prepared the information within the BIM tool, export to the database and generate the cost estimation by the dissertation author. During the next sub-chapters, the steps and difficulties faced during all stages were demonstrated, since the selection and adaptation of the classification systems, adaptation of the current cost BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 49 spreadsheet to the database, modelling, exporting the layout data into the database and the generated cost estimation. 4.2. Collecting and organizing the historical data. The construction company provided the data related to the cost and design of the Project 1. The information was contained in BIM models in RVT format, spreadsheets with the total cost of the project in xls format and drawings in CAD format. To apply the proposed workflow, it was necessary to organize the project’s data into structured floor plan areas and their relative costs separated into defined systems. The first task was to define the classification system adopted for the workflow. The company has already developed and adopted its own classification system for cost management and, to produce useful information for the next stages, thus this was adopted as a basis and some adaptations were made. The classification consisted of 6 major groups, namely structure, architecture, hydraulic installations, electrical installations, mechanical installations and HVAC, as shown by Table 1. However, the architecture group contained 48% of the total costs of the project and was comprised of several different groups of activities. Therefore, it was decided to replace the architecture group with its subgroups, grouping them based on similar characteristics, so as not to have an excessive number of classifications. The classification system adopted contains 18 systems and is shown in Table 2. Table 1 - Company classification system and its totals Item Systems Amount % EST Structure € 874,772.94 19.4% ARQ Architecture € 2,178,225.96 48.3% HID Hydraulic instalations € 392,980.11 8.7% IETS Electrical installations € 509,256.24 11.3% IE Mechanical installations € 40,521.64 0.9% VC-GTC HVAC € 518,189.98 11.5% Total: € 4,513,946.87 100% BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 50 Table 2 - Final classification system and its totals Number Systems Cost % total 1 Structure 874,772.94€ 19% 2 Preliminary Work 636,431.98€ 14% 3 Walls 242,052.97€ 5% 4 Impermeabilization and insulation 68,235.82€ 2% 5 Roof 28,908.36€ 1% 6 Floor covering 141,260.43€ 3% 7 Column and wall cladding 283,276.57€ 6% 8 Ceiling cladding 75,304.09€ 2% 9 Windows and steel structure 241,470.86€ 5% 10 Furniture and wood work 207,994.07€ 5% 11 Painting 75,970.01€ 2% 12 Sanitary wares and accessories 126,225.81€ 3% 13 Cleaning and handover preparation 26,440.65€ 1% 14 External areas finishing 24,654.34€ 1% 15 Hidraulic instalations 392,980.11€ 9% 16 Electrical instalations 509,256.24€ 11% 17 Mechanical instalations 40,521.64€ 1% 18 HVAC 518,189.98€ 11% Total: 4,513,946.87€ 100% Afterwards, it was defined how the project areas would be classified. The company had already used the “Rooms” tool in the Revit software to classify areas in its design process. However, they were using it for the purpose of showing the name of the room in the 2D floor plans generated by the software. In contrast, within this workflow, it will use the “Name” parameter on the room element as a connection between the BIM model and the cost historical database. The BIM model received contained several different classifications of rooms, depending on their use and location. However, the names of this classification had some specific factors, such as floors and gender of the toiles, generating 36 different room classification. The current Classification System was maintained as a basis, and the areas with the same use were grouped. After grouping, the project areas were separated into 12 items, namely: Bathroom, breakfast area, elevator, external area, hall, hotel room, kitchen, lobby, parking place, roof, staircase and technical area. The initial classifications and the final grouping are shown in table Figure 36. Figure 37 and Figure 38 figure shows in a floor plan how the areas were organized after classifying each room element. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 51 Figure 36 - Initial and final room classification Figure 37 - The floor plans -1, and 0. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 52 Figure 38 - The floor plans 1,2,3 (left) and roof (right) Once the cost classification system and the project areas were defined, it was necessary to organize the information according to the areas and to divide it between the systems. Although the cost spreadsheet provided already contains the total values separated by the systems, it was not classified by areas. Their total values were calculated based on the unit price of the activity multiplied by the total quantity of the entire project. Thus, it was necessary to segregate the total amount by the classified areas. At this stage, the importance and difference in the reuse and sharing data between projects elaborated applying the BIM methodology and elaborated in CAD-based solutions was remarkable. Some of the systems were developed based on the BIM methodology, and the designers delivered others in CAD form, and this directly impacted the way the information was worked on. For the systems within the BIM methodology, the quantity take-off item was extracted by “schedules” in Revit, itemizing all the instance on the schedule and determined the related area classification by visual verification on the model, as shown in Figure 39. Besides, the company provided some floor plains as a support material for the quantity take-off. With this task, it was possible to define the impact percentage of each system into each area. These percentages were applied to the total value of the systems and after divided by the floor plan area of corresponding, generating the necessary information for the workflow. For the systems developed on the CAD-based solution were not possible to extract information in such a way. The data contained on it was mainly designed applying lines and layers and was not possible to automatically extract any quantity-take off report. Due to it, the cost value of these systems was divided equally among the areas. Table 3 resumes the systems, methodologies applied in their development and the cost separation method. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 53 Figure 39 - Hotel Room’s windows selected in the schedule and highlighted on the floor plan Figure 40 shows all the cost values per room and systems, while Figure 41 shows the gathered values per room. Subsequently, the content of Figure 40 was automatically manipulated and organized in the same template needed by the workflow and linked to the estimation file. Considering all these tasks, the process of collect and organize the historical data was finished. The following step was to collect the layout information from project 2. Bathroom Breakfest Area Elevator External Area Hall Hotel Room Kitchen Lobby Parking Place Roof Staircase Technical Area Structure 252.56€ 252.56€ 252.56€ -€ 252.56€ 252.56€ 252.56€ 252.56€ 252.56€ -€ 252.56€ 252.56€ Preliminary Work 183.75€ 183.75€ 183.75€ -€ 183.75€ 183.75€ 183.75€ 183.75€ 183.75€ -€ 183.75€ 183.75€ Walls 59.04€ 68.97€ -€ -€ 105.65€ 71.24€ 133.11€ 122.06€ 29.03€ -€ 42.51€ 61.91€ Impermeabilization and insulation 66.07€ -€ 105.37€ -€ -€ -€ 136.25€ -€ 16.89€ 12.38€ -€ 63.31€ Roof -€ -€ -€ -€ -€ -€ -€ -€ -€ 34.97€ -€ -€ Floor covering 47.87€ 60.82€ -€ -€ 26.18€ 41.57€ 59.70€ 62.42€ 18.14€ -€ 81.70€ 18.05€ Column and wall cladding 152.36€ 26.61€ -€ -€ 10.65€ 112.78€ 85.37€ 29.13€ 9.60€ -€ 70.94€ 35.98€ Ceiling cladding 23.32€ 21.78€ -€ -€ 19.30€ 24.80€ 18.60€ 28.78€ 17.33€ -€ 9.32€ 13.33€ Windows and steel structure -€ 156.23€ 50.89€ -€ -€ 61.45€ 82.73€ 213.94€ 35.47€ 16.96€ 334.81€ 11.15€ Furniture and wood work 66.95€ 51.43€ -€ -€ 44.99€ 84.64€ 48.28€ 89.53€ 2.94€ -€ 7.67€ 11.03€ Painting 18.39€ 52.14€ 117.31€ -€ 20.87€ 18.89€ 37.92€ 28.53€ 9.40€ -€ 24.50€ 35.24€ Sanitary wares and accessories 305.56€ -€ -€ -€ -€ -€ -€ -€ -€ -€ -€ -€ Cleaning and handover preparation 7.63€ 7.63€ 7.63€ -€ 7.63€ 7.63€ 7.63€ 7.63€ 7.63€ -€ 7.63€ 7.63€ External areas finishing -€ -€ -€ 43.14€ -€ -€ -€ -€ -€ -€ -€ -€ Hidraulic instalations 113.46€ 113.46€ 113.46€ -€ 113.46€ 113.46€ 113.46€ 113.46€ 113.46€ -€ 113.46€ 113.46€ Electrical instalations 147.03€ 147.03€ 147.03€ -€ 147.03€ 147.03€ 147.03€ 147.03€ 147.03€ -€ 147.03€ 147.03€ Mechanical instalations -€ -€ 1,251.44€ -€ -€ -€ -€ -€ -€ -€ -€ -€ HVAC 149.61€ 149.61€ 149.61€ -€ 149.61€ 149.61€ 149.61€ 149.61€ 149.61€ -€ 149.61€ 149.61€ System Rooms Figure 40 - Final cost historical data according to each system and room. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 54 Rooms Region Project Standard Cost by m2 Bathroom Portugal Medium 1,593.60€ Breakfest Area Portugal Medium 1,292.02€ Elevator Portugal Medium 2,379.03€ External Area Portugal Medium 43.14€ Hall Portugal Medium 1,081.68€ Hotel Room Portugal Medium 1,269.41€ Kitchen Portugal Medium 1,455.99€ Lobby Portugal Medium 1,428.42€ Parking Place Portugal Medium 992.83€ Roof Portugal Medium 64.32€ Staircase Portugal Medium 1,425.47€ Technical Area Portugal Medium 1,104.04€ Figure 41 - Final cost historical data by room. Table 3 - Systems and its cost separation method. Systems Information received Cost separation method Structure BIM Model Equally divided Preliminary Work Only cost data Equally divided Walls BIM Model According to the quantities Impermeabilization and insulation BIM Model According to the quantities Roof BIM Model According to the quantities Floor covering BIM Model According to the quantities Column and wall cladding BIM Model According to the quantities Ceiling cladding BIM Model According to the quantities Windows and steel structure BIM Model According to the quantities Furniture and woodwork BIM Model According to the quantities Painting BIM Model According to the quantities Sanitary wares and accessories BIM Model According to the quantities Cleaning and handover preparation Only cost data Equally divided External areas finishing BIM Model According to the quantities Hidraulic instalations CAD-based Equally divided Electrical installations CAD-based Equally divided Mechanical installations CAD-based Equally divided HVAC CAD-based Equally divided BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 55 4.3. Generating project information for cost estimation. The layout information from Project 2 was developed using CAD-based software. The provided information was composed of the floor plans of each floor and some elevations. Considering that the work has been done within a BIM environment, this information was not complete and was necessary to adapt it. The design process for this case study followed almost all the steps described in Chapter 3. The difference is that in the case study utilized a CAD layout as a base for the design, while the hypothetical project was started from scratch in Revit. After setting up the template in Revit, the floor plans were separated into separate CAD files and imported into their respective pre-configured levels. After that, the external and internal walls of the building were modelled to work as the room-boundaries. At this time, the basic wall by Revit was selected as a basis for modelling, and several type walls were created according to the thickness specified in the project. This step is significant, as the workflow uses the internal areas of the walls as the basis for calculation, and thickness differences between the modelled and designed information would impact the final result of the cost estimate. In addition, room separators were used in places where there was no physical separation of areas. Figure 42 shows layouts in the CAD format and the BIM Model. Figure 42 - CAD layout and the BIM model floor plan. Once finished, the “rooms” feature was applied into all the spaces and filled with the correspondent room information by the classification mentioned above. The BIM software calculates automatically the total area related to each room. Lastly, were prepared the schedule and exported the information by the delimited text format and imported to the database containing the historical data. Table 4 shows the total areas according to each room calculate by the BIM software. The last step performed was to select the information regarding the location and the standard of the project on the database, which was Portugal and medium, respectively. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 56 Table 4 - Total areas exported from the BIM Software 4.4. Results Once the historical cost data and the floor plan areas were filled into the database, the software automatically calculates and generate the cost estimation desired presents the total cost estimation generated and its values divided by the classification system adopted. Figure 44 shows the final cost estimation value for the case study layout. Besides, the workflow generated the average cost per square meter of the project (Figure 43), which allows comparing this estimation with the market values cost estimation. The validation system developed on the Excel application confirmed that no issues related to filling the historical data or the data imported from the BIM software were found. Location Portugal Standard Medium Project floor plan area 3318.25 Avarage cost per m2 1,295.77€ Database considered in the estimation process Figure 43 - Data selected in the database and the average costs per square meter BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 57 Item Systems Estimated Cost 1 Structure 838,048.57€ 2 Preliminary Work 609,713.55€ 3 Walls 226,950.40€ 4 Impermeabilization and insulation 67,516.49€ 5 Roof 27,219.80€ 6 Floor covering 130,835.23€ 7 Column and wall cladding 259,360.61€ 8 Ceiling cladding 71,919.32€ 9 Windows and steel structure 216,338.83€ 10 Furniture and wood work 191,837.88€ 11 Painting 71,976.07€ 12 Sanitary wares and accessories 119,903.67€ 13 Cleaning and handover preparation 25,330.63€ 14 External areas finishing 46,140.54€ 15 Hidraulic instalations 376,482.17€ 16 Electrical instalations 487,876.85€ 17 Mechanical instalations 35,816.22€ 18 HVAC 496,435.53€ 19 n/a -€ Total cost estimation: 4,299,702.37€ Cost Estimation with historical Data Figure 44 - Total cost estimation generated by the workflow Even though was achieved the desired cost estimation, was also possible to demonstrate more useful information related to this cost estimation. Cost reports divided by floors (Figure 45), rooms (Figure 46) and correlating floor and rooms (Table 5) were generated. This information could support the decision making by the stakeholders related to which are the most impactful areas in a project in the case where reduce the project cost is needed. Figure 45 - Cost estimation divided by floors. BIM-based cost estimation at early stages based on historical data. Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 64 REFERENCES Agarwal, R., Chandrasekaran, S., Sridhar, M., 2016. Imagining construction’s digital future. Cap. Proj. Infrastruct. Agostinelli, S., Ruperto, F., Sferra, A.S., 2019. 4D Bim-Oriented Digital Project Construction Management for the Aec Industry. Build. Inf. Model. Des. Constr. Oper. III 1, 193–203. Ashworth, A., Perera, S., 2013. Cost Studies of Buildings, Cost Studies of Buildings, Fifth Edition. Routledge. Azhar, S., Khalfan, M., Maqsood, T., 2015. 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Erasmus Mundus Joint Master Degree Programme – ERASMUS+ European Master in Building Information Modelling BIM A+ 67 LIST OF ACRONYMS AND ABBREVIATIONS 2D 3D 4D 5D 6D 7D AECO API BIM CAD CE CSV e.g. FPA HVAC IFC IPD MEP MSc NBIMS OBDC PDF PhD RIBA TXT UAC UK VBA Two-dimension Three-dimension Four-dimension Five-dimension Six-dimension Seven-dimension Architecture engineering construction and operation Application programming interface Building information modelling Computer-aided design Cost estimation Comma-separated values exempli gratia Floor plan area Heating, ventilation, and air conditioning Industry foundation class Integrated project delivery Mechanical electrical and plumbing Master of science National building information modelling standard Open database connectivity Portable document format Doctor of Philosophy Royal Institute of British Architects Text Unitary area cost United Kingdom Visual basic for applications