Choosing the Right Species & Veneers for Strength
Concrete form panels must only be made from certain wood species and veneer grades to ensure they have sufficient strength to support the weight of the wet concrete. For full details check out APA’s Concrete Forming Design/Construction Guide and see specific product features below.
- The panels’ face and back require one of the strongest species: Group 1, 2 or 3, depending on bending strength and stiffness. Group 1 is the strongest.
- The choice of species is particularly important in non-overlaid plywood where the veneer is in direct contact with the concrete. Species such as Western Larch should be avoided because their high sugar content can prevent the concrete from setting. High sugar content is not a concern with HDO and special MDO plywood. The overlay on top of the face veneer means it is not in direct contact with the concrete.
- The lower the grade of veneer, the greater the size and number of defects which reduces its strength and stiffness.
Structural 1 Plyform Panels – B-B B-C HDO MDO
- APA Structural 1 Plyform requires grade B veneers for face and back, and both from the same species group. Face veneers must be at least grade B with the back not less than grade C.
- Face veneer and back veneers must be species group 1, grade B sanded.
- The minimum grade for cross band and centre inner veneers must be at least grade C and from group 1.
Class 1 Plyform Panels – B-B B-C HDO MDO
- Face veneer and back veneers require wood species group 1 excluding Western Larch.
- Face veneer must be a minimum grade B while the back veneer can be at least a grade C, both sanded.
- Cross band veneer can be species 1 or 2 . Grade C upwards.
- Centre veneer is the same grade but can be any species from 1 to 4.
Class 2 Plyform Panels – B-B B-C HDO MDO – option 1
- Face veneer and back veneers can be from wood species group 1 (excluding Western Larch) or group 2 – but both must be from the same group.
- Face veneer must be a minimum sanded B grade while the back veneer can be a sanded C grade.
- Centre and Centre veneers are C grade from any species from 1 to 4
Class 2 Plyform Panels – B-B B-C HDO MDO – option 2
- Cross band and centre veneers can be wood species 1-3, with wood species 4 also possible for the centre veneer. Both must be minimum C grade.
- The face and back veneers can both be from wood species group 3 upwards but Western Larch cannot be used.
- Both face and back sanded veneers must be a minimum 3.2mm (1/8”) thick before sanding, with the face requiring Grade B as a minimum while the back veneer can be grade C upwards.