Section Contents

Understanding APA Plywood Trademarks



Edge mark may be used when panel has two sanded/good faces

Explaining panel terminology

Panel Grade

There are two methods used to identify APA plywood panels:

  • Type of veneer grade identified on the face and back of the panel e.g. A-C or B-B.
  • Identification of panel’s end use application e.g. Rated Sturd-I-Floor, Rated Sheathing, Rated Siding (cladding) or Underlayment.

Bond Classification

APA trademarked panels may be produced in two bond classifications – Exterior and Exposure 1.  The bond classification relates to moisture resistance of the glue bond.  Since aesthetics (non-structural) attributes of panels may be compromised to some degree by exposure to weather, APA installation recommendations are designed to provide optimum overall performance.

Glue Bond durability classification of the panel does not relate to fungal decay resistance of the panel.  Fungal decay of wood products may occur when the moisture content exceeds 20 percent for an extended period.

  • Exterior: Adhesive bond capable of withstanding repeated wetting and re-dying or long-term exposure to weather or other conditions of similar severity.  This is a Bond Class 3 glue line according to EN 314-2.
  • Exposure 1: Panels suitable for uses which does not involve long-term exposure to weather.  Panels classified as Exposure 1 are intended to resist the effects of moisture due to construction delays or other conditions of similar severity.  Exposure 1 panels are made with the same exterior adhesive used in Exterior panels.  However, because other panel compositional factors may affect bond performance only exterior panels should be used for long-term exposure to weather.  Exposure 1 is equivalent to a Bond Class 2 glue line according to EN 314-2.

Span Rating

This 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. The span rating can be displayed in one of two ways:

  • Single number for wall (Wall-24) and floor (24 o.c.) applications
  • Fractional format where the panel is suitable for both roofing and subflooring uses such as rated sheathing 32/16 (where the left hand number represents the maximum centre to centre spacing of supports for use in roofing and the right hand number covers the maximum centre to centre spacing for subflooring applications).
  • An exception to this rule is 303 Siding (cladding) and wall only panels where span rating applies when the panels are installed vertically.

Overview of the relationship between Span Ratings, Performance Category and Panel Thickness.

Group Number

A term used to classify the species used to manufacture the plywood panel’s face and back under US Product Standard PS1 – Structural Plywood.  Suitable species are classified into 5 groups based on their bending strength and stiffness.  Group 1 species are the strongest and Group 5 species being the weakest.

Thickness and Performance Category

Thickness and Performance Category on the panel need to be viewed together, with Span Rating info.

  • Thickness always has to be within the minimum and maximum thickness specification for the designated Performance Category.
  • The thickness of plywood panels is shown as a decimal figure (0.451 IN.) in inches.
  • Performance Category is linked to the nominal panel thickness e.g. 15/32 CATEGORY.
  • Both the thickness and the performance category are displayed as separate items on the panel.  See also Performance Category.

Sized for Spacing

The words ‘SIZED FOR SPACING’ is often found on APA Rated Sheathing, APA Rated Sturd-I-Floor and APA Rated Siding trademarks indicating that the manufacturer has produced the panel to a size slightly less than the traditional nominal 2440mm (96″) by 1220mm (48″).  This is done to facilitate proper panel spacing during construction.  The use of this notation is not a manufacturing requirement but is sometimes added as a courtesy to the customer.

Spacing between ends and edges of adjacent panels helps prevent buckling due to panel expansion caused by moisture absorption.  The recommended spacing between panels is 3mm (1/8″) at both the end and edge joints, unless otherwise recommended by the manufacturer.

Tongue-and-Groove (T&G)

This indicates that the APA panel has a tongue and groove profile on its two long edges which is to an APA approved pattern.  This eliminates the need for support (blocking) under adjacent panel edges to prevent them from deflecting independently of each another when load is applied. The material removed to create the tongue normally reduces the width of the panel by 12.5 mm (1/2″), therefore the net width of tongue and groove panels is typically 1206mm (47-½”).

US Standards

APA plywood is manufactured to two US standards:

  • PS 1-09 US Voluntary Product Standard, structural plywood
  • PS 2-10 US Voluntary Product Standard – the performance standard for wood-based structural-use panels

The last two digits of the US product standard number indicate the year in which the standard was most recently approved.

Performance Rated Panel Standard

This shows that the panel was manufactured to meet the performance requirements of APA’s Performance-Rated Panel Standard PRP 108.  Performance standards do not prescribe by what means the panel is produced but the objective is to assure that the panel will satisfy the requirements for a particular end use application.  This is similar to the performance-based approach taken by European Standards.

Concrete Form Panel Class

There are three classes for concrete form panels:

  • Class 1 Plyform: Group 1 faces for high strength and stiffness
  • Class 2 Plyform: May have Group 2 faces but still provides adequate strength for most forming applications
  • Structural 1 Plyform: Species Group 1 with minimum B grade veneers face and back gives greater strength than Class 1

The classification is based on the grade of veneer used for the panel faces in combination with that used for the inner plies.

303 Siding Grades

This is only applicable to panels specifically manufactured as APA 303 Rating Siding.  These are panels used for cladding the outside of a variety of building types from domestic dwellings to garden sheds. The 303 Siding Grade indicates the number and type of repairs on the face of APA 303 Siding (external cladding) e.g. 303-6-S/W.

303 APA’s siding manufacturing specification
-6- maximum number of repairs allowed on the face of a 2440mm (96″) by 1220mm (48″) panel. The allowable number of repairs is proportional for other sizes
S/W indicates the type of material used for the repair
‘S’ synthetic repair

Mill Number

This refers to the APA code number awarded to each producing mill.