Featuring Plywood in Buildings - Engineered Wood Products ...

Face QualityPlywood can be ordered with face veneers to suit the application. Veneer quality A is a high qualityappearance grade suitable for clear finishing. Veneer quality S defines an appearance grade whichpermits natural characteristics such as knots as a decorative feature. Veneer quality B is anappearance grade suitable for high quality paint finishing. Veneer quality C is a non-appearancegrade with a sanded solid surface i.e. all open defects are filled. Finally veneer quality D can haveopen defects and would normally be used as a back veneer on a plywood panel. Thus for a clearfinished aesthetic application requiring one viewed surface AD grade plywood would be specified.Under similar circumstances if a painted finish is required then a minimum of BD grade is thespecification. A choice of timber species other than pine for outer veneers is also available.Quality GuaranteedFor guaranteed compliance andreliability specify that theplywood used must be brandedwith the appropriate EWPAAproduct certification stamp. Thisstamp certifies the product hasbeen manufactured under aformalised process based qualitycontrol program and is thereforefit for use as described in thisliterature.4

When you specify plywood be sure it has the PAA certification markThe EWPAA has been accredited by the Joint Accreditation System of Australia and New Zealand(JAS-ANZ), the peak accreditation body in both countries established by government treaty, as aproduct certification body for plywood and other glued structural veneer products. Plywoodcladding, lining and roofing manufactured under the EWPAA quality brand stamp assures productconformance to the relevant product standard.5

Curving PlywoodPlywood can be safely curved forapplications such as ceilings and featurewalls. Table one provides guidance forthe minimum recommended radii. Twofactors should be considered beforeselecting the plywood thickness. Firstly,the amount of force and hence theincreased fixings that are required to pulland hold the panel in tight radius;thicker panels require considerable forceparticularly in thickness above 12mm.secondly, with tighter radii the change ofradii between the ends of each sheet(which tend to be straighter) and thebalance of the panel becomes morevisually obvious. Therefore for tighterradii it is best to use thinner plywoodsand closer supports.Table 1 : Recommended minimum bendingradii for plywood liningsNormalThickness(mm)Along face(m)Across face(m)4.5 1.1 0.67 1.8 1.09 2.3 1.312 3.6 2.415 4.6 3.017 6.0 4.4Acoustics and Sound InsulationPlywood is an excellent reflector of sound, an acoustic property put to good use in applicationssuch as the internal lining of the Sydney Opera House. Alternatively, perforated plywood withsound insulation behind can act as a sound absorbing lining.The most important factor determining the ability of a wall system or lining to absorb transmittedsound is its mass per surface area. There is no such thing as an ultra-lightweight, high efficiencyacoustic partition. However a double-sided plywood partition reduces the level of noisetransmitted by around 35 decibels. To achieve higher levels with timber framing requires staggeredor double stud wall systems fitted with sound insulation. Another option is the inclusion of leadsheet in the wall system.7

Thermal PerformanceThe real advantage of lightweight timberconstruction in a subtropical or tropical climateis the ability to provide very liveable buildingswith wall systems having low thermal mass.Thus in the cool of the evening following a hotday the wall will cool rapidly and not keepheating the interior. Walls with high thermalmass hold substantially more heat thuscontinue to radiate heat in the evening.In cooler climates, or if the building is to be airconditioned, the addition of insulation to thetimber structure can provide equivalentthermal insulation to solid construction. Forexample the addition of R1.5 batts into aplywood clad with reflective sisalation on90mm studs will result in a wall with anaverage R exceeding 2.2 (see table 2).Therefore, in winter a lightweight timber canbe a very effective insulator and keep thewarmth inside the building.Table 2 : Thermal resistance of timber framed plywood clad wallsR Value (m 2 o c/WattThroughInsulationZoneThroughStudOutdoor air film 0.04 0.0412mm Plywood Cladding 0.08 0.0820mm reflective air gap 0.58R1.5 Insulation 1.5090mm Stud 0.626mm Plywood Lining 0.04 0.04Indoor Air film 0.12 0.12TOTAL R VALUE 2.36 0.90Note:As a non-reflective 20mm air gap has an R value of 0.15, an insulation wall system withoutsisalation would reduce the total r value from 2.36 to 1.93 in the above table.8

Lightweight panelsPlywood is strong enough to do the job but still light enough to be installed by one person,saving time and money. The density of pine plywood is around 590kg/m 3 , thus a 2400 x 1200 x12mm plywood panel weighs approximately 20kg. Hardwood plywood may be up to 40% moredense than pine plywood.Fire Hazard PropertiesThe Building Code of Australia (BCA) is a uniform set of technical provisions for the design andconstruction of buildings and other structures throughout Australia. The BCA includes a section onFire Resistance, and designers and builders must ensure that their constructions satisfy this section.There are 3 categories for plywood used in constructions :1. Floor Materials and Coverings2. Wall and Ceiling Linings3. Other materials.The following tables list the properties for each of these types. For more information, you candownload the “EWPAA Fire Resistance” fact sheet from the EWPAA Web Site.Floor Material And CoveringsSpecies Thickness CRFPine, Hoop – Araucaria cunninghamiiPine, Radiata – Pinus RadiataPine, Slash – Pinus Elliottii15mm or greater17mm or greater17mm or greaterBetween2.2 and 4.5Smoke DevelopmentRateLess than 750percent-minutes9

Wall and Ceiling LiningsPlywoodSpeciesMinimumThickness (mm)GroupNo.Average SpecificExtinction Area(m 2 /kg)Pine, Radiata – Pinus Radiata 6mm or greater 3 < 250Lauan – Shorea agsaboensis 6mm or greater 3 < 250Pine, Hoop 6mm or greater 3 82.4Pine, Slash 6mm or greater 3 96.0Other MaterialsFace Veneer CommonNameBotanical NameSpread of FlameIndex (0-10)SmokeDeveloped Index(0-10)Klinkii pine Aurancaria hunsteinii 8 4Radiata Pine Pinus radiata 8 2Radiata Pine (scorchedand brushed surface)Pinus radiata 7 2Energy Costs of ConstructionPlywood is manufactured from a natural, renewable resource; wood. The energy requirements forthe manufacture of plywood are relatively low when compared to most other competitive buildingproducts. A comparison of processing energy used to manufacture cladding materials is provided intable 3Table 3: Process energy for various claddingsCladding MaterialProcessing Energy(mJ/m 2 )19mm timber weatherboards 9012mm plywood 114150mm concrete blocks 3000.6mm galvanised steel sheet 308100mm bricks 100010

Plywood Exterior CladdingPreservative treated structural or exteriorplywood applied direct to studs as exteriorcladding can provide a cost efficient,modern architectural look for the mostbasic or elaborate building project.Significant costs savings are possible if thecladding is structural plywood as it can alsoact as bracing to protect the structure fromwind and earthquake forces. In addition tobracing the structure, structural plywoodcladding provides tie down of the top plateto the bottom plate against wind uplift-refer to the EWPAA “Structural Plywood Wall Bracing Manual” for details, available from theEWPAA Web Site. Additional cost saving can be made with structural plywood clad framing fromeliminating the need to use a ribbon top plate to strengthen the top plate for trusses or rafters thatdon’t coincide with the stud location.Durability RequirementsThe two most important characteristics forguaranteed long term performance ofplywood as exterior cladding are treatmentagainst fungal and insect attack, and thepanel be manufactured with permanentType A bonds. The preservation treatmentshould be a minimum of hazard level H3“outdoors above ground” as defined byAS/NZS1604.3. The preservative treatmentcurrently available are Ruply andAmmoniacial Copper QuaternaryCompounds (ACQ) , veneer treatmentsystems, and a number of pressuretreatments for finished panels, includingCopper Chrome Arsenate (CCA) and LightOrganic Solvent Preservatives (LOSP) .Structural plywood to AS/NZS2269 has a Type A bond, and exterior plywood to AS/NZS2271 can beordered with Type A bonds. For maximum cost effectiveness it is good practice to use structuralplywood as a wall bracing as well as cladding.For maximum long term performance to exposed face of the plywood cladding should be finishedwith a water repellent or a 100% acrylic latex paint system. Additionally, the edges of the plywoodpanel should be sealed to minimise water uptake in the end grain. The edge sealing can be doneusing a water repellent or the same primer used on the face, and is most readily applied while theplywood is in a pack, before installation. Some plywood cladding products presently available in themarketplace have a machined or textured face veneer which provides a good surface to hold paint,11

educes and disguises any surface checking of the face veneer effectively by dispersing or reflectingthe incidence of solar radiation.InstallationTypically, plywood claddingproducts are manufactured to suit1200mm cover with shiplapped orother machines joints, thus thestuds need to be at 600mm or400mm centres. These shiplapjoints allow for some panelmovement. If square edged panelsare used, leave a 2-3mm gapbetween joints on studs toaccommodate panel movement dueto moisture changes.The length of standard plywood cladding products available are 2440mm, 2700mm, 2745mm with3050mm sheets having limited availability. Other panel sizes are available subject to specialenquiry.Plywood claddings are normally installed vertically, but may also be placed horizontally (i.e. longdimension across the studs) if horizontal studs are nogged and detailed to prevent water ingressthrough the joints. Noggings are not required for vertical installation of plywood cladding, unless itis under a horizontal joint. The minimum plywood thickness for external cladding are given in table4 , and the minimum recommended fastener sizes are given in table 5.PlywoodStress GradeTable 4: Minimum plywood thickness (mm) for external claddingStud Spacing (mm)Plywood face grain running Plywood face grain runningverticallyhorizontally400/450 600 900 400/450 600 900F11 12 12 17 8 8 12F14 12 12 16 7 7 12Table 5: minimum recommended fastener sizesPlywood Thickness Up to 7mm Up to 21mmNails to timber 2.8mm dia x 40mm 2.8mm dia x 50mmScrews to timber No.8 x 30mm No.8 x 40mmScrews to steel No.10 x 45mm No.10 x 45mmNotes:1. Nails are flathead, and screws are self drilling countersunk head.2. Fasteners must be no-staining and corrosion protected. For some applications stainless steelor silicon bronze fasteners may be required.12

It is essential in plywood cladding installation that all joints are weatherproofed using shiplappedjoints, battened joints, caulking, flashing timber or elastomeric sealants. Shiplap joints are bestinstalled facing away from the prevailing weather. The use of sisalation or building paper isoptional, however, when butt or horizontal joints are utilised, or the framing is steel, the use of thisextra protection is recommended. Where used, sisalation must be of the vapour permeable type.To allow for movement in the panel due to excessive wetting during rainy periods, a 2-3mm gapmust be provided at all panel edges.Bracing Resistance ofPlywood Exterior CladdingPlywood cladding fixed to timberstud walls, in accordance with allof the requirements of theEWPAA “Structural Plywood WallBracing Manual” (available fromthe EWPAA Web Site) willprovide, depending on spacing’sand connection to the sub floor,from 3.0kN/m of bracingresistance per 900mm of cladwall length.13

Typical Joint Details for Plywood Exterior CladdingVertical Joint DetailsHorizontal Joint Details14

Corner Joint Details15

FinishingThe plywood surface must be protected to avoid mechanical breakdown (surface checking) andmaximise its appearance and durability. High quality oil based exterior wood stains or 100% acryliclatex paint systems are recommended. Always use a reputable paint brand as cheaper alternativesdo not always perform. Light colours are recommended in preference to darker colours as they givesuperior performance. In humid areas where mould may grow on the paint surface the use ofquality mouldicide in the paint is recommended.16

Plywood Interior Wall & Ceiling LiningPlywood with a high quality real wood face veneer can be clear finished to give a real timberappearance to walls, to ceilings or as an eaves lining on verandahs. The plywood face can betraditional rotary peeled or sliced veneer. Alternatively, the plywood can be V grooved thus provinga lining having a traditional planked effect to V jointed boards.Plywood SpecificationIf the lining is designed to have a secondaryas a bracing or a structural diaphragm theplywood must be structural plywood toAS/NZS2269. However, for non structurallining applications completely protected fromthe weather any plywood product withappropriate face veneer is acceptable. Theplywood must be manufactured to aminimum of AS/NZS2270.The appearance of decorative veneer variesconsiderably depending on species, timbersource and the method of veneering andplywood manufacturer. Most plywood liningin the marketplace has attractive rotarypeeled pine veneer faces; however, somesliced veneers are available and can bespecially matched for colour and figure. Theface veneers are sanded smooth ready forthe selected surface finish. The back side ofthe decorative plywood normally is nondecorativeand is of reduced quality.For ceilings, 9mm and 12mm plywood liningsare available with tongued and groovededges to negate the need for nogging underthe panel sides. If square edged panels areused framing is required to support all edges.Recommended minimum plywood thicknesses are given in table 6. Standard panel size is 2400mmx 1200mm. 2700mm x 1200mm panels are not as readily available.InstallationTo minimise shrinkage or expansion of panels after installation, it is good practice to let theplywood panels acclimatise to room temperature and humidity for several days before final fixing.This is best achieved by breaking open the packs and laying out the panels to allow air to circulatearound them.17

Wall linings may be fixed to the wall framing withstructural elastomeric adhesives and/or panelpins. Ceiling lining panels must be installed withthe face grain running across or at right angles tothe ceiling battens. For ceiling panels the nailsused normally have flat heads, or the screws havecountersunk heads, to avoid head pull through.Wood coloured putty can be used to stop fastenerholes if required. Alternatively, the use of siliconebronze, copper or copper coloured flathead nailsor countersunk screws can look very effective inclear finished timber.If the plywood lining is fixed to exterior masonry walls, battens are recommended and the masonrywall must be waterproofed. Waterproofing can be achieved by using a polythene vapour barrier.Plywood Thickness and Support Spacing’sTable 6: Recommended minimum plywood thickness and support spacing’sStud/support spacing (mm) Wall Lining Ceiling lining450 4mm 6mm600 6mm 6mm900 9mm1200 12mmNote: for ceiling lining the face grain must run across the span.18

Bracing Resistance of Plywood Wall LiningStructural plywood wall lining of a minimum 6mm thick F11 (including panels grooved at 100mmcentres), fixed to timber and stud walls in accordance with Table 7 can provide bracing resistanceagainst wind and earthquakes. The bullet head nails may be punched just below the plywoodsurface.Table 7: Limit State Bracing Resistance of Structural Plywood Wall Lining (6mm F11 minimum)Fixing DetailsNailed at 100mm centres around all edges and butt joints and at200mm on the intermediate studsGlued along all edges and intermediate supports with a continuous6mm bead of elastomeric adhesive and nailed at 200mm centresBracing Resistance2.1kN/m5.3kN/mNotes:1. Nails a minimum of 2.5mm diameter x 40mm bullet head.2. Studs spaced at a maximum of 600mm centres.3. Structural elastomeric adhesive that meets American Plywood Association Standard AFG-01.4. Bracing Resistance applies to panels a minimum of 900mm width and a maximum wall heightof 2700mm.5. Fixing of the bottom plate to the sub-floor can be nominal nailing for the 2.1 kN/m system butfor the 5.3kN/m system the fixing must be strapped or bolted at a minimum of 1200mmcentres as detailed in the EWPAA “Structural Plywood Wall Bracing Manual” which is availablefrom the EWPAA Web Site.FinishingHigh quality paints, stains, or clearfinishes are recommended for plywoodlinings. Tinted clear finishes e.g. liminggrey, allow decorators to create amodern coloured key timber décor.The use of high gloss finishes andpaints tend to highlight naturallyoccurring and manufacturingcharacteristics of plywood such aschanges in grain and beat marks fromthe sanding. Matt finishes and paintsare recommended to provide a naturaltimber finish.19

Lightweight Roofing SystemT&G structural plywood in combination with shingles or overlayed waterproof membranes canprovide a safe, lightweight, flat or curved roof system in residential, light commercial and industrialbuildings. Thickness/span details for a structural, non-trafficable plywood roof system to supportlightweight roofing are given in table 9. If the roof is to be trafficable, then the plywood must betreated as a floor and design data sourced from the EWPAA design manual “T&G StructuralPlywood for Residential Flooring” available from the EWPAA Web Site. The T&G plywood providesa structural diaphragm and eliminates the need for other forms of bracing in the roof system. Thedesign of plywood diaphragms is covered in Appendix J of AS/NZS1720.1 Timber Structure Code.Installation of Structural Plywood Roofing SystemPlywood SpecificationThe plywood to be used is CD or DD grade T&G structural plywood to AS/NZS2269. Specialised T&Gplywood with a decorative underside, usually V grooved to give a planked effect, can be used as acombined structural roof and decorative ceiling. Square edged plywood can be used but will requirenogging under the side joints.Roofing OverlayThe roofing overlay must be waterproof and durable. It may be decorated asphalt or fibreglassshingles, timber shakes or shingles, rubber, acrylic or bitumen membranes or metal tiles or decking.InstallationThe two major requirements for the T&G structural plywood are the face must run across i.e.perpendicular to, the rafters or trusses, and the plywood must be continuous over two or morespans. The plywood should be installed with 2-3mm gap at all sheet edges, the appropriate fixingsare given in Table 8, and the minimum plywood thickness relative to truss or rafter spacing arelisted in Table 9.20

Table 8: Fixing of T&G Structural Plywood to Non Trafficable RoofsDesign speed(permissibleStress)33 metres/second41 metres/secondNon CyclonicMinimum Fastener2.8mm dia. X 50mmFlathead NailsNo. 8 x 40mmCountersunk selfdrilling wood screws3.05mm dia. X 50mmFlathead NailsNo.8 x 40mmCountersunk selfdrilling wood screwsFastener Spacing at End and Intermediate Supports (mm)General roofs areasWithin 1200mm of RoofPerimeters150 100150 100100(for 1200mm spans)150(for 900mm & 800mm spans)50(for 1200mm spans)75( for 900 & 800mm spans)150 100Notes:1. The above fixings are applicable to timber species with joint strength J4 and JD4 and to plywood up to21mm in thickness.2. For higher wind speeds or cyclone sites fixings are to be designed for uplift in accordance withAS/NZS1170.2 “wind actions”.Table 9: Allowable structural plywood thickness and rafter spacing for plywood non-trafficableroofs supporting light weight roofing systems (20kg/m 2 max.)Rafter or TrussSpacing (mm)Minimum Allowable Plywood Thickness (mm)F8 F11 F14800 13 12 12900 16 15 151200 19 17 1621

Revision HistoryRevision Changes Date Who5 Fixed a minor error in the table of the curving plywood section 28-10-13 MB4 Updated logos and member list 07-02-12 MB Updated to include latest JAS-ANZ Logos3.0 Fixed missing fastener description for installation of exteriorcladding. Reformatted.2.0 Updated several pictures. Updated Fire resistance information1.0 Initial Release18-12-08 MB28-10-08 MB22

EWPAA MembersPlywood and Laminated Veneer Lumber (LVL)Member Name Location Phone Fax WebAusply NSW +61 2 6926 7300 +61 2 6922 7824 www.ausply.comAustral Plywoods Pty Ltd QLD +61 7 3426 8600 +61 7 3848 0646 www.australply.com.auBig River Group Pty Ltd NSW +61 2 6644 0900 +61 2 6643 3328 www.bigrivergroup.com.auCarter Holt Harvey Woodproducts Australia(Plywood) – MyrtlefordVIC +61 5751 9201 +61 3 5751 9296 www.chhwoodproducts.com.auCarter Holt Harvey Woodproducts Australia –Nangwarry LVLSA +61 8 8739 7011 www.chhwoodproducts.com.auCarter Holt Harvey Woodproducts - MarsdenPoint LVLNZ +64 9 432 8800 +64 9 432 8830 www.chhfuturebuild.co.nzCarter Holt Harvey Woodproducts (Plywood) -TokoroaNZ +64 7 885 5999 +64 7 885 5614 www.chhwoodproducts.co.nzFiji Forest Industries FIJI +67 9 881 1088 +67 9 881 3088IPL (West Coast) Ltd NZ +64 3 762 6759 +64 3 762 6789Juken New Zealand Ltd (Gisborne) NZ +64 6 869 1100 +64 6 869 1130 www.jnl.co.nzJuken New Zealand Ltd (Wairarapa) NZ +64 6 370 0650 +64 6 370 0653 www.jnl.co.nzNelson Pine Industries Ltd NZ +64 3 543 8800 +64 3 543 8890 www.nelsonpine.co.nzPNG Forest Products Ltd PNG +67 5 472 4944 +67 5 472 6017 www.pngfp.comRH (PNG) Ltd PNG +67 5 325 5600 +67 5 325 6165 www.rhpng.com.pgValebasoga Tropikboards Ltd FIJI +67 9 881 4286 +67 9 881 4154Wesbeam Pty Ltd WA +61 8 9306 0400 +61 8 9306 0444 www.wesbeam.comParticleboard and MDFMember Name Location Phone Fax WebAlpine MDF Industries Pty Ltd VIC +613 5721 3522 +61 3 5721 3588 www.alpinemdf.com.auBorg Panels Pty Ltd NSW + 61 2 6339 6111 + 61 2 6339 6220 www.borgs.com.auCarter Holt Harvey Woodproducts Australia NSW 1800 891 881 +61 2 9468 5793 www.chhwoodproducts.com.auD & R Henderson Pty Ltd NSW +612 4577 4033 +61 2 4577 4759 www.drhenderson.com.auLaminex VIC + 61 9848 4811 www.thelaminexgroup.com.auTasmanian Wood Panels (Aust) TAS +613 9460 7766 +61 3 9460 7268Weathertex Pty Ltd NSW 1800 040 080 www.weathertex.com.auVisit the EWPAA Website to get the latest information. www.ewp.asn.auVisit www.ewp.asn.au/register to ensure your products carry genuine EWPAA certification23