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The E ec o Su ace Finishes on Rising Damp in O ien ed
S and Boa d
E ika K a och ílo á 1, Jiří Pa loka 1, Jiří Šlanho 1
1 B no Uni e si y o Technology, Facul y o Ci il Enginee ing, Ins i u e o
Technology, Mechaniza ion and Cons uc ion Managemen , Ve eří 331/95, 602 00
B no, Czech Republic
[email p o ec ed]
Abs ac . I is known ha o ien ed s and boa d (OSB) is p one o wa e abso p ion. This
cha ac e is ic o OSB is undesi able, i can ha e a nega i e impac on he physical and
mechanical p ope ies o he ma e ial and i can also make i p one o a ack om wood-
des oying insec s, o o mould. The esea ch ollows p e ious wo k o he au ho s ela ed o
op imisa ion o su ace inishes o OSB in o de o inc ease i s mois u e esis ance. The aim o
he esea ch is o compa e he ise o dampness in es specimens wi h di e en ypes o
coa ing, sp ay, p ime and wa e p oo ing unde p ede ined condi ions. The pape con ains a
de ini ion o he basic ma e ial, es specimens and es me hods, and co e s 8 di e en ypes o
su ace inish ma e ials selec ed o applica ion o he es specimens. The esul s include
g aphs showing ise o dampness in he es specimens o each day o obse a ion. The esul s
a e also discussed and in he conclusion he esul s a e e alua ed. The esul s o he
expe imen s con i m he assump ion ha he choice o su ace inish has a signi ican e ec on
slowing down he ise o dampness in OSB.
1. In oduc ion
OSB is a wood-based building ma e ial ha sees e y widesp ead use. This popula i y is ela ed o he
se e al ad an ages i o e s, such as i s high dimensional s abili y, i s a ailabili y in la ge sizes, and
he ac ha i can be used as a load-bea ing ma e ial. [1]. OSB is employed o he cladding o walls
and oo s, and can also be inco po a ed in loo o ceiling s uc u es. I is he mos equen ly used
ma e ial in s uc u al insula ed panels (SIPs), whe e panels clad wi h OSB a e used o he ounda ion
o buildings on ounda ion s ips ins ead o base conc e e [1].
One o he disad an ages o OSB is ha i is p one o wa e abso p ion. Du ing he cons uc ion
p ocess be o e he building shell is sealed, some imes he exposu e o OSB o wa e om p ecipi a ion
is una oidable [2, 3]. As a esul , i swells up, which impai s i s dimensional s abili y. This is a se ious
p oblem especially in he case o loo panels [3]. I a la ge amoun o ainwa e accumula es, he e is
a isk ha he wa e may ise in o e ical s uc u es.
The au ho s o he a icle ocus on he possibili y o inc easing he esis ance o OSB o wa e
abso p ion and ensu ing i s dimensional s abili y using a sui able su ace inish. The use o a su ace
inish has he po en ial o educe he swelling o he OSB. Fo example, he applica ion o a highly
elas ic polyu e hane coa ing [4], he ea men o he su ace o he OSB wi h sp ayed mel ed wax [3],
7 h Wo ld Mul idisciplina y Ea h Sciences Symposium (WMESS 2021)
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2
a coa ing wi h a UV-cu ed su ace inish [5] o he applica ion o a nano echnological compound [6]
ha e all p o ed success ul in he pas . One o he au ho s’ c i e ia o he selec ion o su ace inishes
o es ing was ha hei applica ion should be as easy as possible and no equi e p io mechanical
su ace ea men s such as g inding [5]. Fu he mo e, an e o was made o choose p oduc s which a e
eadily a ailable on he ma ke and ela i ely cheap [7].
The esea ch builds on p e ious wo k by he au ho s [7], wi hin which he esul s o applying he
selec ed su ace inishes we e es ed in e ms o he swelling up o OSBs a e hei placemen in wa e
[8], and also h ough he de e mina ion o hei esis ance o mois u e ia a cycling es [9]. In he
cu en a icle, he e ec o su ace inishes is e alua ed by measu ing he ise o dampness h ough
he OSB. Two al e na i e es me hods (one des uc i e, one non-des uc i e) we e designed in o de
o allow he p og ess o mois u e ising h ough he mois u e o be obse ed.
2. Ma e ials and me hods
2.1. OSB speci ica ion
OSB/4 was selec ed o he pu poses o his esea ch. I is classi ied in he ele an s anda d as
a hea y-du y load-bea ing boa d o use in humid condi ions [10]. The in es iga ed OSB ( hickness
15 mm) was a comme cial p oduc om one o he main dis ibu o s on he Czech ma ke . The
manu ac u e decla es he ollowing composi ion: 85-92 % absolu ely d y wood weigh (mainly
so wood o he pine and sp uce ype, ha dwood con en up o max. 30 %), 4-6 % wa e (wood
mois u e), 3-6 % PMDI glue in he su ace and co e laye s, ≤1 % pa a in wax emulsion. The
gua an eed cha ac e is ic bulk densi y o he boa ds is g ea e han 600 kg/m3.
2.2. Tes specimens
All specimens a e cu om 15 mm hick OSB panels om he same manu ac u e , wi h he same
p oduc ion ba ch numbe . Fo he des uc i e me hod, samples measu ing 15 x 200 mm we e used,
while 30 x 200 mm samples we e employed o he non-des uc i e me hod. The choice o sample size
was made wi h ega d o he echnical capabili ies o he selec ed measu ing ins umen s ( o example,
he spacing o he measu ing elec odes o he ex e nal mois u e me e ), and in he case o he
des uc i e es , he op ion o cu ing he samples wi h a hand saw was also aken in o accoun . As wi h
he de ec ion o swelling a e s o age in wa e , he samples we e i s condi ioned o a cons an weigh
a a mean ela i e humidi y o 65 % and a empe a u e o 21 °C [7, 8].
2.3. Speci ica ion o su ace inishes
8 ypes o su ace inish sui able o OSB we e selec ed o applica ion o OSB es specimens. Each o
hem is supposed o inc ease he esis ance o OSB agains he e ec s o mois u e. Su ace inishes
which a e eely a ailable on he ma ke we e selec ed. In he case o some o he selec ed su ace
inishes, he manu ac u e ´s ins uc ions equi ed hei applica ion in se e al laye s o in combina ion
wi h ano he p oduc . The selec ed inishes do no equi e any special ea men s o be applied o he
su ace o he OSB i sel , only he emo al o any impu i ies o g ease. Excep o he co k mix u e
in ended o sp aying, all inishes can be applied wi h a b ush. A lis o he su ace inishes used and
hei composi ions, including hei mo e de ailed speci ica ion, is shown in able below (Table 1).
2.4. Rising damp in OSB
The essence o his es is o de e mine how high he wa e ises in a es specimen s anding in a
con aine o wa e wi h a wa e le el o 10 mm abo e he bo om o he con aine . The con aine wi h
he es specimens is placed in he same oom and unde he same condi ions as in he p e ious s ep,
whe e he samples we e b ough o a cons an weigh . Two a ian s o hese es s we e designed:
des uc i e and non-des uc i e.
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Table 1. Speci ica ion o es ed su ace inishes.
Numbe o
composi ion
Speci ica ion o he composi ion o he su ace inish
Use
1
Silicone wa e p oo ing coa ing – 1 laye
Ex e io
2
One-componen polyme -based wa e p oo ing sc eed – 1 laye
Ex e io
3
Ac ylic copolyme wa e emulsion pene a ion p ime – 1 laye
Co k mix u e o applica ion by sp aying (o ganic mix u e o c ushed co k,
ac yla e emulsion in a wa e dispe sion, pigmen s and wa e ) – 2 laye s
Ex e io
4
Wood ea men lacque sui able o p ime s (composi ion: ac yla e, TiO2,
BaSO4, whi e spi i , Na-phospha e, wa e , conse a ion addi i e) – 2 laye s
Ex e io and
in e io
5
Ac yla e wood colou (composi ion: ac yla e, TiO2, Fe2O3, silica e, whi e
spi i , glycol, p ese a i es, wa e ) – 2 laye s
Ex e io and
in e io
6
P o ec i e wa e -based agen o end g ain wood (composi ion: a mix u e o 5-
chlo -2-me hyl-2H-iso hiazol-3-on and 2-me hyl-2H-iso hiazol-3-on (3:1), 1,2-
benziso hiazol-3(2H)-on) – 1 laye
Ex e io
7
Adhesi e b idge (one-componen sol en - ee coa ing, mix u e o ille s and
agg ega es in a wa e s y ene-ac yla e dispe sion) – 1 laye
Ex e io and
in e io
8
Polyu e hane-based wood s eng hening agen (composi ion: diphenylme han-
4,4´-diisocyana , ange o a omas hyd oca bons C9-C11, diphenylme han-2,4´-
diisocyana , hexame hylen-1,6-diisocyana homopolyme ) – 1 laye
Wood ea men lacque sui able o p ime s – 2 laye s
Ex e io and
in e io
2.5. The des uc i e es
The g a ime ic me hod was used o he des uc i e es . Fo his pu pose, a o al o 15 samples wi h
he gi en inish applied o hei whole su ace and one se o samples wi hou any su ace inish a e
p epa ed o each su ace inish. The samples a e placed in wa e wi h hei sho e edge downwa ds,
wi h he wa e le el eaching 10 mm o he o al heigh o he sample. Measu emen s a e aken o a
o al o 5 days. A 24-hou in e als, 3 samples a e aken ou o he wa e and placed in a p o ec i e
con aine o p e en he wa e om e apo a ing. Smalle pa s a e g adually cu om hem a e e y 10
mm o heigh . These a e weighed wi h an accu acy o 0.001 g immedia ely a e collec ion.
A e wa ds, hey a e d ied a a empe a u e o 105 °C o a cons an weigh [11] and e-weighed wi h an
accu acy o 0.001g. The mois u e con en o he successi ely cu o indi idual pa s o es specimen
H is gi en as a pe cen age by mass and is calcula ed acco ding o he ollowing o mula (Equa ion 1),
which is based on s anda d EN 322 [11]:
𝐻 =
[(
𝑚!− 𝑚"
)
/𝑚"
]
×100
(1)
whe e mH is he mass in g ams o he es specimen du ing he i s weighing a e sample collec ion
and mo is he mass in g ams a he las weighing a e d ying.
2.6. The non-des uc i e es
Each su ace inish is es ed on a se o 3 specimens ea ed wi h a su ace inish ac oss hei whole
su ace. A se o 3 specimens wi hou a su ace inish is also es ed. The specimens a e placed in wa e
in such a way ha he bo om pa o he specimen is imme sed in wa e up o a heigh o 10 mm. The
7 h Wo ld Mul idisciplina y Ea h Sciences Symposium (WMESS 2021)
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specimens a e aken ou o he wa e e e y 24 hou s. The % H2O is measu ed on bo h sides o he
specimen using an ex e nal mois u e me e a le els loca ed a an inc easing dis ance om he edge o
he specimen ha is imme sed in wa e : his dis ance inc eases by 10 mm pe measu emen .
Th oughou he measu emen s, ca e is aken o always place he elec odes in he same place
symme ically wi h espec o he cen e o he specimen. The measu ed pe cen ages e e o he
absolu e mois u e con en o wood, as he e a e no ex e nal hyg ome e s a ailable speci ically o
OSB. The measu ing ange o he ex e nal hyg ome e is 6 o 30 %: a mois u e con en anging om 6
o 12 % means a d y specimen, 13 o 19 % a e limi alues, and 20 o 30 % is a high mois u e con en .
These measu emen s a e epea ed o 5 consecu i e days.
3. Resul s and discussions
The EN 300 s anda d speci ies a mois u e con en equi emen o OSB in he ange o 2 o 12 % when
shipped om he manu ac u e [10]. I is gene ally ue o wood used in buildings ha he mois u e
con en should no exceed 20 %, while wood wi h a pe manen mois u e con en o up o 12 % does
no need o be u he p o ec ed agains a ack by bio ic pes s [12].
The manu ac u e o he in es iga ed OSB s a es a mois u e con en o 4-6 %. Based on his da a, i
can be assumed ha he pa s o a sample wi h a measu ed mois u e con en o ≤6 % lie a a heigh o
which he wa e in he es appa a us has no isen. In he case o alues abo e 20 %, we can speak
abou a high mois u e con en , which can also be seen om he di ision o he measu ing scale o he
ex e nal hyg ome e .
The OSB samples wi hou any su ace inish and he samples p o ided wi h 8 ypes o su ace
inish ac oss hei whole su ace we e subjec ed o a des uc i e es in which he heigh o he ising
damp was de e mined o 5 consecu i e days. A o al o 9 se s o 15 samples (3 samples o each day)
we e subjec ed o he es . The esul s ob ained wi h he a i hme ic mean we e plo ed in 5 g aphs
showing he dependence be ween he calcula ed mois u e con en and he heigh o he es ed OSB
ma e ial abo e he subme ged base o e ime, as shown in he ollowing igu es (Figu e 1 – Figu e 5).
Figu e 1. Resul s o des uc i e es ing – day 1
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Figu e 2. Resul s o des uc i e es ing – day 2
Figu e 3. Resul s o des uc i e es ing – day 3
Apa om he sp ayed co k mix u e – composi ion 3 (Table 1) and he adhesi e b idge –
composi ion 7 (Table 1), all su ace inishes we e able o keep he mois u e con en below he c i ical
limi o 20 % o he en i e 5 days o measu emen . Composi ion 3 had signi ican ly wo se esul s in
compa ison wi h hose om he p e ious s age o he esea ch when su ace inishes we e e alua ed
on he basis o swelling [7]. This is because he c ushed co k g ains con ained in he mix u e end o
soak up wa e hemsel es and i isn´ possible o de e mine he di e ence be ween he amoun o wa e
abso bed by he boa d and ha abso bed by he su ace inish, as he su ace inish wasn´ sepa a ed
om he OSB be o e he weighing o he indi idual pa s o he es specimens. Fo he same eason,
he e a e also luc ua ions in his composi ion a g ea e heigh s abo e he base o he specimen on he
hi d day o measu emen (Figu e 3). The inc eased mois u e con en which appea s he e is p obably
no con ained in he OSB bu only in he su ace inish. Composi ion 2 – one-componen
wa e p oo ing sc eed (Table 1) – also achie ed wo se esul s in compa ison wi h he p e ious s age o

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he esea ch, whe e i pe o med he bes [7]. As wi h he p e ious case (composi ion 7), he su ace
inish i sel has a endency o soak up wa e .
Figu e 4. Resul s o des uc i e es ing – day 4
Figu e 5. Resul s o des uc i e es ing – day 5
OSB specimens wi hou a su ace inish and specimens p o ided wi h 8 ypes o su ace inish
ac oss hei whole su ace we e subjec ed o a non-des uc i e es du ing which he upwa d
p og ession o ising damp was de e mined o 5 consecu i e days using an ex e nal hyg ome e . A
o al o 9 se s o 3 specimens we e subjec ed o he es and he mois u e con en was always measu ed
on bo h sides o he specimen. The esul s ob ained by a i hme ic mean we e plo ed in 5 g aphs
showing he dependence be ween he calcula ed % mois u e con en and he heigh o he OSB
ma e ial abo e he subme ged base o e ime, as shown in he ollowing igu es (Figu e 6 – Figu e
10).
7 h Wo ld Mul idisciplina y Ea h Sciences Symposium (WMESS 2021)
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Figu e 6. Resul s o non-des uc i e es ing – day 1
Figu e 7. Resul s o non-des uc i e es ing – day 2
The esul s ob ained wi h he ex e nal hyg ome e essen ially con i m he esul s ob ained wi h he
des uc i e es . Composi ion 7 – adhesi e b idge (Table 1) pe o med e en wo se in his case. Jus
like composi ion 3 ( he composi ion wi h he co k mix u e o applica ion ia sp aying), his su ace
inish has a endency o soak up wa e by i sel . Howe e , unlike sp ayed co k, he hickness o his
su ace inish a e applica ion is much smalle . This explains he di e ence in he measu ed alues, as
i bo h su ace inishes ha e a endency o soak up wa e , he samples wi h a su ace inish ha is
applied in a hicke laye mus logically exhibi a highe mois u e con en .
In he g aphs ob ained ia non-des uc i e es ing (Figu e 6 – Figu e 10), he e a e mo e ob ious
luc ua ions in mois u e con en along he heigh o he specimen. The anspo o wa e in he OSB
akes place i egula ly [13, 14], and he ex e nal hyg ome e is mo e sensi i e o his ac .
7 h Wo ld Mul idisciplina y Ea h Sciences Symposium (WMESS 2021)
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Figu e 8. Resul s o non-des uc i e es ing – day 3
Figu e 9. Resul s o non-des uc i e es ing – day 4
4. Conclusions
The esul s o he expe imen s con i med ha a sui ably selec ed su ace inish can slow he p og ess
o ising damp in OSB, and also ha i can p e en he accumula ion o a high mois u e con en in
OSB ha is di ec ly exposed o he e ec s o wa e o a leas 5 days. I was also disco e ed ha a e
5 days o exposu e o he di ec e ec s o wa e , he wa e le el in he OSB ises o a max. heigh o 80
mm, which is also ue o a boa d wi hou any su ace inish. On he o he hand, an unsui able su ace
inish could cause he wa e o ise e en highe hanks o i s use. Ne e heless, based on expe imen s
pe o med in he p e ious s age o he esea ch when he e ec s o su ace inishes we e assessed on
he basis o he swelling o OSB boa ds, i can be concluded ha in such a case, mos o he mois u e
is e ained by he su ace inish i sel and does no en e he OSB.
7 h Wo ld Mul idisciplina y Ea h Sciences Symposium (WMESS 2021)
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Figu e 10. Resul s o non-des uc i e es ing – day 5
In conclusion, i can be s a ed ha he esul s om he measu emen s aken using an ex e nal
hyg ome e co espond e y well wi h he esul s om he des uc i e es , and a e bo h easie and
as e o ob ain. Howe e , i should be no ed ha he measu emen s we e always aken on bo h sides
o he boa d.
Re e ences
[1] M. Mo ley, “Building wi h S uc u al Insula ed Panels (SIPs): S eng h and Ene gy E iciency
Th ough S uc u al Panel Cons uc ion,” The Taun on P ess, 2000.
[2] P. D. E ans, M. Meisne , D. Roge son, “Machined ape s educe he di e en ial edge swelling
o o ien ed s and boa d exposed o wa e ,” Composi es Pa B: Enginee ing, ol. 50, pp.
15–21, 2013.
[3] B. T. Lö e , P. D. E ans, “Sp ayable ho mel waxes as wa e epellen s o o ien ed s and
boa d,” In e na ional Wood P oduc s Jou nal, ol. 10(3), pp. 102–110, 2019.
[4] V. Schmid, O. Yildiz, “Highly elas ic polyu e hane coa ing wi h 2 o 3 mm hickness o
cons uc i e wood p o ec ion,” Bau echnik, ol. 91(1), pp. 15–22, 2014.
[5] P. D. E ans, I. Cullis, “E ec o sanding and coa ing wi h UV-cu ed inishes on he su ace
oughness, dimensional s abili y and i e esis ance o o ien ed s andboa d,” Holz als Roh -
und We ks o , ol. 66(3), pp. 191–199, 2008.
[6] G. I. Man anis, A. N. Papadopoulos, “Reducing he hickness swelling o wood based panels by
applying a nano echnology compound,” Eu opean Jou nal o Wood and Wood P oduc s,
ol. 68(2), pp. 237–239, 2010.
[7] E. K a och ilo a, J. Pa loka, J. Slanho , “Op imisa ion o su ace inishes o o ien ed s and
boa d in o de o inc ease i s mois u e esis ance,” IOP Con e ence Se ies: Ma e ials Science
and Enginee ing, ol. 603(3), 2019.
[8] EN 317: 1993, “Pa icleboa ds and ib eboa ds. De e mina ion o swelling in hickness a e
imme sion in wa e ”.
[9] EN 321: 2001, “Wood-based panels - De e mina ion o mois u e esis ance unde cyclic es
condi ions”.
[10] EN 300: 2006, “O ien ed S and Boa ds (OSB) - De ini ions, classi ica ion and speci ica ions”.
[11] EN 322: 1993, “Wood-based panels - De e mina ion o mois u e con en ”.
[12] M. Blaha, L. Buko ský, “P e ence a ods aňo ání lhkos i, second ed. ”, ERA g oup spol. s .