Section Contents

Glue Bond Durability Classification

APA trademarked panels are produced in two bond classifications, Exterior and Exposure 1, both meeting the performance requirements of EN 314: Plywood – Bond quality.

  • 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 do 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.

The bond classification relates to moisture resistance of the glue bond and performance requirements are based on the moisture resistance of the panel. 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.

Since the aesthetic (non-structural) attributes of panels may sometimes be compromised by exposure to weather, APA provides detailed installation recommendations.

Glue bond classifications of popular grades of APA plywood in relation to specific EU standards

 Popular APA PlywoodPanel Grades

Bond Durability Classification

Applicable End Use
Service Conditions According to European Standard EN 6366

US Product Standards
PS11, PS 22
&
APA Performance Standard PRP- 1083

European Standard
EN 314-14
&
EN 314-25

C-D (CDX)

Exposure 17

2

EN 636-1 (dry)
EN 636-2 (humid)

C-C (CCX)

Exterior8

3

EN 636-1 (dry)
EN 636-2 (humid)
EN 636-3 (exterior)9,10

A-C (ACX)

Exterior8

3

EN 636-1 (dry)
EN 636-2 (humid)
EN 636-3 (exterior)9,10

B-C (BCX)

Exterior8

3

EN  636-1 (dry)
EN  636-2 (humid)
EN 636-3 (exterior)9,10

Sturd-I-Floor

Exposure 17

2

EN 636-1 (dry)
EN 636-2 (humid)

Exterior8

3

EN 636-1 (dry)
EN 636-2 (humid)
EN 636-3 (exterior)9,10

C-D plugged

Exposure 17

2

EN  636-1 (dry)
EN 636-2 (humid)

C-C plugged

Exterior8

3

EN 636-1 (dry)
EN  636-2 (humid)
EN 636-3 (exterior)9,10

Notes:1.US PS1 : Product Standard 1 – Structural Plywood
2.US PS2 : Product Standard 2 – Performance Standard for Wood-based Structural-Use Panels
3.APA PRP 108  : Performance Standards and Qualification Policy for Structural-Use Panels
4.EN 314-1    : Plywood – Bonding quality – Test methods
5.EN 314-2    : Plywood – Bond Quality – Requirements
6.EN 636       : Plywood specifications
7.Exposure 1 : Have the same glue line as Exterior Panels, but with some restrictions on exposure time due to veneer grade lay-up.
8.Exterior: Adhesives capable of immersion in boiling water for 72 hours (minimum veneer grade C in panel lay-up).
9.EN  636-3:  Corresponds to a Use Class 3 (exterior, above ground not covered) in EN 335-3– Durability of wood and wood-based products – Definitions of hazard classes of biological attack – Application to wood-based panels.  It refers to plywood that is capable of withstanding exposure to weathering conditions and liquid water or water vapour in a damp but ventilated location.
10.Biological durability needs to be considered when designating plywood for exterior use.  If the species are not naturally durable and the plywood is liable to remain wet (20% M.C. or greater) for long periods then suitable preservative treatment is strongly advised to combat any likelihood of attack from biological agencies.