Plywood Structural Manual
Plywood Structural Manual
Plywood Structural Manual
March 2009
A
Woodproducts New Zealand
Contents
1.0 Ecoply product range ................ 2 1.1 The Ecoply brand ......................... 2 1.2 Product description & range ..2-3 1.3 Surface grades ............................... 4 1.4 Preservative treatment ............... 5 1.5 Section properties........................ 6 1.6 Product identification .................. 7 1.7 Code compliance.......................7-9 1.8 Sustainability ................................ 10 1.9 Health & Safety ........................... 10 1.10 Storage & Handling .................... 10 1.11 Limitations.................................... 10 2.0 General installation guide ......... 11 2.1 Framing ......................................... 11 2.2 Nailing and fixing sheets ........... 11 2.3 Adhesives ..................................... 12 2.4 Durability...................................... 12 3.0 Common applications ............... 13 3.1 Structural bracing ....................... 14 3.1.1 Description and purpose.......... 14 3.1.2 Design to comply with the New Zealand Building Code ...14-16 3.1.3 Bracing ratings for Ecoply ...... 17 3.1.4 Installation ..............................19-23 3.2 Linings and claddings ................. 24 3.2.1 Frame spacings ............................ 24 3.2.2 Curved shapes ............................ 24 3.2.3 Stucco ........................................... 24 3.3 Floors, Roofs and Decks........... 26 3.3.1 Span Tables ................................... 26 3.3.2 Plywood selection ...................... 28 3.3.3 Roofing Types .............................. 30 3.3.4 Installation .................................... 32 3.3.5 Finishing Floors ........................... 34 3.6 Plywood packaging ..................... 35 4.0 Frequently asked questions ..36-37 5.0 References & sources of information .................................. 38
product quality control programme to monitor compliance with AS/NZS 2269:2008 Plywood Structural. As such these products carry Engineered Wood Products Association of Australasia (EWPAA) Joint Accreditation System Australia and New Zealand (EWPAA/JAS-ANZ) certification. This manual has a sister publication, the Ecoply Appearance Product Manual, which covers BB, BD and grooved lining (often referred to as Plygroove) Ecoply products used in applications where visual appearance as well as structural performance is important. For information relating to Shadowclad, refer to the Shadowclad Unlimited Possibilities consumer brochure and Shadowclad Specification & Installation Manual.
The information contained in this manual relates to specific Ecoply branded plywood products manufactured by Carter Holt Harvey Woodproducts and their correct specification and installation. This manual cannot be relied upon when using other plywood products however similar they appear. Alternative plywood products can differ in a number of ways which may not be immediately obvious and substituting them for Ecoply products may not be appropriate and could in extreme cases lead to 2 premature failure and/or buildings which do not meet the requirements of the New Zealand Building Code.
Preservative treatment, being untreated, H3.2 CCA or H3.1 LOSP Azole treated. Edge finish, being square edge or for Ecoply Flooring, Ecoply Roofing, routed on the long edges of the sheet with a polypropylene plastic tongue inserted into one side for a tongue-in-groove joint. See Table 1 Ecoply product range opposite.
9 (3 ply)
Identification code*
7-24-3
9-30-3
Layup
2.4/2.4/2.4
3/3/3
Product and grade 2400x1200 2400x1200 2700x1200 2400x1200 2700x1200 2400x1200 2700x1200 2400x1200pt 2700x1200pt 2400x1200pt 2700x1200pt 2400x1200pt 2700x1200pt 2400x1200pt 2700x1200pt Available either untreated or H3 LOSP 2700x1200pt 2400x1200pt 2700x1200pt 2400x1200pt 2700x1200 2700x1200 2700x1200 2400x1200pt LS 2700x1200pt LS 2400x1200 2400x1200 2400x1200 2700x1200 2700x1200 2700x1200 2400x1200 2400x1200 2400x1200 2400x1200 2700x1200 2400x1200 2700x1200 2400x1200pt 2700x1200pt 2400x1200 2700x1200 2400x1200 2700x1200 2400x1200pt 2700x1200pt 2400x1200 2400x1200 2400x1200
Ecoply Structural
BB
(Square Edge)
BD
BD
CD
2400x1200
2400x1200
CD
2700x1200
2700x1200
DD
2400x1200
2400x1200
DD
2700x1200
2700x1200
Ecoply Flooring
CD
CD
Ecoply Roofing
DD
DD
Ecoply Grooved
CLASSIC
Lining
CLASSIC
PIONEER
PIONEER
Available H3 CCA
* pt LS Note
Identification code is Thickness (mm) Face veneer thickness (mm x 10) Number of veneers. Machined grooves on both long edges with a plastic polypropylene tongue in one groove, 1200mm cover. Longspan flooring, which has higher stiffness than F8 for superior spanning capability. Full range may not always be available ex-stock, check with Ecoply supplier to ensure availability. Non-standard specifications, including thicker sheets may be available to special order in significant quantities. All products are F8 stress grade except Ecoply Roofing, which is F11 and Ecoply Longspan flooring, which has higher stiffness than F8. Note, Ecoply Flooring products are also available in F11 on request.
ECOPLy GROOvED LINING: CLASSIC Recommended for clear and stain finishes.
PIONEER May contain traces of synthetic filler. Recommended for paint finishes.
ECOPLy STRUCTURAL
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Structural appearance grade with minor repairs. Suitable for high quality paint finish. Some suggested uses Furniture Joinery Interior lining Sheathing Signs Engineering components where a higher finish is required
Solid sanded surface with filled holes and splits, with smaller intergrown knots. Suitable for a basic paint finish. Some suggested uses Concrete formwork Structural gussets Roof decking under tiled systems Bins, boxes, crates Subsheathing Hoardings Stressed skin panels
#
Usually sanded surface with unfilled holes up to 75mm across the face veneer. Splits and knots also allowable. Some suggested uses Box and C beams Portal frame webs Gussets Roofing under asphalt shingles Crates Strength critical pallets
#
Ecoply Flooring CD
(Has a higher quality crossband under the face) Some suggested uses T&G Flooring Roof decking under rubber membranes Most other roofing H3 CCA water based treated substrate for flexible membranes
Ecoply Roofing DD
(Unsanded to allow grip for workers on sloping roofs) Some Suggested uses T&G underlay for asphalt shingles Roof systems where a smooth substrate is not required
Colour code paint stripes indicating grade are applied to one end and one edge of each panel on Ecoply Structural CD and DD only.
Note: A higher visual grade may be subsituted if required e.g. Ecoply CD can be used anywhere DD is used. Ecoply Flooring (CD grade) should be used rather than Ecoply CD square edge panels as a substrate for membrane decks. See section 3.3 Floors, Roofs and Decks. The pictures shown above are a scaled down version of a typical sheet of Ecoply. Grain pattern and colour may vary. If critical, select panels by hand.
ECOPLy STRUCTURAL
Plywood for dry interior use, Dried after treatment to supplied ex mill at average 18% moisture content <15% moisture content for use in service at higher moisture contents Readily available Standard treatment except for BB, BD, Ecoply Grooved Lining and Shadowclad
Availability
CCA Ecoply Structural plywood, which is H3.2 CCA treated (waterborne preservative with a green colour), is dried following treatment so that sheets may return to the correct dimensions. The moisture content after treatment with CCA and drying will be higher than the limits placed in AS/NZS 2269 on untreated product because treated plywood needs to be suited for use in the in-service hazard class environment. The target is for an average moisture content of approximately 18% to provide a panel closer to the expected equilibrium moisture content for most H3.2 applications. The fillets used to separate sheets in drying may leave marks on the sheet surface. These will fade over time as the plywood weathers, and can be disguised with paint but may be visible under stain. The process of treating with CCA and subsequent drying is likely to increase the face checking of the panel. Refer Woodproducts NZ Technical Note 01/06/62 CCA Ecoply plywood surface quality. LOSP, painting and gluing LOSP treated Ecoply uses colourless solvent to retain the wood colour and is moisture inert so the plywood remains at the same dimensions and moisture content. However, the plywood when freshly treated may contain more than 60 litres of organic fluid per cubic metre. Much of this needs to evaporate before painting to ensure adhesion of paint films. The solvent smells quite strong and venting is recommended for interior use or storage until most of the solvent has evaporated. Mechanical fasteners are recommended to fix LOSP treated Ecoply to framing. If adhesives are required, thorough venting is recommended and LOSP tolerant adhesives should be applied according to adhesive manufacturers instructions. A suggested adhesive to fix LOSP treated Ecoply to framing, or to fix untreated panels to LOSP treated framing, is Bostik GIBFix All-Bond or Bostik Gold. (see page 12). Face checking is caused by weathering, especially on northern facing exposures. Face checks are lengthwise separations of wood fibres in the face veneer of the plywood. They result from the normal swelling and shrinkage of wood as it gains and loses moisture. It is important to realise that these checks are superficial, being confined to the face veneer. They do not alter the structural integrity of the plywood. Because face checking is considered normal, it is not limited by the manufacturing specifications for Ecoply.
ECOPLy STRUCTURAL
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Perpendicular to the face grain Cross Section Area A (mm2) 4.87 6.09 7.34 9.18 9.82 11.0 12.2 13.8 12.3 15.3 Moment of Inertia I (mm4) 2.05 4.01 33.4 65.2 122 134 157 113 239 381 Section Modulus Z (mm3) 1.71 2.67 9.27 14.5 20.4 22.3 23.8 18.5 31.9 41.0 Shear Constant I/Q (mm2) 2.30 2.87 5.45 6.81 9.47 9.50 10.7 10.4 11.8 13.9 Cross Section Area A (mm2) 2.54 3.18 5.02 6.27 7.49 6.30 7.60 5.80 9.36 10.1
Mass
Moment of Inertia I (mm4) 30.0 58.6 115 225 285 273 451 476 556 897
Section Modulus Z (mm3) 8.33 13.0 19.2 29.9 33.9 32.5 46.9 50.1 52.9 72.9
Shear Constant I/Q (mm2) 5.19 6.48 9.26 11.6 12.2 12.3 13.7 13.3 15.2 17.8
(kg/m2) 4.0 5.0 6.6 8.3 9.2 9.2 10.6 10.5 11.6 13.5
Table 4b: Nominal strengths of sections of Ecoply Structural plywood for Limit States Design: F8 grade
Nominal strengths (Limit States) per mm width Parallel to the face grain Nominal plywood thickness (mm) 12 15 17 17 19 19LS 21 25 Actual thickness (mm) 12.0 15.0 16.8 16.8 19.2 19.0 21.0 24.6 12-24-5 15-30-5 17-24-7 17-24-6 19-30-7 19-30-7 21-30-7 25-30-9 ID code Weight Bending Stiffness EI (1000 Nmm2) 1046 2043 2589 2484 4104 4329 5057 8160 Bending Moment fZ (Nmm) 479 748 847 813 1173 1252 1323 1823 Rolling Shear fl/Q (N) 15.74 19.68 20.66 20.91 23.29 22.68 25.83 30.26 Axial Compression fA (N) 147 184 196 220 244 275 245 306 Bending Stiffness EI (1000 Nmm2) 304 593 1115 1219 1429 1028 2177 3467 Perpendicular to the face grain Bending Moment fZ (Nmm) 232 362 510 558 595 463 797 1025 Rolling Shear fl/Q (N) 9.26 11.6 16.1 16.2 18.2 17.7 20.1 23.6 Axial Compression fA (N) 100 125 150 126 152 116 187 202
Table 4c: Nominal strengths of sections of Ecoply Structural plywood for Limit States Design: F11 grade
Nominal strengths (Limit States) per mm width Parallel to the face grain Nominal plywood thickness (mm) 15 17 17 19 21 25 Actual thickness (mm) 15.0 16.8 16.8 19.2 21.0 24.6 15-30-5 17-24-7 17-24-6 19-30-7 21-30-7 25-30-9 ID code Weight Bending Stiffness EI (1000 Nmm2) 2362 2992 2867 4736 5838 9418 Bending Moment fZ (Nmm) 1046 1186 1137 1641 1851 2551 Rolling Shear fl/Q (N) 24.36 25.62 25.83 28.77 31.92 37.38 Axial Compression fA (N) 229 245 275 305 307 382 Bending Stiffness EI (1000 Nmm2) 593 1115 1219 1429 2177 3467 Perpendicular to the face grain Bending Moment fZ (Nmm) 362 510 558 595 797 1025 Rolling Shear fl/Q (N) 11.6 16.1 16.2 18.2 20.1 23.6 Axial Compression fA (N) 125 150 126 152 187 202
* Identification code: panel thickness outermost veneer thickness x 10 number of plies. I/Q values for rolling shear are for stress at the neutral axis calculated as in NZS 3603. For tension, multiply compression values by 0.75.
Use Tables 4a & b values for all F8 stress grade Ecoply products including Ecoply Longspan Flooring and Shadowclad Texture. Use Tables 4a & c values for all F11 stress grade Ecoply. Ecoply 19mm Longspan Flooring has F8 strength properties but higher E of 10000 MPa. For Shadowclad groove (a 5 ply grooved panel), Use tabled values for F8 parallel to the face grain, Perpendicular to the face grain multiply bending stiffness in Table 4b by 0.35, and use 3 ply values for strength. The section properties in Tables 4a, b & c have been calculated in accordance with AS/NZS 2269. For other thicknesses, consult Woodproducts NZ on 0800 ECOPLy for section properties. For 19LS (i.e. Longspan), EI parallel to the grain in Table 4b may be increased by 10%. These panels are manufactured with stiffer face and back veneers to improve flooring performance.
ECOPLy STRUCTURAL
911
If the plywood is treated, it will also be marked in accordance with the treatment Standard AS/NZS 1604.3:2004 Specification for Preservative Treatment, Part 3: Plywood.
Structural properties of Ecoply plywood The majority of Ecoply Structural plywood is F8 grade (exceptions are identifed in section 1.2 Product Description & Range) and the characteristic values may be used in conjunction with both NZS 3603 and AS 1720 for the design of timber components. The characteristic stress values in Table 5 have been used to provide nominal strengths in Tables 4b and 4c. Table 5: Structural properties of Ecoply plywood Characteristic stress value MPa F8 Bending Tension Panel shear Rolling shear Compression (in plane) Bearing (normal) Modulus of elasticity E Modulus of rigidity R
Source: AS/NZS 2269:2004
ECOPLy STRUCTURAL
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Wood is strongest when stressed parallel to the grain and weakest across the grain, so the lay up or arrangement of veneers in the panel determines the properties. Because of its cross banded construction, plywood possesses significant strength and stiffness both parallel and perpendicular to the direction of the face grain, but is generally strongest and stiffest along the direction of the face grain. The section properties of structural plywood in Table 4a are calculated in accordance with AS/NZS 2269 to allow for the reduced contribution of veneers perpendicular to the direction of stress. For engineering design to NZS 3603, the section properties are multiplied by stresses and k factors to determine resistances for working stress design, or nominal strengths for limit states design. Resistances and nominal strengths in Tables 4b and 4c assume all k factors are equal to 1.0. Multiply tabled values by the strength reduction factor and k factors for specific in-service conditions for design to a structural code such as NZS 3603. Durability and exterior moisture E2 Ecoply plywood is made from softwood solid radiata pine veneer. Designers should assess the level of exposure to biological, moisture, and other hazards and apply appropriate preservative treatment and detailing to minimise exposure to these hazards. The designer or builder can make or break durability compliance. Information in this manual outlines suggested practices for detailing building components to exclude moisture to comply with the durability requirements of the NZ Building Code. Woodproducts NZ Durability statement, 01/11/10 includes further guidelines for some environments and applications. Formaldehyde Ecoply plywood is manufactured using phenol formaldehyde resins which are fully cured in the hot press. Cured resin is thermally and moisture stable and formaldehyde emissions for the glued plywood are similar to background levels for the wood by itself when tested to AS/NZS 2098.11 Determination of formaldehyde emissions for plywood. Accordingly every Ecoply panel is branded with the lowest emission class (less than 0.5mg/litre for E0). Actual emissions measured are usually much less than background levels in the air we breath (0.03 mg/litre).
Moisture content and dimensional change At the time of leaving the factory, the moisture content of untreated Ecoply plywood should generally be in the range of 8% to 15% as required by AS/NZS 2269. All wood products including plywood respond to changes in ambient humidity so the eventual moisture content of plywood varies according to how dry or how wet the environment is. After manufacture, the moisture content will move to equilibrium with the environment, and the veneers swell or shrink across the grain in response. The total expansion both along and across a 2400x1200mm panel can be in the order of 1.5mm to 3mm as the plywood changes from a dry to a saturated state. Ecoply that is treated with waterborne salts (e.g. CCA) is expected to be used in applications that have higher humidity than interior dry use, so following treatment it is dried to a higher average moisture content of approximately 18%. This provides for a more stable panel in service than placing a dry (less than 15%) sheet in a higher moisture environment. Detailing and construction must allow for movement if the plywood will be subject to cycles of moisture change. Seasonal and daily cycles can be significant depending on the end use. Temperature Wood (and plywood) expand upon heating as do practically all solids. The thermal expansion of plywood is quite small and there is little effect on the structural performance or durability of plywood when used in temperatures below 54C. The average co-efficient of thermal expansion of plywood is 4.5 x 10-6 mm/mm/C. At temperatures above 55C wood begins to deteriorate. Colours of coatings and finishes should be selected to reduce heat gain. For extreme conditions, further technical information is available by calling 0800 326 759. The thermal resistance or insulating effectiveness of plywood panels can be calculated using NZS 4214:2006. e.g. Plywood has a conductivity (k) of 0.13 W/mK so a 12mm panel has a thermal resistance R = 0.012/0.13 = 0.09. Aesthetics Ecoply products can be selected for decorative or weather protection functions as well as structural performance. Acceptable Solution E2/AS1 External Moisture allows plywood manufactured to AS/NZS 2269, minimum CD appearance grade, minimum 5 ply, minimum 12mm thickness and treated as required by NZS 3602 to be used for exterior cladding. For exterior cladding applications Woodproducts NZ strongly recommends Shadowclad, which has a bandsawn face to help reduce the incidence of face checking. See footnote on page 5. Shadowclad is available with and without vertical grooves.
ECOPLy STRUCTURAL
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ECOPLy STRUCTURAL
10
1.8 Sustainability
Ecoply is manufactured from radiata pine, a plantation grown medium density softwood. It is grown on tree farms which are tended and harvested to provide wood for plywood manufacture. The crop is managed on a sustainable basis to yield millable trees. New Zealand plantations are managed in compliance with the New Zealand Forest Accord, a voluntary agreement signed in 1991 between NZ forest managers and environmental non-governmental organisations. Ecoply is manufactured in New Zealand at Woodproducts NZs Tokoroa plywood mill. Ecoply and Shadowclad are available Forestry Stewardship Council (FSC) certified upon request.
1.11 Limitations
The information contained in this document is current as at March 2009 and is based on data available to Carter Holt Harvey at the time of going to print. This publication replaces all previous Carter Holt Harvey design information and literature relating to Ecoply Structural, Ecoply Bracing, Ecoply Flooring, Ecoply Roofing & Decking and Origin plywood. Carter Holt Harvey reserves the right to change the information contained in this document without prior notice. It is important that you call 0800 326 759 to confirm that you have the most up to date information available and refer to www.ecoply.co.nz. Carter Holt Harvey has used its reasonable endeavours to ensure the accuracy and reliability of the information contained in this document and, to the extent permitted by law, will not be liable for any inaccuracies, omissions or errors in this information nor for any actions taken in reliance on this information.
ECOPLy STRUCTURAL
2.1 Framing
Use kiln dried framing e.g. Laserframe in accordance with timber framing manufacturers specifications and treated in accordance with NZS 3602. All timber frame sizes and set out must comply with NZS 3604 (or be specifically designed to NZS 3603). Ecoply may be specified for frame spacing determined by design, or using tables in section 3 for specific product applications such as bracing, exterior cladding, flooring and as a substrate for shingle roofs or membrane roofs and decks. LOSP treated framing should be vented before fixing and if construction adhesives are required (for example to screw and glue floor panels) the adhesive must be compatible with LOSP (See 1.4 Preservative treatment).
Self tapping, self countersinking screw Screw Numbers indicate: Gauge Threads per inch Length (mm) The load is the characteristic load (N) for one fastener in single shear
Steel thickness, screw sizes, characteristic loads, refer to assemblies actually tested. Other screw sizes may be used. Screw properties vary between screw suppliers and the suitability of a particular size should be verified by the designer for performance under changing physical conditions and cyclic loading. Non-standard nailing may be specifically designed with NZS 3603 or similar.
11
ECOPLy STRUCTURAL
12
2.3 Adhesives
Tube applied construction adhesives Site applied construction adhesives may be used together with nails and screws for non permanent loads, reduced fastener popping, and to lower the risk of squeaking in floors. Available types include polyurethane (e.g. Hold fast Gorilla Nail Power) and elastomeric (e.g. Bostik Wallboard Gold) based adhesives. Elastomeric adhesives should meet the requirements of APA Performance specification AFG 01 Adhesives for field gluing plywood to wood framing. Other types should have appraisal from BRANZ or equivalent authorites for the specific applications proposed. Follow manufacturers recommendations as follows: Use a bead or dabs of adhesive as per manufacturers recommendations Apply pressure using fastener patterns outlined in section 2.2. Work from the middle of the sheet outwards to develop glueline pressure. Ensure adhesives are compatible with treatment in the framing timber (see page 5, LOSP, Painting, Gluing.) Structural adhesive joints Structural bonds are generally only achievable in factory controlled conditions using approved structural adhesives in accordance approved standards for glue lamination, e.g. Resorcinol formaldehyde joints made to AS/NZS 1328 Glued laminated structural timber. Site gluing is not recommended for structural plywood components. Contact the Ecoply help line for further information.
2.4 Durability
The durability of Ecoply Structural plywood will depend on the application. Detailing, treatment and installation details need careful consideration to satisfy the requirements of the New Zealand Building Code. Normally, 50 year durability can be achieved with untreated Ecoply in dry, interior exposure. For internal environments subject to high humidity or condensation H3 treated Ecoply should be used. Unpainted H3 treated Ecoply in exterior applications will weather and oxidise and although panels can be expected to last approximately 15 years, the lack of protection will lead to various shades of grey with surface checking and black surface mould growth. Ecoply should not be left unpainted if long term durability is required. Treatment can mitigate risk from fungal and insect organisms, but sun and rain can thermo-mechanically degrade the surface of panels and the surface veneer of plywood is often strength critical. Light coloured, maintained, flexible acrylic paint systems offer best results for long term durability. To achieve the 50 year durability requirement of the New Zealand Building Code in accordance with NZS 3602, H3 treated Ecoply exterior cladding used as a bracing element, must be coated with a regularly maintained flexible paint system such as a three coat acrylic latex paint system with a light reflectance value (LRv) of 40% or more. For bracing in cavities behind another cladding system, e.g. brick veneer, H3 treatment without coating is sufficient. For single story brick veneer houses with 450mm minimum eaves untreated exterior wall framing and bracing plywood is permitted in NZS 3602.
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BRACING
14
14
Durability Ecoply plywood is manufactured to meet the requirements of NZS 3602 Timber and Wood based products for use in Buildings. If the product is used, handled and installed in accordance with Woodproducts NZ product literature it will meet the durability clauses of the NZ Building Code. Table 7 summarises the applications in which Ecoply and Shadowclad can be used as structural bracing together with the preservative treatment requirement and fastener material for corrosion resistance.
BRACING
Table 7: Ecoply and Shadowclad suitability for bracing applications including treatment type and fastener material Application Plywood bracing protected from the weather but with a risk of moisture penetration conducive to decay: e.g. plywood bracing and/or rigid underlay (air barrier), fixed to framing with/without building paper/wrap over, with/without cavity battens behind cladding Plywood bracing exposed to exterior weather conditions and dampness but not in ground contact: e.g. plywood as both cladding and bracing (direct fixed to framing or over a 20mm drained ventilated cavity system) Bracing walls where the timber framing is not required to be treated in accordance with NZS 3602 Bracing on framing exposed to ground atmosphere (subfloor) Bracing in wet process buildings Plywood Type Ecoply H3 treated , DD surface grade or better
1
Stainless steel5 or silicone bronze (as per Table 4.3 of NZS 3604:19993)
Hot dipped galvanised or better Stainless steel5 or silicone bronze Stainless steel5 or silicone bronze
Ecoply H3 is plywood that has been preservative treated to the H3.2 hazard rating with CCA type preservative. Shadowclad plywood cladding products are preservative treated to H3.1 hazard rating with a LOSP azole system. Refer to the Shadowclad Specification & Installation Manual. Plywood used as both cladding and bracing must have a three coat maintained acrylic exterior paint system with a light reflectance value of 40% or greater for 50 year durability. Galvanised steel/protected galvanised steel nails are unsuitable for use with Ecoply H3.2 CCA treated plywood. Moisture content in plywood and adjacent timber must be less than 18% in service. Stainless steel nails must have annular grooves to provide similar withdrawal resistance to hot dipped galvanised nails.
3 4 5
Detailing near doors and other fittings must avoid the collection of debris which could damage the plywood surface. Battens and other items attached to the surface shall have capillary breaks and surfaces that encourage drainage of water and shedding of debris. Acceptable Solution E2/AS1 requires plywood claddings to be a minimum of 12mm in thickness and grade CD or better. Woodproducts NZ recommends the use of Shadowclad rather than Ecoply for exterior cladding (Refer page 24 and Shadowclad Specification & Installation Brochure).
15
BRACING
16
Rain wetting and construction bracing Untreated Ecoply will withstand rain and exposure during construction for up to 3 months. Rain and exposure can cause thinner plywood panels to buckle. Plywood stability is related to the number of veneers and thickness of the panel. Where panel stability is critical, consider using thicker panels. Humidity and condensation In uses where the moisture content may exceed 18% for prolonged periods, Ecoply must be H3 treated to resist decay or insect hazard. Subfloor sheet bracing H3 treated Ecoply can be used as sheet bracing where dampness does not allow the use of untreated plywood or other sheet materials (clause 5.4.3 of NZS 3604:1999). Where Ecoply subfloor sheet bracing is exposed to both rain and sun, it must be coated with a three coat maintained acrylic exterior paint system with a light reflectance value of 40% or greater. Cladding as bracing H3 treated Ecoply and Shadowclad can be used as cladding as well as bracing. To achieve 50 year structural durability, it must be: Surface grade CD or better A minimum of 5 ply A minimum of 12mm thickness Coated with a three coat acrylic paint system with a light reflectance value (LRv) of 40% or more Fixed with stainless steel or silicone bronze fasteners Refer to the Shadowclad Specification & Installation Manual for details. Woodproducts NZ recommend Shadowclad for exterior cladding. Shadowclad has a bandsawn face which helps reduce the incidence of face checking (see footnote on page 5) and is H3.1 treated with LOSP Azole, a clear preservative which does not leave fillet marks on the face of the panel. 12mm Ecoply CD H3.2 CCA will meet the requirements of Acceptable Solution E2/AS1 and perform as a structural, durable and weathertight cladding and bracing element when correctly installed. However, Ecoply BD H3.1 LOSP is recommended where a higher appearance grade is desired with a clear finish preservative treatment and no fillet marks. (H3.2 CCA has a green tinge and the treatment process leaves fillet marks on the face of the sheet). Fasteners Use corrosion resistant fasteners appropriate to the expected life cycle exposure for the bracing element. Refer Table 7. Where H3.2 CCA Ecoply is used, it must be fixed with stainless steel or silicone bronze fasteners. Soil Ecoply (untreated or H3 treated) and Shadowclad must not be allowed to come in contact with soil. The bottom edge of the plywood sheet must be a minimum of 100mm above decks or paved ground and a minimum of 175mm above unprotected ground.
BRACING
BRACING
*
Maximum Stud Spacing (mm) 450 600 600 450/600 450/600 450 or 600 450 600 450 600 600
Ratings for Ecoply component on one side only SP4 SP2* (Timber) (Concrete) SP1* (Timber) (Concrete) SP6 SP8D SP5D SP10 SP12* (Timber) (Concrete) SP2G SP1G
1 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1 1 2
70 90 90 110/100 100/100 115 125 130 135 120 115 95 110 140 130 135 120 145
85 80 105 105/100 115/100 110 135 135 135 105 105 95 105 120 100 140 110 135
Ratings for Ecoply one side and GIB plasterboard on the other side 150 150 150 150 150 150 150 600 450 or 600 450 or 600 450 or 600 450 or 600 450 or 600 450 or 600
SP11G
Wall type codes SP = Structural Plywood D = Double hold down strap (i.e. 2 x 6kN hold down straps at each end of the wall bracing element). Where wall type code does not include a D, a single 6kN hold down strap is required at each end of the wall bracing element. G = 10mm GIB Standard plasterboard or any other GIB plasterboard, nailed as per GIB Standard plasterboard. BLP = Winstone Wallboards bracing element - refer Winstone Wallboards Ltd literature. These walls on timber and concrete floors reviewed by BRANZ. Where floor type is not specified, use the lower value.
** Use these nail spacings at all sheet edges. Within the sheet, nail spacings may be double that specified. *** See Installation section on page 19. 1 denotes a single 6kN hold down strap is required at each end of the wall bracing element and 2 denotes two 6kN hold down straps are required at each end of the wall bracing element. Straps are not required for every Ecoply bracing panel, only at each end of the wall bracing element. BLP denotes Ecoply on one side in accordance with this literature and 10mm GIB Braceline in accordance with Winstone Wallboards Ltd instructions. The GIB may be 10mm GIB Standard plasterboard or any other GIB plasterboard except system BLP where 10mm GIB Braceline is required. GIB may be fixed horizontally or vertically (refer to GIB Bracing Systems manual for installation details and limitations, available at www.gib.co.nz or by calling 0800 100 442).
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Fasteners Use any of the following fasteners with untreated Ecoply 7mm bracing. For H3.2 CCA treated Ecoply bracing required for those applications shown in Table 7, the stainless steel or silicone bronze fastener options must be used. For fixing Shadowclad used as bracing as well as cladding, refer to the Shadowclad Specification & Installation Manual. 30 x 2.5mm galvanised clouts (flat head) 40 x 2.5mm galvanised clouts (flat head) Paslode Impulse RounDrive (full round head) 50 x 2.87mm, Hot Dip Galv. ring nail (B20557) 40 x 2.8mm stainless steel annular grooved nails (flat head) 40 x 2.8mm silicone bronze annular grooved nails (flat head) Paslode 55 x 2.8mm Lense Head (Full Round Head) 304 stainless steel ring nails, plastic collated (B20572) For 9mm Ecoply use minimum length 40mm nails. For 12mm Ecoply use minimum 50mm length nails. Adjustments for wall height Use clause 8.3.1.4 of NZS 3604 to calculate bracing values: Adjustment of bracing capacity of walls of different heights and walls with sloping top plates shall be obtained by the following method:
BRACING
18
(a) For wall bracing elements of heights other than 2.4m, the bracing rating determined by test or from Table 8.1 should be multiplied by 2.4 element height in metres, except that elements less than 1.8m high shall be rated as if they are 1.8m high. (b) Walls of varying heights, should have their bracing capacity adjusted in accordance with 8.3.1.4(a) using the average height. Joining panels for walls higher than maximum sheet length Ecoply bracing panels must be fixed from top plate to bottom plate. For wall heights over 2.4m, Ecoply is available in 2.7m sheet lengths. Alternatively, a part sheet can be stacked above a full sheet, butt joined on a single row of nogs with each sheet/part sheet independently nailed off as per the nail spacing in Table 8 (e.g. 2.4m x 1.2m sheet with a 0.3m x 1.2m part sheet above it to give a 2.7m x 1.2m bracing element).
BRACING
Ecoply Bracing
BRACING
3.1.4 Installation
Framing Framing must be in accordance with NZS 3604. Before placing the frame in position, check the hold-down requirements to enable positioning of any straps required. Refer to Figure 2 for detailing of expansion gaps and framing alignment. Nogging for horizontal joints between sheets should be at least 35mm wide to enable nailing of both sheet edges. Hold-down details Hold-down straps are available through builders supply merchants in a range of lengths from 200mm to 600mm. A standard 6kN hold down strap is pre-galvanised 25mm x 0.91mm (nominal 1mm). Straps are also available in 0.91mm stainless steel 304-2B which must be used if the strap will be exposed to the weather or will be in direct contact with H3.2 CCA treated Ecoply or other corrosive timber. Fix pre-galvanised hold-down straps with 30 x 3.15mm flat head galvanized nails and stainless steel straps with 30 x 3.15mm flat head stainless steel. Refer to Figure 2. Where strap projects into subfloor space, use additional protection in accordance with NZS 3604 clause 4.4.5. Type 1 (6kN) hold-down At each end of the wall, use either: A single 25mm x 0.91mm sheet brace strap. Refer to: Figure 2 or, The dropped panel detail, requiring no straps. Refer to: Figure 2(a) and 2(c) Type 2 (12kN) hold-down Higher wall ratings are possible with double hold-down and/or double nailing. For Type 2 hold-down use two 25mm x 0.91mm straps, one on each side of the end stud. On concrete floors, a single strap may fold under the plate and up both sides of the stud. Nailing and fixing of sheets Refer Figure 2(a). Nail according to the desired bracing rating in Table 8 and the notes with the table. Allow a 2 to 3mm wide expansion gap between sheets (Figure 2(b)). Nails must be at least 7mm from the edge of the sheet for square edge sheets and 7mm plus the width of the top lap for Shadowclad shiplap edges. Do not nail through the top laps of Shadowclad shiplap edges (Figure 2(b)). For more detailed instructions refer to the Shadowclad Specification & Installation Manual. Nail all sheet edges (including those with plastic tongue-in-groove joints) and all ends of the sheets used as bracing to the requirements of Table 8. Sheets with plastic T & G joints will require solid blocking behind joints if use for bracing. Do not foul hold-down straps and nails used to fix the plywood. This weakens the strap below specification. For power driven nails, use the Paslode Impulse Compact Nailer fitted with a No Mar(k) work contact element. Adjust work contact element to the flush position and drive nail flush with the plywood surface. Hammer any nails flush which are left proud. Do NOT overdrive power driven nails. Openings in bracing elements Small openings (e.g. power outlets) of 90 x 90mm or less may be placed no closer than 90mm to the edge of the braced element, or waste pipe outlets of max. 150mm diameter placed at no closer than 150mm to the edge of the braced element.
19
BRACING
20
ECOPLY BRACING OR CLADDING Ex 2745 LONG SHEETS. ECOPLY BRACING (2700 mm LONG) OR SHADOWCLAD (2745 mm LONG)
STRAP DETAILS (SEE FIGURE 2d-2h) FIXING TO NOGS NOT REQUIRED SHEET LENGTHS 2400 AND 2700 DROPPED PANEL DETAIL (SEE FIGURE 2(c)
BRACING
Note 1. Nail centres given for standard nailing, refer Table 8. 2. Extra hold-down nails are same size as for rest of sheet.
Figure 2(d): Type 1 strap fixings to each end stud of plywood sheet braces for timber ground floor and upper storey
Note: 1. Detail (a) can be replaced by a dropped panel fixing with no straps. See Figure 2(c).
21
BRACING
22
Figure 2(e): Type 2 strap fixings to each stud of plywood sheet braces for timber
Figure 2(f): Type 1 strap fixings and capacities to each end stud of braced panels on concrete
(a) Type 1 strap one side and under plate 6 30 x 3.15mm dia. Galv. F.H. nails each end
(b) Embed M12 bolt with 50 x 50 x 3mm washer, cranked and embedded 75mm into concrete or proprietary fixing
(c) Type 1 strap wrapped under plate 3 30 x 3.15mm dia. Galv. F.H. nails each end of strap
BRACING
Figure 2(g): Type 2 strap fixings to end studs of plywood sheet braces for concrete floors
(a) 25 x 1 mm galvanised sheet brace strap wrapped under plate 6 - 30 x 3.15 mm dia. Galv. F.H. nails each side of stud (b) Concrete base
100mm max. for type 2 fixing M12 bolt with 50 x 50 x 3mm washer, cranked and embedded 75mm into concrete or proprietary fixing
Figure 2(h): Typical detailing for wall and subfloor framing on concrete floor and foundations
Note: Modify these details for either Type 1 or Type 2 fixings according to Figure 2(f) or Figure 2(g)
23
Note: Sheets are fixed along framing when applied vertically to studs and across framing when applied vertically to girt or
3.2.3 Stucco
Stucco claddings should be installed in accordance with the requirements of NZS 4251:2007 and NZBC Acceptable Solution E2/AS1 External Moisture or the relevant manufacturers Alternative Solution. Ecoply Structural plywood is an effective rigid backing sheet. Use Ecoply H3.2 CCA treated DD grade or better.
All stucco claddings should be used over a drained cavity with: building wrap fixed to the framing and building wrap as an overlay to the Ecoply rigid backing to provide a slip layer that permits the independent movement of plaster and backing. Table 9 provides more plywood thickness options and spans than NZS 3604 or E2/AS1, including specifications for thinner Ecoply backings which may be more practical for curved walls and thicker Ecoply for greater spans between girts. Paragraph 11.8.2 of NZS 3604 requires rigid backings to be supported on studs at 600mm maximum centres with evenly spaced rows of dwangs at maximum 800mm centres. Paragraph 9.3.6.1 of E2/AS1 refers to Table 5 of NZS 4251 to determine required plywood sheet thickness. Spans shown in bold in Table 9 for 9mm, 12mm and 15mm Ecoply thicknesses are in accordance with NZS 4251. All other spans in Table 9 are based on Woodproducts NZ calculations and designers should satisfy themselves these are suitable for the specified coating. It is critical to provide expansion gaps (3mm) between at all sheet edges for Ecoply rigid backings under stucco. All edges of Ecoply sheets must be supported and fixings must be 10mm from sheet edges. Ecoply must be fixed with stainless steel fasteners at 150mm centres around the perimeter and at 300mm centres within the body of the sheet. All timber battens must be: nominal 20mm (between limits of 18mm and 25mm in thickness) at least the same width as the stud H3.1 treated in accordance with NZS 3640 Chemical Preservation of Round and Sawn Timber. fixed over the building wrap to all studs. at 300mm centres vertically where studs are at 600mm centres, (i.e. a batten on studs and one in between the two studs fixed to top and bottom plates and nogs) on the studs only where studs are at 400mm centres Cavity spacers (i.e. short sections of cavity batten) set to min 5 slope (1:12) must be used to support the top and bottom sheet edge or provide intermediate support where required (e.g. above window openings). A min 50mm air gap must be allowed at either side of the cavity spacer to allow ventilation and water drainage down the cavity to the exterior. Where cavity battens are fixed by the Ecoply rigid backing fixings (i.e. cavity battens are temporarily fixed during construction as per Acceptable Solution E2/AS1), through the building wrap into the framing, flat head nails must be used which penetrate framing by a minimum 35mm e.g. for Ecoply thicknesses up to 15mm onto a 20mm cavity batten, use 70 x 2.8mm flat head stainless steel nails or Paslode Impulse 75 x 3.06 mm RounDrive ring nail B20573 stainless steel. Battens must be temporarily fixed to the framing during construction using 40 x 2.5mm galvanised flat head nails or Paslode Impulse 50 x 2.8mm (D flat head) power-driven galvanised nails at a maximum of 800mm centres or for intermediate battens between studs, to top and bottom plates and at nogs only. As an Alternative Solution, cavity battens may be structurally fixed using No 1 framing grade and fixed to the framing with 60 x 2.8mm or 75 x 3.15mm, jolt or flat head, hot dipped galvanised nails or Paslode Impulse 65 x 2.87mm (D flat head) power-driven, galvanised nails at a maximum of 300mm centres and staggered 12mm either side of the batten centreline. BRANZ Bulletin 475 (August 2006) provides full details on the structural fixing of battens. Ecoply rigid backing sheets up to 15mm thickness are then fixed to the structural cavity battens using 50 x 2.8mm flat head stainless steel nails or Paslode Impulse B20572 55 x 2.8mm, lense head (full round head), stainless steel, plastic collated ring nails. For 17mm and 21mm, use 60 x 2.8mm flat head stainless steel nails or Paslode Impulse B20573 75 x 3.06mm RounDrive ring nail stainless steel. Ensure that the backing deflection is limited to a maximum of 5mm at the time of plastering. All stucco surfaces shall be sealed by applying a minimum of 2 coats of a latex exterior paint system complying with any of Parts 7, 8, 9 or 10 of AS 3730. Finish colours must have a light reflectance value of 40% or more when measured in accordance with ASTM C1549 or ASTM E903.
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Table 11: Frame spacing for plywood roofs, decks and floors Recommended maximum frame centres (mm) for plywood with face grain across framing Plywood thickness (mm) Application 1. Sub-sheathing Under steel or self supporting cladding for support of building paper or lateral diaphragm action. Sag not critical 2. Sheathing non-trafficable sloping roof >30 Suitable for asphaltic tile or similar roughness roofing mass to 15kg/m2 3. Sheathing non-trafficable low slop roof >10 Suitable for roofing mass to 50kg/m2 4a. Sheathing non-trafficable flat roof >1.5 Suitable for roofing mass to 50kg/m2 4b. Sheathing non-trafficable flat roof >1.5 Suitable for roofing mass to 15kg/m2 5a. Trafficable roof decking Limited by dynamic response of roof as floor 5b. Roof decking to clause 8.5.5.1 c ) of E2/AS1* 6. Domestic flooring 2kPa 1.8kN 7. Institutional and public assembly up to 4kPa 2.7kN 8. Institutional and crowd assembly up to 5kPa 3.6kN 9. Corridors, industrial up to 5kPa 4.5kN 10. Domestic garage floor ** 2.5kPa 9kN 480 480
12 15 17 19# 21 25
800
1200
600
900
900
1200
1350
540 480
900 800
1200 800
1350 900
600 400 600 F11 or LS# 540 F8 480 400 300 300
* The current requirement in AS1 of E2 is extremely conservative when compared with calculations determined for other applications using vM1 Clause 6 and calibrating the spans against codes of practice from North America and Australia. CHH Woodproducts recommends designers consider the alternative solution in row 5a of Table 11 for membrane roofing. ** Provide blocking to all edges of the sheet. # Spans apply to F8 plywood except: spans for 19mm apply to F8 and F11 or LS (which has higher stiffness, but F8 strength values) and 15mm roofing T&G is also F11. Spans otherwise apply equally to square edge or tongue and groove panels. Check Table 1 for availability of grades and lengths to match span multiples in Table 12. Use the next lower recommended frame spacing or thicker Ecoply where appearance is critical. Where 12 and 15mm Ecoply is used on flat roofs, use blocking at 600mm centres to avoid ponding. To suit trusses at 900 centres, 2700 long sheets are available. See Table 12.
Table 12: Frame set outs (mm) to match 2400mm and 2700mm sheet modules 2400mm long 2700mm long 400 450 480 540 600 675 800 900
Limitation for the use of Table 11 Woodproducts NZ does not have access to information about specific designs for specific sites. Table 11 is a guide to estimate the initial selection of a span for design. Each site should be evaluated by qualified persons to ensure all loading parameters and site conditions have been considered, and appropriate changes should be made by the building designer. Many spans have reduced from previous brochures because of more stringent engineering loading requirements in AS/NZS 1170. For some roofing systems, established practices have shown that longer spans are possible. For some exposed sites it may be necessary to use framing at closer spacing. Check fastener requirements as per details on page 33.
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Durability of roofing systems using plywood substrates In general, H3 treatment of the plywood with waterborne preservatives is recommended for roofing. Roofing materials various roofing materials used over Ecoply plywood have different durability expectations, normally in excess of the 15 years required by the Building Code clause B2.3.1b. Durability of the roofing is subject to the specifications, installation and maintenance requirements of the roofing manufacturer. The durability of the Ecoply can only be assured as long as the overlying roofing and detailing excludes moisture. With good building practice and maintenance, roofing materials can be repaired or replaced at regular intervals to achieve life from the Ecoply in excess of the original roofing. With this proviso the durability of Ecoply Structural plywood will be in excess of 50 years if installed in accordance with instructions and limitations in this brochure. Insect resistance Low moisture content of untreated Ecoply must be maintained (by adequate ventilation) for the life of the building. H3 treated Ecoply provides extra protection where necessary. High humidity, condensation and solar driven moisture Where the moisture content of wood may exceed 18% for prolonged periods, Ecoply must be H3 treated with water-borne CCA (Copper Chrome Arsenic) preservative in compliance with NZS 3602:1995 Timber and Wood-based Products for Use in Building, to resist decay hazard. This includes Ecoply used under roof coverings that may be subject to condensation, or where rain moisture soaked in the roof covering can be driven into the Ecoply by the sun. Appropriate building detailing and ventilation is recommended. See the section on ventilation on page 31 in this manual. Good ventilation design can reduce the need for treatment. Bubbling Plywood bubbling occurs when moisture trapped in knot holes in inner veneers expands as the temperature rises. This moisture will dissipate through the face veneer and will not affect the structural integrity of the plywood panel. As membrane coverings can prevent moisture dissipation, Ecoply Flooring (which has a solid cross band veneer) is recommended if the visual appearance of bubbles is not acceptable. Where rubber membranes are being applied, care must be taken to ensure the adhesive is sufficiently dry to prevent trapped glue solvents from causing blistering. Soil Ecoply plywood (untreated or H3 treated) must not be allowed to come in contact with soil. Surfaces, flashings and gutters should be detailed to avoid trapping detritus and moisture. Rain wetting and construction time Untreated Ecoply will withstand a reasonable amount of rain wetting and exposure during construction for up to three months. In extreme weather conditions of high temperature and/or high rainfall this period may be less. Some discolouration and minor checking of the face veneers can be expected if Ecoply is exposed for extended periods. For roofs uncovered for longer periods use H3 treated Ecoply to lower the risk of decay. Return Ecoply to below 18% moisture content before installing moisture sensitive materials, coverings, coatings or adhesives. For best results, protect the Ecoply. Exterior decking Ecoply Structural plywood is not normally recommended for decks where it is permanently exposed to the weather. Exposed Ecoply for decking must be preservative treated to at least H3 hazard class. However a properly detailed Building Code compliant barrier material eg. butyl rubber, vinyl or E.P.D.M should be used to protect Ecoply from rain and sunlight (weathering) exposure. Gutter details Where Ecoply Structural plywood sub-sheathing supports roofing at gutters, a metal drip edge must be provided with appropriate gaps to shed water. Gutters should have a front edge overflow or ends lower than the back to shed water overflow away from framing and sub-sheathing Ecoply (see details on page 31). H3 treatment is recommended for Ecoply sheets that protrude into gutters, with regular maintenance to avoid leaf mould (soil) development. Do not expose untreated Ecoply to gutter splash or moisture. For more information consult the CHH Woodproducts Durability Statement, 01/11/10. Fire Plywood is combustible but may be used as a roof substrate for all purpose groups subject to the provisions of Department of Building and Housing Acceptable Solution C/AS1: clause 7.1 and 7.9. For purpose groups SC and SD a 19 mm Ecoply panel complies with the requirement of 7.11.1. Many different roofing products are now available for use and installation over a plywood substrate. The choice of plywood grade depends on the type of roofing, and on the level of finish required. Ecoply Roofing provides a safe substrate for roofing crews and can eliminate tile battens or purlins from the framing cost.
Allowing for moisture expansion of plywood under roof and floor coverings Membrane suppliers have strongly held different views on the requirements for plywood substrates. The fixing instructions on page 11, 32, and 33 are the starting point but designers must detail joints that allow for expansion in accordance with practices recommended by the chosen membrane supplier. The Woodproducts NZ view, and the recommendation of a number of suppliers here and in North America, has been to allow for expansion and contraction at sheet edges by loosely butting tongue and grooved edges so that the tongues can absorb movement and providing a small gap (2 to 3 mm) between square sawn edges. Use a bond breaking tape over these joints to spread elongation in the membrane over a longer distance than the narrow gap in the joint itself. This tape can double as a rain seal over the sheet edges during construction. Other membrane suppliers believe that sheets should be tightly butted and glued and screwed hard up to each other. This practice constrains movement at the small joint between sheets, but over a wider area requires significant allowance for movement around the perimeter of a roof segment. Junctions between the roof slopes and walls need careful detailing to allow for the potential movement, and movement control joints should be provided at regular intervals to the recommendation of the membrane manufacturer, especially if this method is adopted.
Roof tile systems Most fibreglass, asphalt or wooden shingle or tile systems will tolerate DD grade surface characteristics. Use unsanded Ecoply Roofing (DD grade), or sanded Ecoply of the required thickness in Table 11. The unsanded surface provides extra grip on steeper roofs for roofing crews. A plywood substrate can avoid the cost of battens. Fix tiles according to tile manufacturers specification. Under asphalt shingles use saturated felt underlay over the Ecoply. Check and confirm all of the recommendations above with the manufacturer of the chosen roofing type.
Ventilation and preservative treatment Poorly ventilated spaces can develop very high temperature and moisture levels. The most likely source of moisture is the condensation of vapour from warm interior air on the underside of cold roofing. Good ventilation can remove the need for treatment by removing excess moisture vapour in warmer climates but in regions where winter nights are consistently colder, H3 treated Ecoply is recommended. However, the use of H3 treated Ecoply is not an excuse for poor ventilation design. Moisture induced decay is only one issue. If incorrectly detailed, roof spaces can be very tight and the dark colour of many roofing materials means that excessive heat can build up causing distortion in plywood or even framing members. Use the suggested details or alternatives to suit. Designers must consider roofing type, seasonal conditions, wind effects and the intended use of the building. As a minimum, Woodproducts NZ recommends a vent area of 1/300th of the ceiling plan area (approx 3350mm2 per square metre of ceiling) equally distributed at the eaves and ridge to allow free flow under the Ecoply, up the roof slope, and out. Roofing material suppliers should detail vent systems suited to their specific membrane or tile roofing. Proprietary ridge capping profiles or vents are available from roofing suppliers. Detail gaps of 25mm in the plywood at ridges, and at walls where a roof slopes up to an upper storey. For flat roofs, natural ventilation flows may be impeded. Use proprietary roof vents. Consider forced ventilation as appropriate.
31
3.3.4 Installation
Framing Frames should be at spacings to suit plywood thicknesses in Table 11. Additional requirements for roof and floor framing are: Ensure top edges of framing are properly aligned. Use dry Laserframe, hyJOIST or hySPAN framing to lower moisture level in roof spaces, second floor spaces, and reduce differential truss, rafter or joist deflections. Blocking (nogs, dwangs): Block all edges of standard square edge Ecoply Structural plywood. Block all edges at the ridge and gutter lines to prevent sag at capping or gutters. Block for high face loads or under areas accessed for maintenance. Blocking within the body of the roof or floor is not required for tongue and grooved edges, unless required for framing stability or the plywood is being used as a diaphragm to resist horizontal wind or earthquake loads. In this case fixings transfer shear across the joints and details should be specified on drawings. Use blocking on the flat to provide gaps where air flow is needed for ventilation. A specific membrane roofing supplier may require blocking.
ENDSHEET OVER AT LEAST TWO SPANS (SINGLE END SPANS SHOULD BE BLOCKED AT SHEET EDGES
NAIL OR SCREW AT CRS AS ON PAGE 33 BLOCKING AT GUTTER WITH VENT GAP AS REQUIRED
PLASTIC TONGUE OR T & G DOES NOT NORMALLY REQUIRE BLOCKING (SEE TEXT), EXCEPT WHEN USED AS A DIAPHRAGM
Sheet layout Ensure Ecoply sheets are dry before installation. Place face grain at right angles to supports. Sheets must be continuous over at least two spans (three framing members). Lay the sheets in a staggered pattern. Follow the recommendations in Allowing for moisture expansion of plywood under roof coverings. Allow sufficient clearance inside confining structure such as concrete or brick walls adjacent to the roof. Use extra allowances with large areas. Allow clearance for ventilation as required.
Fixing of sheets Ecoply may be fixed to different types of framing with nails or screws or a combination of fasteners and construction adhesives. See section 2.2, 2.3 and Figure 1. Fasteners should be corrosion resistant to a level appropriate to the end use, life expectancy (15 or 50 years) and expected exposure to moisture during construction and service. Galvanised fasteners are the minimum recommendation and are normally satisfactory in dry wood. Where Ecoply or framing may become damp or is H3 treated, use stainless steel screws or annular grooved nails for maximum durability. Follow the recommendations of the fastener manufacturer and membrane or floor covering supplier. The integrity of a plywood based floor or roof system is directly related to how well the panels are fixed to the framing. Ecoply must be fixed to resist wind suction loads, and to maintain surface qualities of the overlying roofing or covering. The minimum fastener specifications are in Table 6 and section 2.2. For roofing, check the additional requirements according to wind exposure. For high wind zones (over 44 m/s), very exposed sites, cyclonic conditions or roofs above 10 metres height, carry out specific structural design to the relevant standards. Screw fixing must be used for membrane roofing, and is preferred for all systems because of increased holding power and avoidance of head popping. Fixing to timber Ring shank nails or annular grooved nails or screws are recommended for additional holding power. For flooring, punch nails and apply floor sealant before filling holes with a suitable putty. For roofing, use flathead nails. Do not use jolt or bullet head nails. Stainless steel nails must be annular grooved. Ensure fastener is compatible with the roofing cover (consult roofing suppliers). Staples may be used provided that the withdrawal load is equivalent to the hand driven galvanised flathead nail. A suggested minimum is a 50mm long staple with 12mm crown and legs 1.8mm diameter. Space staples 20% closer than nails. Refer manufacturer for corrosion resistance and durability.
Fixing to steel: Fix directly to roll formed steel (up to 2mm thick) with self-drilling, self-tapping screws. If plywood gets damp and expands, screws in thicker steel may break. Keep Ecoply dry or use larger screws or; Bolt or screw battens to the steel and apply Ecoply as above for timber. Ensure that battens have adequate thickness for the minimum nail or screw length. Fastener Spacing for Wind Suction Wind pressure applies withdrawal loads to nails holding plywood to purlins and trusses. For the frame spacing in Table 11 designers may use the following guidelines for frame spacing up to 900mm throughout New Zealand for normal urban wind conditions. The main body of the roof 2.8mm nails spaced at 150mm centres on all cross framing. Roof edges All plywood at higher suction zones at the roof edges at gutters, eaves and gable ends must be supported on framing, and fixed at 100mm centres with 3.05mm diameter nails. Suction zones are interpreted from AS 1170 as being within 20% building length or width of a gable end, or gutter or ridge. Designers and builders should review site conditions to ensure adequate fixing is applied. Buildings in exposed sites and lee zones should be specifically designed using the loading standard (AS/NZS 1170) and the timber structures standard NZS 3603. In some wind conditions, the tiles themselves may be sucked from the plywood. Use a consulting engineer to assess site conditions, calculate wind pressures for the specific site, and determine the fastening and span requirements, and to check that the truss system can resist the loads being applied through the plywood. Fixing of roofing Fixing methods for tile, shingle and membrane systems must be designed for the expected wind and weather exposure to protect the Ecoply substrate. Some shingle systems may not be used in very high or cyclonic wind zones. Follow the specifications of the roofing manufacturer and refer to the appropriate BRANZ Appraisals.
33
PACKAGING
Packaging
35
Q: What should a specification for structural plywood include? A: A specification for structural plywood should include: Specification check list Quantity/size Thickness Edge finish Brand name Reference to Standard Stress grade /layup a Surface grade/bond type
*
Example 20 sheets of 2400x1200 12mm Square edge Ecoply structural plywood To AS/NZS 2269 F8 (12-24-5) CD A-Bond** EWPAA product certified*** Stress grades may vary between different manufacturers and products. ** Type A-bonds are suitable for permanent exposed applications and structural applications. *** The EWPAA JAS-ANZ Product Certification Mark certifies that Ecoply structural plywood products have been manufactured under a third party audited joint product certification programme to monitor compliance with AS/NZS 2269.
*
Accreditation
Q: What are F-grades? A: The stress grading system is a ranking system which utilises the symbol F and a suffix 8, 11, 14 etc as a code to apply a full suite of strength and stiffness properties to plywood products of that stress grade. For plywood of a given thickness, the higher the F-grade, the further it will span. For load bearing applications (e.g. flooring, roofing) the required F-grade as well as the plywood thickness must be specified to achieve the required span. F8 is the most common structural plywood grade found in New Zealand. All Ecoply structural products are F8 with the exception of 15mm Ecoply roofing which is F11 as standard and Ecoply Flooring which is available as F11 on request. Note, the standard Ecoply Flooring range is F8 for all thicknesses except 19mm (Longspan), which has higher stiffness for superior spanning capability. The F-grade is printed on the back of all Ecoply products in accordance with AS/NZS 2269. Q: What are surface/appearance grades (eg CD)? A: Appearance grades (eg BB, BD, CD, DD) denote the appearance grade of the plywood including the number and size of knot holes as defined in AS/NZS 2269 and summarised in Table 2 of this manual. The first letter describes the appearance of the face veneer and the second letter describes the back face. Q: How long can Ecoply be left exposed to the weather? A: Untreated Ecoply will maintain its structural integrity when exposed to the weather during construction for up to 3 months. The surface colour will start to silver off and surface checking cracks will become evident; where the finished appearance of the Ecoply is important, it should be protected during construction. Ecoply is also available H3 treated to resist decay or insect hazard. When used in accordance with this manual, it can be specified to meet the durability requirements of the New Zealand Building Code. Q: What treatment levels and types are used for Ecoply? A: Ecoply is available untreated or preservative treated. Ecoply is treated to the H3 hazard class for above ground use. The standard Ecoply treatment type is CCA (Copper Chrome Arsenate) although LOSP Azole (Liquid Organic Solvent Preservative) may also be specified where a clear treatment is required. LOSP Azole is the standard treatment type for BB, BD, Ecoply Grooved Lining and Shadowclad. CCA treatment gives the plywood sheets a green tinge and the drying process after CCA treatment may leave fillet marks on the face of the sheet. Q: Does Ecoply have to be treated when used as structural bracing? A: Ecoply used as bracing must be treated unless it is installed in an interior dry situation. Note, behind exterior cladding and in cavities (even if the Ecoply is covered with building wrap) are not considered to be an interior dry situation. Q: Do I have to re-treat cut edges of treated Ecoply? A: It is important to re-treat any cuts and holes with a brush on remedial treatment such as Metalex Clear End Seal. Q: What type of glue is used to manufacture Ecoply? A: Phenol formaldehyde (PF) resins are used to bond the plywood veneers. This forms a Type A (Marine) bond suitable for structural applications and exterior use. Phenol formaldehyde resins are dark red/brown in colour. Product details printed on the back of Ecoply sheets indicate the A Bond. Q: Does Ecoply emit formaldehyde? A: Formaldehyde occurs naturally in the environment and is emitted by processes such as combustion, decay and naturally by all timber species. It is present in the air we breathe at natural background levels of about 0.03 parts per million (ppm) and often up to 0.08ppm in outdoor urban air. The Japanese currently have the most stringent regulations which restrict emissions to 0.03ppm, equivalent to background levels. On-going testing and a recent survey of newly manufactured plywood and LvL products from EWPAA certified producers showed the average emission in laboratory conditions to be only 0.006ppm. This emission level is 5 times less than the naturally occurring background level of 0.03ppm. Q: How should Ecoply be installed to maximise its stiffness properties? A: Structural plywood has greatest stiffness along the long grain of the sheet (i.e. along its length). Therefore, flooring/roofing should be laid across joists/rafters rather than parallel to them.
37
Standards can be purchased online at www.standards.co.nz Building Code Compliance Documents can be downloaded free of charge at www.dbh.govt.nz
NOTES
39
As part of our ongoing commitment to the environment we have printed this brochure on FSC paper stock.
March 2009
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March 2009 Registered Trademarks of Car ter Holt Harvey Limited. Date of Publication March 2009 PJC 1515