NZ TIMBER EDITORIAL GUIDE
Plywood Types NZ
Plywood is a construction method - veneers bonded in alternating directions - not a single performance class. The first buying decision is whether the sheet has documented structural properties. Treatment, bond, face grade, thickness and end use come after that.
Start with structural status
| Need | Product family to investigate | Evidence to request |
|---|---|---|
| bracing, diaphragm, structural flooring or designed load | structural plywood | AS/NZS 2269 identification, stress grade and producer literature |
| lining, craft, temporary protection or appearance use without structural duty | non-structural plywood | producer intended-use and limitations |
| exterior or damp exposure | documented exterior-use system, sometimes H3.2 treated | treatment, bond, coating, edge and fixing requirements |
| permanent wet or ground contact | specialist design/product | explicit producer scope; ordinary plywood labels are insufficient |
A sheet can be H3.2 treated and still be non-structural. Conversely, structural plywood can be untreated and intended for protected dry use. Keep those axes separate.
Decode the stamp and listing
- Sheet dimensions: commonly expressed in millimetres, such as 2400 x 1200.
- Thickness: affects stiffness, fastener engagement and weight; it is not a structural specification by itself.
- Structural standard and stress grade: required where the sheet carries design loads.
- Treatment: indicates the preservative exposure class, not strength.
- Face/back grade: describes veneer appearance and allowable defects.
- Bond or exposure classification: must match the producer's intended conditions and finishing system.
Catalogue examples show why labels matter
Timber Dealers currently records structural untreated plywood references of $73 for 12 mm and $135 for 18 mm sheets, plus H3.2 structural 12 mm at $89. Separate H3.2 non-structural references are $49 at 9 mm, $59 at 12 mm and $114 at 18 mm. These checked reference fields are not live offers, but they demonstrate that thickness and treatment do not reveal structural status.
| Sheet label | Reference | What cannot be inferred |
|---|---|---|
| 12 mm structural untreated | $73/sheet | exterior suitability |
| 12 mm H3.2 structural | $89/sheet | a specific bracing rating without system data |
| 12 mm H3.2 non-structural | $59/sheet | permission to substitute into a structural use |
| 18 mm H3.2 non-structural | $114/sheet | greater structural suitability merely from thickness |
Match edges, fixings and finish to the system
Plywood performance depends on installed details. Panel orientation, support spacing, sheet expansion gaps, edge support, fastener type and spacing, coating and flashing belong to a documented system. Cut edges and drilled holes may need sealing or supplementary treatment exactly as the producer specifies.
- Name the end use and exposure.
- Confirm structural or non-structural status.
- Select thickness/stress grade from the design or system guide.
- Check treatment and bond for the exposure.
- Order compatible fixings, edge treatment and finish.
Face grades are an appearance contract
Plywood face classifications describe the quality of front and back veneers: repaired defects, knots, splits and surface suitability. They do not make a structural sheet stronger by appearance alone. A project may need both a structural grade and a selected face grade, especially where the panel remains visible.
Ask whether sheets are sanded, overlaid or textured, and whether patches are acceptable. Test coatings on the actual face because grain, fillers and sanding can absorb finish differently. If appearance is critical, agree which face is exposed and protect it during delivery.
- Structural lining: verify standard/grade first, appearance second.
- Cabinet or furniture work: consider purpose-made panel products and interior emissions/finish requirements.
- Temporary protection: confirm reuse, wet exposure and safe loading limitations.
- Exterior visible panel: use a complete documented cladding or lining system.
Sheet yield and offcut planning
A 2400 x 1200 sheet has a gross area of 2.88 m2, but framing centres, required edge support and cut layout determine useful yield. Rotating a structural sheet may conflict with face-grain direction. Create a panel layout from the design rather than dividing total wall area by 2.88.
Sources and technical guidance
- CodeHub - AS/NZS 2269.0 structural plywood (official)
- BRANZ Build - structural plywood (technical)
- Timber Dealers - plywood catalogue references (commercial)