Fire protection ability of wood products

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Full text

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Fire protection ability of wood products

Birgit Östman, Rolf Hilling, Lars Boström

SP Report 2012:12

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Fire protection ability of wood products

Birgit Östman, Rolf Hilling, Lars Boström

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4 SP Technical Research Institute of Sweden Box 857, 501 15 Borås, Sweden (headquarters)

© 2014 SP Technical Research Institute of Sweden

SP Report 2012:12 ISSN 0284-5172

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Abstract

Wood products may protect underlying products from getting heated and ignited due to their low thermal conductivity and slow charring rate. A European system with K classes for the fire protection ability of coverings has been utilised for wood products. The classes are based on full scale furnace testing and the main parameters are the temperature behind the panel after different time intervals and the ability of the covering to protect underlying products. Three levels are defined: 10, 30 and 60 minutes. Wood-based panels and wood panelling and cladding may fulfil the European K classes for fire protection ability. The criteria for wood products are based mainly on panel thickness. A literature survey shows that similar fire protective behaviour of wood coverings has been verified by different methodologies in several countries in and outside Europe. Results from an extensive test program demonstrate that all K classes may be obtained for wood-based panels (particleboard, plywood, solid wood panels, OSB and hardboard) and for solid wood panelling and cladding. The thickness for achieving each class may vary slightly depending on wood product type and on mounting conditions and fixing device. The end-use applications of the wood products with K class are mainly as wall and ceiling coverings and for protection of underlying materials and structures. K classes are required by building regulations in some countries, e g Germany, Denmark and Sweden.

Key words:

fire protection, heat insulation, wood products, structural design, temperature rise

Sammanfattning (Swedish summary)

Det europeiska systemet med K-klasser definieras i klassifikationsstandarden EN 13501-2. Klasserna baseras på ugnsbrandprovning och de huvudsakliga parametrarna är temperaturen bakom skivan efter olika tider och skivans förmåga att skydda bakomliggande material. Tre nivåer har definierats: 10, 30 och 60 minuter.

Träbaserade skivor, träpanel och beklädnader kan uppfylla de europeiska K-klasserna för brandskyddande förmåga. Kriterierna för K-klassificering av träprodukter baseras huvudsakligen på skivans tjocklek.

En litteraturstudie visar att liknande brandskyddande effekt av träbaserade produkter har verifierats med olika metoder i flera länder inom och utom Europa.

Resultat från ett omfattande provningsprogram visar att alla K-klasserna kan uppnås för träbaserade skivor (spånskivor, plywood, massivträskivor, OSB och hård board) och för träpanel. Nödvändig produkttjocklek för att uppnå de olika K-klasserna varierar något för olika typer av träprodukter. Montering med spontade skarvar och fästdon har också viss inverkan.

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Preface

The test results reported have been obtained during a long time and within several national and European projects.

Public financial support from the European WoodWisdom-Net program and Vinnova Sweden’s Innovation Agency and industry financial support from the European initiative Building with wood (BWW) via CEI-Bois, the Swedish Forest Industries Federation and TMF Trä- och Möbelföretagen is kindly acknowledged. The Nordic companies Swedspan, Forestia, Vänerply and UPM have contributed both financially and by supplying some of the tested products. The research work has been carried out at SP Wood Technology and the fire testing at SP Fire Technology (now SP Fire Research). Special thanks to Rolf Hilling for excellent technical assistance and support.

The support, interest and involvement from all partners is kindly acknowledged.

The report has been finalized when the approval system according to the CWFT, Classification Without Further Testing, procedure within the European Commission has been completed by publication of the K classes for wood products in Official Journal in December 2014.

The classification may now be included in the relevant harmonized product standards and used for CE-marking.

Stockholm January 2015 Birgit Östman

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Content

Fire protection ability

8

Literature data

9

Conclusion on literature data 14

Fire testing and classification

15

Mounting and fixing 15

Furnace control 16

Measurements and observations 16

Fire classification criteria 17

CWFT – Classification without further testing 17

Wood products tested

18

Joints and fixing devices 18

Fire test results

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Analyses of fire test data

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K classes for wood products

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Final conclusions

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Fire protection ability

A European system with K classes for the fire protection ability of building panels has been introduced and is defined in EN 13501-2. The K classes are based on full scale furnace testing at horizontal orientation according to EN 14135, and the main parameters are the temperature behind the panel after different time intervals (10, 30 and 60 minutes) and the ability of the covering to protect underlying products. No collapse or falling parts is also required. The test principle is illustrated in Figure 1.

The aim with the K classes is to provide fire protection of underlying parts of a structure, e.g. the insulation in a wall or floor element. Two types of K classes are defined depending on the substrate behind. Class K1 10 includes substrates with density less than

300 kg/m3, while classes K2 10 - K2 60 includes all substrates, so in practise K2 classes

should be sufficient for wood-based products.

The K classes originate from the Nordic countries, where they have been used mainly for gypsum plasterboards, since the Nordic criteria also include reaction-to-fire requirements. However, in the European system, only the fire protection ability criteria prevail, so this is a great opportunity for wood products to demonstrate their fire protection abilities.

Figure 1. Principle for testing fire protection ability according to EN 14135. Table 1. European requirements for K classes according to EN 13501-2.

Class Test conditions Performance criteria Test

method Substrate behind covering Temperature rise behind, °C No collapse No damage on substrate Time min K1 10 Standard chipboard or substrate ≤ 300 kg/m3 < 250 x x 10 EN 14135 K2 10 Standard chipboard < 250 x x 10 EN 14135 K2 30 30 K2 60 60

Status reports with partial results have been presented at conferences e g /Östman 2010/. Partial results are also included in technical guidelines /Östman et al 2010 and 2012/.

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Literature data

Several studies have been performed that can be related to the K classes. A brief summary is presented here. Available test evidence is summarised in Figures 2-9 and in Table 2. Further information and data are given in the references.

Most of the previous work has been focused on developing methods to calculate the fire resistance of timber frame assemblies and to define the contribution from different assembly components such as panel and insulation products. The work has been

performed mainly in model scale furnaces of different sizes. The criteria for temperature increase behind the panel have usually been either 140 or 250 K, but this has been neglected in the present analysis, since the temperature increase at furnace testing is quite rapid at these temperatures and results in only about one minute difference.

Data from a study focussing on wood-based products /Norén and Östman, 1985/ are presented in Figure 2. It is obvious that panel thickness is an important factor for the contribution to fire resistance. This property is closely linked to the fire protection ability.

Figure 2. Effect of panel thickness on the contribution to fire resistance of different wood-based panels and gypsum boards /Norén and Östman, 1985/.

A similar study for solid wood panelling has been presented /Norén and Östman, 1986/, see Figure 3. Data on the contribution to fire resistance are given both at joints between the panelling and on panelling between joints, where longer times were observed.

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Figure 3. Contribution to fire resistance of solid wood panelling and cladding, both at joints and on panelling /Norén and Östman, 1986/.

Most of the previous work has been focused on developing methods to calculate the fire resistance of timber frame assemblies and to define the contribution from different assembly components such as panel and insulation products.

An overview of component additive methods for the calculation of the fire resistance of timber frame structures has been presented /König et al/ and data are summarised in Figure 4. For wood panels (=solid wood panelling and cladding in EN terminology), the low values at tongue and groove (t&g) have been adopted, which explains the difference to wood-based panels.

Figure 4. Basic values for the contribution to fire resistance of some materials used as panels /König et al/.

A similar approach is included in the fire part of Eurocode 5 /EN 1995-1-2/, for fire design of timber structures. The Eurocode approach is summarised below and illustrated in Figure 5. 0 5 10 15 20 25 0 5 10 15 20 25 30 Thickness, mm C ont ri but ion to fi re r e s is ta nc e , m in at joints on panelling

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Figure 5. Basic values for the contribution to fire resistance of some materials used as panels according to Eurocode 5 /EN 1995-1-2/.

New supporting data for the Eurocode 5 approach have recently been published /Schleifer and Frangi, Schleifer/.

In France, a different approach has been used to verify fire protection ability. Tests have been performed in a façade arrangement /Hognon/ and based on those, classes for 15 and 30 minutes fire protection have been regulated /Arrêté/. The French data are presented in Figure 6. It is interesting to observe how well these data correspond to the data on contribution to fire resistance of similar wood-based panels presented above.

0 10 20 30 40 50 0 10 20 30 40 Thickness, mm B asi c val u e, mi n Partilceboard and fibreboard Plywood

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Figure 6. French requirements on fire protection of wood-based panels /Hognon 1987/.

Two Japanese studies have been published /Harada et al, Kikuchi et al/, including data on the fire resistance of thick wood-based boards and the influence of board density, see Figure 7.

Figure 7. Japanese data on plywood (JCPW), particleboard (PB) and MDF /Harada et al/. 0 10 20 30 40 50 300 400 500 600 700 Minimum density, kg/m3 M in imu m th ickn ess, mm 15 minutes 30 minutes

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Some test data on particleboard and plywood /Hertel,2003 a and b/ are available from Germany, see Figure 8.

Figure 8. German data on particleboard and plywood /Hertel 2003a and b/. Danish tests /Dahlsgaard Jenssen and Drustrup, Danø and Drustrup/ have been

performed with the original Nordic methodology /NT Fire 003/ that is close to the European standard EN 14135. It is shown that 10 minutes protection is reached for 15 mm solid wood panelling. An evaluation report /Bluhme and Drustrup/ shows that the type of tongue and groove joints has minor importance.

In the US, thermal barriers are defined in a similar way as the European K classes and a NFPA standard is available /NFPA 275/. Research data for wood products are available /White 1982a and 1982b, White 2003/. Slightly shorter protection times were recorded for substrates made of foam plastic insulation.

The most recent data are from Austria /Teibinger and Matzinger/ and includes information on particleboard, hardboard and OSB, see Figure 9.

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Table 2. Summary of literature data.

Minimum thickness to reach criteria for 10 or 30 minutes protection, mm

Reference Wood-based panels Density < 400 kg/m3 Wood-based panels Density > 400 kg/m3 Solid wood panelling Density > 400 kg/m3 10 min 30 min WBP incl 10 min 30 min WBP incl 10 min 30 min 13 softboard 6-9 22-25 PB, PW, HB, MDF 8

Norén and Östman 1985 11/15

at joint

Norén and Östman 1986 11 32 PW 9 28 PB, PW, FB 18 at joint König et al 10 32 PW 9 27 PB, PW, FB 20 at joint EN 1995-1-2 30 general Lignum 30 PB, PW, MDF Harada et al < 13 PB, PW Hertel 2003a < 24 PB, PW Hertel 2003b

15 Danø and Drustrup

14/15 Dalsgaard-Jensen

and Drustrup

< 10 PB, PW, OSB Teibinger and

Matzinger 15 PW, PB, HB 15 White 1982a 11 PW White 1982b 29 PW, OSB, LVL White 2003 13 31 Kikuchi and Komazawa WBP = wood-based panels; PW = plywood; PB = particleboard; HB = hardboard; FB = fiberboard; MDF = medium density fiberboard; OSB = oriented strand board; LVL = laminated veneer lumber.

Conclusion on literature data

The literature data are summarized in Table 2. It is obvious that panel thickness is the most important factor for the contribution to fire resistance for wood-based panels. Density has a minor effect.

Similar thickness of the wood products to reach 10 and 30 minutes fire protection has been demonstrated. These data are promising for reaching European K class, but the methodologies used have been different, so further testing according to the European standards is needed to reach the European K classes.

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Fire testing and classification

The wood products have been tested in a horizontal furnace according to EN 14135 Coverings - Determination of fire protection ability.

Different thicknesses of covering, design and geometry for joints and fixing methods of the products are included. At each test, two full size specimen 3,0 x 2,4 m were included, since the furnace size is 5 m x 3 m. A series of pretesting with smaller elements 1,0 x 2,4 m was also performed.

Mounting and fixing

All products were mounted on the substrate prescribed in EN 14135, 19 mm particleboard 680 kg/m3, without any air gap or cavity behind.

The coverings were fixed to the substrate in the same way as in practise, i.e. with screws for all wood-based panels except hardboards/medium board where brads were used, and with nails for solid wood panelling and cladding.

All elements consisted of segments of the tested covering with joints according to EN 14135. The supporting system consisted of a framework of wooden beams with cc 600 mm and the particleboard substrate was mounted on the lower side of the framework. Further details on the mounting and fixing are given in chapter Wood products tested and in the test reports specified in Tables 5 and 6.

Typical design of test elements and instrumentation of full size specimen is given in Figure 10 a. Design of the elements for pretesting is given in Figure 10 b.

Figure 10 a. Typical design of segments in a full size tested covering 3,0 x 2,4 m with joints according to EN 14135.

Thermocouples behind the tested cladding are included to the left and typical screw spacing to the right (screw size and edge distance not to scale).

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Figure 10 b. Pretest element with six different specimen 1,0 x 2,4 m tested at the same time. Joints were included and three thermocouples were used for each specimen.

Furnace control

The furnace was controlled in accordance with EN 1363-1. The furnace temperature was measured with 5 plate thermometers and the measuring junctions were positioned approximately 100 mm below the fire exposed surface at the commencement of the test. The average temperature and the temperature of each plate thermometers were recorded and reported in the test reports.

The pressure in the furnace in relation to the ambient pressure in the test hall was measured and controlled 100 mm below the fire exposed surface of the test specimen. The furnace was controlled to an overpressure of approximately 20 Pa.

Measurements and observations

The temperature rise on the lower side of the particleboard substrate was measured with 8-9 thermocouples for the full size elements and recorded. Photographs were taken before and after the test.

After the test, the tested covering was inspected for collapse and the particleboard substrate for damage/charring.

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Fire classification criteria

There are two types of K classes defined in EN 13501-2 depending on the substrate behind. Class K1 10 includes substrates with density less than 300 kg/m

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, while classes K2

10 - K2 60 includes all substrates, so in practise K2 classes should be sufficient for

wood-based products.

The classification criteria for the K classes are defined in EN 13501-2.

A covering designated K2 is considered to give the prescribed protection for materials

behind the covering if during a test in accordance with EN 14135 within the classification period (10 min, 30 min or 60 min) there is no collapse of the covering or parts of it and also if the following requirements are fulfilled.

For a covering without a cavity or cavities behind it

 during the test the mean temperature measured on the lower side of the substrate shall not exceed the initial temperature by more than 250 °C and the maximum temperature measured at any point of this side shall not exceed the initial temperature by more than 270 °C, and

 after the test there shall be no damage or charred material at any point of the substrate.

CWFT – Classification without further testing

The classification of the fire protection ability of the wood products tested has been performed according to the CWFT - Classification without further testing procedure. This procedure may be used for products which have been proven to be stable in a given European class (on the basis of testing to the appropriate EN test methods within the scope of their variability in manufacturing allowed by the product specification

(harmonised standard or ETA European Technical Approval)). CWFT is a list of generic products, not a list of proprietary products.

The CWFT procedure is described in a document from DG Enterprise /CONSTRUCT 01/491 rev 3, 2004/. Products claiming CWFT must be clearly above the lower class limits, to provide a safety margin. The European Standing Committee on Construction, SCC, makes the final decision based upon the recommendations from the European Group of Fire experts, EGF. The advice of the EGF will largely determine whether the request is forwarded to the SCC for opinion.

Wood products are good examples of products having a stable fire performance. The CWFT approach has earlier been applied for the reaction to fire performance of several wood products. Results have been published e g /Östman and Mikkola 2006/. This is the first CWFT case dealing with fire protection ability performance.

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Wood products tested

Different types of wood products according to the harmonised standards EN 13986 and EN 14915 have been tested, five types of wood-based panels (plywood, particleboard, oriented strand board (OSB), hardboard/medium board and solid wood panels (SWP)) and solid wood panelling and cladding (SWPC), see Table 3.

The relevant product standards referred to are EN 300 Oriented Strand Boards (OSB) EN 312 Particleboards — Specifications

EN 622-2 Fibreboards - Specifications - Part 2: Requirements for hardboards EN 622-3 Fibreboards - Specifications - Part 3: Requirements for medium boards EN 636 Plywood — Specifications

EN 13353 Solid wood panels (SWP) – Requirements (multi layer products)

EN 14519 Solid wood panelling and cladding (SWPC) – softwood machined profiles with tongue and groove

EN 14951 Solid hardwood panelling and cladding (SWPC) – Machined profiles elements

Table 3. Wood products tested

Wood product EN harmonized product standard Thickness mm Fixing device (nail, screw etc)

Joints

Particleboard EN 13986 10, 12, 22, 25 screw square edges, t&g

Plywood EN 13986 9, 12, 24 screw square edges, t&g

Hardboard EN 13986 9 brad square edges

OSB EN 13986 10, 12, 25, 30 screw square edges, t&g

SWP EN 13986 13, 26, 52 screw square edges, t&g

SWPC EN 14915 15, 27 nail tongue & groove

Joints and fixing devices

The joints within a wood element were either with straight square edges or with tongue and groove profiles without gaps. Typical design is given in Figure 11. The thickness at the joints was the same as for the wood product.

Figure 11. Typical design of joints with square edges (to the left) or with tongue and groove (to the right).

The fixing devices were chosen according to industry guidance /Guide on screws and nails/ and producers´ recommendations, see Table 4. The edge distance was 3d (nominal diameter) for wood-based panels and 5d for SWPC.

Table 4. Fixing devices used for wood products

Fixing device Length/diameter(d), mm Spacing at edge, mm Used for Screw 25/2,5; 30/3.5; 30/3,9; 30/4,2; 41/4,2; 50/3,5; 57/4,2; 75/4,1 200 Particleboard, OSB, plywood, SWP Brad 40/1,7 100 Hardboard Nail 50/2,0; 50/3,5; 60/2,3 600 SWPC

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Fire test results

Typical examples of pictures from the fire testing according to EN 14135 are given in Figure 12.

Figure 12. Example from testing solid wood panelling. Above the exposed side of test sample before and after fire testing. Below to the left: The substrate behind the test sample after the fire testing.

Below to the right: Measured temperatures behind the test sample.

The pretest results with smaller specimen 1,0 x 2,4 m are summarized in Table 5 and illustrated Figure 13. They were considered to be promising, so standard testing with full size elements started.

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Table 5. Pretesting according to EN 14135 with smaller elements (1,0 x 2,4 m)

Test nr Product Thick -ness mm Density kg/m3 Joints t&g

Fixing device (nail, screw etc), mm End tim e min Max temp rise at end time C Time to Δ temp > 250 K min Char at substr ate Pass SP Test Repor t * Type Lengt h Ø Spacing at edge in field 1

Particleboard 10 ca 600 x screw 30 3,9 200 300 10 112 - No Yes

A -“- 10 ca 600 - -“- 30 3,9 200 300 10 112 - No Yes Particleboard 12 ca 600 x -“- 30 3,9 200 300 10 81 - No Yes -“- 12 ca 600 - -“- 30 3,9 200 300 10 90 - No Yes OSB 10 ca 600 - -“- 30 3,9 200 300 10 158 - No Yes -“- 12 ca 600 x -“- 30 3,9 200 300 10 132 - No Yes 2

Plywood 12 ca 400 - screw 30 3,9 200 300 10 121 - No Yes

B -“- 12 ca 400 - -“- 30 3,9 200 300 10 128 - No Yes Plywood 9 ca 400 - -“- 30 3,9 200 300 10 194 - Yes No Hardboard 9 ca 700 - -“- 30 3,9 200 300 10 125 - No Yes SWPC 15 ca 400 x nail 60 2,3 600 - 10 90 - No Yes -“- 15 ca 400 - -“- 60 2,3 600 - 10 88 - No Yes 3a

Particleboard 22 611 - screw 57 4,2 200 300 30 >250 26,5 Yes No

C Particleboard 2 x 12 592 - -“- 57 4,2 200 300 30 >250 22,8 Yes No Plywood 24 653 - -“- 57 4,2 200 300 30 176 - Yes No Plywood 2 x 12 699 - -“- 57 4,2 200 300 30 >250 20,7 Yes No OSB 25 615 - -“- 57 4,2 200 300 30 >250 29,5 Yes No SWP 27 454 x nail 60 2,3 600 - 30 98 - Yes No 3 b

Plywood 24 487 x screw 41 4,2 200 300 30 172 - Yes No

H OSB 25 611 x -“- 41 4,2 200 300 30 >250 28 Yes No Particleboard 22 735 x -“- 41 4,2 200 150 30 >250 27 Yes No Plywood 2 x 12 509 x -“- 41 4,2 200 150 30 >250 26 Yes No Particleboard 2 x 12 643 x/- -“- 41 4,2 200 150 30 >250 25 Yes No SWPC 27 434 x nail 60 2,3 600 - 30 119 - No Yes

OSB = Oriented Strand Board

SWPC = Solid wood panelling and cladding, planed tongue and groove with equal thickness */Hilling and Boström/

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Table 6. Standard testing (3,0 x 2,4 m elements) according to EN 14135

Tes t nr Product Thick-ness mm Density kg/m3 Joint t&g

Fixing device (nail, screw etc), mm End

time min Max temp rise at end time C Time to Δ temp > 250 K min Char at subst Pas s SP Test repor t *

Type Length Ø at Spacing edge field in

4b Particleboard 10 629 - screw 30 3,9 200 300 10 148 - Yes No E

4c Particleboard 10 652 x -“- 30 3,9 200 150 10 109 - No Yes G1

4c Particleboard 12 583 - -“- 30 3,9 200 300 10 92 - No Yes G2

5 Hardboard 9 771 - brad 40 1,7 100 200 10 157 - No Yes F1

6 OSB 10 590 - screw 30 4,2 200 300 10 178 - No Yes I1

4a Plywood 12 531 - -“- 30 3,9 200 300 10 120 - No Yes D

4d Plywood 12 477 - 2 screws 30 3,9 200 300 10 129 - No Yes L1

4d SWP 13 466 - -“- 30 3,9 200 300 10 107 - No Yes L2 5 SWPC 15 625 - nail 60 2,3 200 - 10 90 - Yes No F2 rev1 6 SWPC 15 457 x -“- 60 2,3 600 - 10 98 - No Yes I2 7 Particleboard 22 616 - 2 screws 50 3,5 200 300 30 573 29/ Yes No N1 10 Particleboard 22 683 - -“- 50 3,5 200 300 30 280 29 Yes No R1 12 Particleboard 25 660 x 2 screws 50 3,5 200 300 30 114 >30 No Yes T1 12 Particleboard 2x15 620 x -“- 25 2,5 200 300 30 788 26 Yes No T2 9 OSB 25 553 x 2 screws 41 4,2 200 300 30 208 >30 Yes No K2 9a OSB 25 609 x -“- 50 3,5 200 300 30 172 >30 Yes No O2 10 OSB 30 600 - -“- 50 3,5 200 300 30 96 >30 No Yes R2 rev1 8 Plywood 24 467 x -“- 50 3,5 200 300 30 482 >30 Yes No M2 8 Plywood 2 x 12 467 - 2 screws 25 2,5 200 300 30 820 19 Yes No M1 9a Plywood 24 467 x -“- 50 3,5 200 300 30 230 >30 No Yes O1 7 SWP 26 447 x -“- 50 3,5 200 300 30 115 >30 No Yes N2

9 SWPC 27 454 x nail 60 2,3 600 - 30 114 >30 No Yes K1 rev1

13 Plywood 2 x 24 465 x -“- 50 3,5 200 300 60 900 48 Yes No S2 14 Plywood 2 x 27 477 x -“- 50 3,5 200 300 60 851 56 Yes No U2 11 SWP 52 492 - 2 screws 75 4,1 200 300 60 102 >60 Yes No P2 rev1 14 SWP 53 443 at unexp -“- 75 4,1 200 300 60 101 >60 Yes No U1 15 SWP 52 443 x -“- 75 4,1 200 300 60 102 >60 Yes No V1 15 SWP 52 443 at unexp -“- 75 4,1 200 300 60 95 >60 No Yes V2 rev1 13 SWP 2 x 26 472 - 2 screws 50 3,5 200 300 60 226 >60 Yes No S1 11 SWPC 2 x 27 454 x nail 50 2,0 600 - 60 96 >60 No Yes P1 rev1

OSB = Oriented Strand Board SWP = Solid wood panels, multi layer

SWPC = Solid wood panelling and cladding, planed tongue and groove with equal thickness */Hilling et al/

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Analyses of fire test data

The fire test results have been analysed in terms of panel thickness, type of wood product, joints and char at substrate. The results are illustrated in figures 14-16.

Most tested products with no char at substrate also passed the temperature rise criterion on < 250oC at substrate. But some of the products passing the temperature criterion had some char at the substrate behind the covering. This may be caused by heat exposure at joints or fixing devices. However, no difference between straight and t&g joints could be observed, see lower diagram in figure 14.

The conclusion is that the combination of requirements on maximum temperature on substrate and lack of charring is useful as test criteria.

Figure 14. Full scale test results. Above for wood products with no char at substrate behind the covering and below for products with char at substrate.

No char at substrate

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Figure 15. Protection time according to EN 14135 for wood-based panels and solid wood panelling with different thickness.

The protection time for wood-based panels with different thickness is illustrated in Figure 15. The dependence on panel thickness is clear. The real protection time is longer, but not recorded, since the tests had to be terminated at the exact end times according to EN 14135 in order to be able to observe possible charring at the substrate.

The pretesting and the full size data have also been compared, see Figure 16. It is obvious that the results are quite similar, especially at 10 minutes fire exposure for which most of the tests were performed.

Figure 16. Comparison of testing wood products in model scale and full scale according to EN 14135. To the left for 10 minutes fire exposure and to the right for 30 minutes.

Protection time, min

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K classes for wood products

K class has been verified for fifteen wood products according to the CWFT procedure. Detailed documentation was supplied to the European Commission services /CWFT case report for K classes/. The documentation was carefully checked in several steps and at different levels and finally approved by SCC, the European Standing Committee on Construction.

In all cases the criteria according to EN 13501-2 were fulfilled:

 The maximum temperature rise behind the covering was less than 250 o

C

 There was no char on the substrate behind the covering

The safety margin to the class limit is generally very large and in average < 100 oC.

Table 7. Classification of wood products based on test results according to EN 14135

Product Thick-ness mm Density kg/m3

Joint Fixing device (nail,

screw etc) Max temp rise at end time C Char at substr ate Class EN 13501-2 SP Report part no * Type Min length mm Max spacing mm

Plywood 12 531 square edges screws 30 200 120 No K2 10a D

Plywood 12 477 square edges screws 30 200 129 No K2 10a L1

Hardboard 9 771 square edges brads 40 100 157 No K2 10a F1

Particleboard 10 652 tongue & groove screws 30 150 109 No K2 10

a G1

Particleboard 12 583 square edges screws 30 200 92 No K2 10a G2

OSB 10 590 square edges screws 30 200 178 No K2 10a I1

SWP 13 466 square edges screws 30 200 107 No K2 10a L2

SWPC 15 457 tongue & groove nails 60 600 98 No K2 10a I2rev1

Plywood 24 467 tongue & groove screws 50 200 230 No K2 30 O1

Particleboard 25 660 tongue & groove screws 50 200 114 No K2 30 T1

OSB 30 600 t&g at short sides only screws 50 200 96 No K2 30 R2

SWP 26 447 tongue & groove screws 50 200 115 No K2 30 N2rev1

SWPC 27 454 tongue & groove nails 60 600 114 No K2 30 K1rev1

SWP 52 443 tongue & groove screws 75 200 95 No K2 60 V2rev1

SWPC 2x27 454 tongue & groove nails (in each 50 layer)

600 96 No K2 60 P1rev1

a Fulfils also K

110 for substrates ≥ 300 kg/m3

* Parts of SP Test Report P905327 /Hilling et al/

OSB = Oriented Strand Board SWP = Solid wood panels, multi layer

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Table 8. Table in Commission Decision /Official Journal/

CLASSES OF FIRE PROTECTION ABILITY PERFORMANCE FOR WOOD-BASED PANELS and SOLID WOOD PANELLING AND CLADDING FOR WALL AND CEILING COVERING

Product 1) EN product

standard

Product detail 2) Minimum

mean density (kg/m3) Minimum thickness (mm) K Class 3)

Hardboard EN 13986 With and without

tongue and groove 5) 800 9 K2 10

4)

OSB EN 13986 With and without

tongue and groove 6) 600 10 K2 10

4)

Particleboard EN 13986 With tongue and

groove 7) 600 10 K2 10

4)

Particleboard EN 13986 With and without

tongue and groove 6) 600 12 K2 10

4)

Plywood EN 13986 With and without

tongue and groove 6) 450 12 K2 10

4)

Solid wood

panels EN 13986

With and without

tongue and groove 6) 450 12 K2 10

4)

Particleboard EN 13986 With tongue and

groove 8) 600 25 K2 30

OSB EN 13986 With tongue and

groove 8) 600 30 K2 30

Plywood EN 13986 With tongue and

groove 8) 450 24 K2 30

Solid wood

panels EN 13986

With tongue and

groove 8) 450 26 K2 30

Solid wood

panels EN 13986

With tongue and

groove 9) 450 52 K2 60

Solid wood panelling and cladding

EN 14915 With tongue and

groove 10) 450 15 K2 10

4)

Solid wood panelling and cladding

EN 14915 With tongue and

groove 10) 450 27 K2 30

Solid wood panelling and cladding

EN 14915 With tongue and

groove 11) 450 2 x 27

12)

K2 60

1) Mounted directly on any substrate without an air gap

2) Joints with square edges or tongue and groove profile and with the same thickness as the wood product and without gaps

3) Class as set out in Decision 2000/367/EC 4) K1 10 for substrates ≥ 300 kg/m3

5) Brad length minimum 40 mm and spacing maximum 100 mm 6) Screw length minimum 30 mm and spacing maximum 200 mm 7) Screw length minimum 30 mm and spacing maximum 150 mm 8) Screw length minimum 50 mm and spacing maximum 200 mm 9) Screw length minimum 75 mm and spacing maximum 200 mm 10) Nail length minimum 60 mm and spacing maximum 600 mm

11) Nail length minimum 50 mm (in each layer) and spacing maximum 600 mm

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26

Final conclusions

Main product parameters influencing the fire protection ability of wood-based panels and solid wood panelling and cladding are thickness and density. The joints and the fixings to the substrate are also important.

Wood-based panels of types plywood, particleboard, OSB and solid wood panels (according to EN 13986) with thickness at least 10 mm and hardboard/medium board with thickness at least 9 mm fulfil classes K1 10 (for substrates ≥ 300 kg/m

3

) and K2 10.

Wood-based panels of types plywood, particleboard, OSB and solid wood panels with thickness at least 24-30 mm fulfil class K2 30. Solid wood panels with thickness at least

52 mm fulfil class K2 60.

Solid wood panelling and cladding (according to EN 14915) planed with tongue and groove and with equal thickness at least 15 mm fulfil classes K1 10 (for substrates ≥ 300

kg/m3) and K2 10. Solid wood panelling and cladding of least 27 mm fulfil class K2 30

and of at least 2 x 27 mm class K2 60.

The classification has been approved by the European CWFT procedure and published in December 2014 /Official Journal /.

Wood based products fulfilling the different K classes are summarised in Table 9. These results may be included in the relevant harmonised product standards and used for CE-marking.

The end-use applications of the wood products tested are mainly as wall and ceiling coverings.

Table 9. Wood based products fulfilling K classes for fire protection ability.

K class

Product EN

standard

Joints Fixing device Min.

density kg/m3 Min. thickness mm Type Min length mm Max spacing at edge mm K210 a Particleboard EN 13986 Tounge

& groove screw 30 150 600 10

-“- EN 13986 - screw 30 200 600 12

Plywood EN 13986 - screw 30 200 450 12

OSB EN 13986 - screw 30 200 600 10

Hard board EN 13986 - brad 40 100 800 9

Solid wood panel EN 13986 - screw 30 200 450 13

Solid wood panelling and

cladding EN 14915

Tounge

& groove nail 60 600 450 15

K230

Particleboard EN 13986 -“- screw 50 200 600 25

Plywood EN 13986 -“- screw 50 200 450 24

OSB EN 13986 -“- screw 50 200 600 30

Solid wood panel EN 13986 -“- screw 50 200 450 26

Solid wood panelling and

cladding EN 14915 -“- nail 60 600 450 27

K260

Solid wood panel EN 13986 -“- screw 75 200 450 52

Solid wood panelling and

cladding EN 14915 -“- nail 60 in each layer 600 450 2 x 27 a

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27

References

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Classification of products of known and stable performance - Procedural aspects. CONSTRUCT 01/491 rev 3, 2004.

CWFT case report for K Classes, CWFT doc 174 rev 4, 2012 and Amendment, 2013.

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SP Technical Research Institute of Sweden

Our work is concentrated on innovation and the development of value-adding technology. Using Sweden's most extensive and advanced resources for technical evaluation, measurement technology, research and development, we make an important contribution to the competitiveness and sustainable development of industry. Research is carried out in close conjunction with universities and institutes of technology, to the benefit of a customer base of about 10000 organisations, ranging from start-up companies developing new technologies or new ideas to international groups.

SP Technical Research Institute of Sweden

Our work is concentrated on innovation and the development of value-adding technology. Using Sweden's most extensive and advanced resources for technical evaluation, measurement technology, research and development, we make an important contribution to the competitiveness and sustainable development of industry. Research is carried out in close conjunction with universities and institutes of technology, to the benefit of a customer base of about 9000 organisations, ranging from start-up companies developing new technologies or new ideas to international groups.

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