Unsanded, plywood sheathing panels are specially designed for walls and roof applications. (It can also be used for structural subfloor decking – but also see Builders Tips- 1 for the special flooring product Sturd-I-Floor). Other uses include shipping crates, pallets & pallet bins, shelving and partitions, as well as a range of industrial applications.
APA Rated sheathing panels are manufactured to meet PS 2-18 requirements. So long as mills comply with the main requirements, specifications can differ for their individual plywood. More on US standard PS2 and moisture requirements.
To be CE marked, US plywood must comply with the overall European plywood standard, EN 13986:2004+A1:2015. For applications such as roofing and walls, EN 13986 references specific standards for determining plywood panel performance characteristics for those applications. Find out here which individual standards apply – for instance, EN 314-2 for external bond classification.
Follow the trail below to learn more about sheathing, the importance of span ratings and the specific performance characteristics and EU standards that apply to roofing and walls. When you choose either the link for roofing or walls, the other link goes grey.
Essential:
Depending on specification:
APA’s system of span ratings denotes the maximum centre to centre spacing of supports (in inches) over which the plywood should be installed with its long dimension placed across the supports. This makes it easier to match the correct plywood panel to the specific spacing, whether studs in the wall construction, or the distance apart of the supports for normal domestic roof loadings.
When a panel is marked with one of two specific span ratings, Wall-16 or Wall-24, this tells you that it has been made specifically for use as wall sheathing. While all APA panels carry a span rating when suitable for roofing applications. This is not always the case for walls. Normal construction has the stud spacing of wall sections at either 16” (406mm) or 24” (610mm) centres. For wall sheathing use, panels with a roof span rating of 24 or greater may be installed vertically or horizontally as wall sheathing over studs spaced at 24” (610mm) on centre.
Those with roof span ratings of less than 24 may be installed vertically or horizontally over studs spaced at 16” (406mm) on centre. Where panels are fixed horizontally across studs, it will be necessary to block the unsupported paned edges between the studs.
For 3/8” (9mm) – usually 24/0 but Wall-16 or Wall-24 also possible.
For 7/16” (11mm) – usually 24/16 but also Wall-24.
Click here for more on plywood performance and thickness guidance.
The combined design live load plus dead load is 25 lbs/ft2 (1.195kN/m2).
Fixing should be placed 6” (150mm) apart around the panel edges and 12” (305mm) apart on intermediate supports.
Fixings should be positioned 3/8” (9mm) from the panel edges.
Plywood expands and shrinks slightly and when the panels are butted together tightly, the only way they can expand is to dish upwards or downwards. To allow for this, APA advises that a space of at least 1/8” (3mm) is left between panel edges. This may need to be increased if there is actual wetting of the panels.
Essential:
Depending on specification:
APA’s system of span ratings denotes the maximum centre to centre spacing of supports (in inches) over which the plywood should be installed with its long dimension placed across the supports. This makes it easier to match the correct plywood panel to the specific spacing, whether studs in the wall construction, or the distance apart of the supports for normal domestic roof loadings. All APA panels carry a span rating when they are suitable for roofing applications but this is not always the case for walls.
To enable the roof to carry the design load, you need to know the distance apart of three main roof sheathing supports. Knowing the span rating helps you match the panel to the distance between these supports. Supports placed too far apart will weaken the structure while those placed closer together can enhance the load that can be carried.
The span rating shown on the APA trademark indicates that the plywood panel can carry a uniformly distributed load of 50 lbs/ft2 (2.393kN/m2) domestic loadings.
APA trademarked panels will always show the specific span rating. It denotes this as a fraction, for example 32/16 for dual purpose panels suitable for both roofing and sub-flooring. The left-hand number is the relevant one – giving the centre to centre spacing of supports (eg 32 “) for roofing applications. (The right-hand number refers to sub-flooring applications).
The uniform deflection limit is L/180 (where L is the span) under a combined live load of 35 lbs/ft2 (1.676 kN/m2) plus a dead load of 15 lbs/ft2 (0.718 kN/m2) and L/240 under live load only. This represents one third of the load the panel has to pass to meet the requirements of PS2. These loadings assume the panel is laid continuously over two or more supports with the long dimension or strength axis across supports.
This will enable a higher uniformly distributed load to be accommodated. Recommended uniform live loads for APA Rated Sheathing can be found in Table 30 of the APA publication Engineered Wood Construction Guide (download here). It is advisable to check if other parts of the construction can also carry any increased load without any changes in design.
This will have several effects on the construction:
For 3/8” (9mm) – usually 24/0 but 20/0 also available.
For 15/32” (12mm) & ½” (12.5mm) - usually 32/16 but also 24/0.
For 19/32” (15mm) & 5/8” (16mm) – usually = 40/20 but also 32/16.
23/32” (18mm) & ¾” (19mm) – usually 48/24 but also 40/20.
Click here for more on plywood performance and thickness guidance.
For normal use, fixings should be placed 6” (150mm) apart around the panel edges and 12” (305mm) apart on intermediate supports. Fixing also should be positioned 3/8” (9mm) from the panel’s edges. Ring shank nails are recommended to prevent pull out under the effects of wind uplift.
In areas liable to high winds the distance apart needs to be moved closer. APA recommends spacing at 4” (100mm) intervals around the perimeter of the plywood and every 6” (150mm) at intermediate supports.
All plywood expands and shrinks slightly. When the panels are butted together tightly, the only way they can expand is to dish upwards or downwards. To allow for this, APA advises that a minimum space of 1/8” (3mm) is left between panel edges. This may need to be increased if there is actual wetting of the panels.
Download What’s New in FSC revised COC standard. Also, the previous FSC compulsory verification programme has been replaced by a due diligence protocol with a new risk assessment system. Learn more. North American good forestation practice supports the aims of EUTR. Its sustainably managed forests comply with one or more of the five leading certification agencies responsible for verifying proper forestry practices.
Learn how APA products can count towards a building’s BREEAM rating. The British Research Establishment and the US Underwriters Laboratories now recognize each other’s certified EPD making it simpler for APA member mills to gain environmental performance ratings under the BRE Environmental Assessment Method (BREEAM).
Under the harmonised European Standard for wood-based panels, EN 13986, Annex B, ‘wood-based panels glued with resins emitting either no formaldehyde or negligible amounts of formaldehyde after production as e.g. isocyanate or phenolic glue’ are to be classified as E1 (the lowest formaldehyde release class) without further testing.
See APA’s guide Formaldehyde and Engineered Wood Products. APA plywood is designated under the lowest E1 category for formaldehyde release without needing further testing. APA’s US PS 1 and PS 2 plywood have been tested to EN 717-1 and formaldehyde levels already meet the requirements for the E1 classification limit.
Also see: Formaldehyde (plywood) and Formaldehyde (OSB).
US plywood and OSB are equally effective as sturdy, robust and cost-effective solutions for non-construction applications – from shelving, site hoardings , protective linings in the cargo bay of delivery vehicles to packaging and furniture. See APA’s Performance Panels. Need help to decide what grade or type of panel to use for a specific application? APA’s Industrial Panel Selection Guide (Form T200) is another easy to use resource.
See APA’ s guide to Service Classes and Use Classes. For maximum biological durability, both Service Classes and Use Classes must be considered when specifying US CE-marked panels . This guide helps you make the right selection.
‘Hazard classes’ have been replaced (see updated EN 335:2013) by Use Classes covering plywood and OSB. They will also cover LVL when the LVL standards have completed their current update. Use Classes are based on different environmental exposures that can make the panel susceptible to deterioration. , as given in Eurocode 5, are used for assigning strength values and calculating deformation in load bearing situations. They are determined by the moisture content of the panel corresponding to the environmental humidity and temperature during service.
The British Research Establishment and the US Underwriters Laboratories now recognize each other’s certified EPD making it simpler for APA member mills to gain environmental performance ratings under the BRE Environmental Assessment Method (BREEAM). This is the UK’s leading and most widely used environmental assessment method for buildings and communities. It sets the standard for best practice in sustainable design and has become the de facto measure used to describe a building’s environmental performance. Learn how APA products can count towards a building’s BREEAM rating.
A good starting point is our Green Topics section and Types of EPD and the five life cycle stages
EN 15804:2012 +A1:2013 provides the core Product Category Rules (PCR) for the production of Environmental Product Declarations (EPD) for all construction products and services. Review with main environmental standards. For more details see: Core Product Category Rules (PCR) for Products and Services.
The European Union Timber Regulation (EUTR) puts specific obligations on operators and traders . Operators (or importers) are any (natural or legal) person first placing timber on the EU market. They must maintain records of any traders that they supply timber to. They must implement a due diligence system to minimise the risk of putting illegal timber or any of its derived products on the market. Learn more.
The European Union Timber Regulation (EUTR) puts specific obligations on operators and traders and applies to timber originating in the domestic (EU) market, as well as from third (non-EU) countries such as North America. The information it requires has to be retained for at least five years and be available on request. See European Timber Regulation.
Manufacturers of wood-based products covered by either a harmonised European standard (hEN) or a European Technical Assessment (ETA) must apply for CE marking under the 2013 Construction Products Regulation. See CPR & CE Marking and our Official Guidelines section.
This applies to ‘any product or kit which is produced and placed on the market for incorporation in a permanent manner in construction works or parts thereof and the performance of which has an effect on the performance of the construction works with respect to the basic requirements for construction works.’
Products must clearly display the CE mark and have the correct Declaration of Performance documentation. For more info: CPR & CE Marking.
Under the CPR, manufacturers wishing to trade in the European market are legally required to set down the levels of performance for any construction product. They have to be listed in an official document called a Declaration of Performance.
Exposure 1 is a glue bond classification. It uses the same 100% waterproof glue as exterior panels and refers to a panel’s durability when long delays in construction are expected or when facing high moisture content. For plywood, see https://apawood-europe.org/products-trademarks/plywood/trademarks/glue-bond/. For OSB: https://apawood-europe.org/products-trademarks/osb/trademarks/exposure-durability-classification/
Structural 1 refers to a panel’s superior performance characteristics. For OSB, see https://apawood-europe.org/products-trademarks/osb/comparable-performance-requirements/
For Structural 1 plywood, all panels have special improved veneer grades and if manufactured to the American PS1 standard, the veneer grades will be species with a Group 1 strength classification. See group classification of species.
Plywood Design Information looks at the plywood grades A-A, A-B, A-C; B-B, B-C; C-C, C-D and the relevant standards that the trademarked panels comply with.
For plywood, see Span rating. For OSB, see Span rating. A full range of technical information in under Products and Trademarks.
OSB Structural I on an APA trademark indicates that the OSB structural-panel meets the requirements of a Performance Rated panel. This delivers superior design capacity for these panels over OSB Rated Sheathing and Sturd-I-Floor. Also see Comparison of Superior Design Capacities for OSB Structural I Sheathing with OSB Rated Sheathing.
Veneer in a finished US trademarked plywood panel must conform to one of the six grades listed in the US PS 1-09 standard: N, the highest classification (rarely produced), followed by A, B, C-plugged, C and D. Non-overlaid APA plywood panels come in three levels of surface finish – sanded, touch-sanded and unsanded.
Also see veneer grades for Popular APA Plywood Panels.
APA has produced two easy to follow guides to help match the grade numbers given on a US finished plywood panel with the requirements of EN 635-3.
Detailed guide listing permissible defects – with maximum sizes.
Simplified guide to the US PS 1-09 veneer grading rules and appearance grades in EN 635-3 based on the appearance of the surface veneers. Equivalents cannot be exactly compared as two different sets of grading rules apply.
See APA’s comprehensive Concrete Forming Design/Construction Guide for architects, engineers and contractors and the types of APA concrete forming plywood panels.
APA panels have a tongue and groove profile on their two long edges. This eliminates the need for support (blocking) under adjacent panel edges to prevent them from deflecting independently of each other when load is applied. See Tongue & Groove (plywood) and Tongue & Groove (OSB).
‘Sized for Spacing’ on APA Rated Sheathing, APA Rated Sturd-I-Floor and APA Rated Siding trademarks indicates that the manufacturer has produced the panel to a size slightly less than the traditional nominal 2440mm (96″) by 1220mm (48″). It is done to facilitate proper panel spacing during construction. See Sized for Spacing (plywood) and Sized for Spacing (OSB). For further technical details see Product and Trademarks.
Performance Category, Panel Thickness and Span Ratings are key categories that need to be considered together. See Thickness, Performance Category (plywood) and Thickness, Performance Category (OSB).
Plywood: Span rating
OSB: Span rating
Span Rating denotes the maximum recommended centre to centre spacing of supports in inches over which the panel should be placed with its strength axis across two or more supports. Plywood: Span rating. OSB: Span rating
Bond classification relates to moisture resistance of the glue bond and therefore to the structural integrity of the panel. See glue bond durability classification (plywood) and exposure durability (OSB).
See APA’s guide to panel grades and also info on understanding the trademark.
See APA’s guide to ‘Plywood Panel Grades for Specific Applications’
The main standards are: EN 13986 and EN 300. But also see the other relevant standards for OSB.
The main standards are: EN 13986, EN 636, EN 314, EN 635-3. And for more details, see EU standards for plywood.