The five questions that pick your plywood
Walk into a plywood yard and you'll find marine, structural, formply, hoop pine, birch, OSB and a dozen face grades — often at similar-looking prices. The trick isn't memorising every product. It's answering five plain questions about your job, in order. Get through them and you've usually narrowed the whole range to one or two boards.
- What are you building?
- How much water and weather will it see?
- Does it carry load?
- What finish do you need?
- What size — and can you handle it?
Work them top to bottom. Each answer rules out boards the next question would otherwise leave on the table.
1. What are you actually building?
Start with the end use, because it sets the standard the board has to meet. Structural jobs — flooring, bracing, beams, formwork, anything that holds a building up — are covered by AS/NZS 2269 and carry a stress grade (the F-rating). Non-structural and interior work — cabinets, linings, shelving, decorative panels — sits under AS/NZS 2270, where appearance matters more than raw strength. Sheet products such as moisture-resistant MDF for wet-area lining fall under AS/NZS 1859.2.
Naming the job first stops you over-buying (a marine board in a wardrobe) or under-buying (an interior panel on an exposed deck).
2. How much water and weather will it see?
Moisture is what kills plywood, and it's controlled by the glue line, not the timber. That's the bond type. A-Bond is a fully weatherproof phenolic glue that won't let go, even under permanent water. B-Bond handles occasional wetting. C- and D-Bond are interior glues for dry, protected spaces. Match the bond to the wettest moment the board will ever see — not the average day.
| Where it lives | Look for | Bond |
|---|---|---|
| Constant water (boats, wet decks) | Marine plywood | A-Bond |
| Outdoors, weather-exposed | Exterior structural | A-Bond |
| Concrete formwork | Formply / film face | A-Bond |
| Wet areas (bathroom, laundry lining) | MR MDF / wet-area VJ | Moisture resistant |
| Structural, dry (walls, subfloor) | F-rated structural | A/B-Bond |
| Interior joinery & panelling | Non-structural, good face | C/D-Bond |
When water is in doubt, buy up a bond — an A-Bond sheet in a dry room is never wrong, but a C-Bond sheet outdoors always fails.
For anything in constant contact with water — boats, pontoons, permanently damp zones — a true marine board is the safe call.
RecommendedMarine Plywood BS1088Shop →3. Does it carry load?
If the answer is yes, you need a structural board to AS/NZS 2269 with the right stress grade. The F-rating (F8, F11, F14, F17, F22 and up) tells you stiffness and strength — the higher the number, the stiffer the board. Match it to the span and load in your engineer's spec or the manufacturer's span tables; don't guess. Wall bracing, subfloors and formwork each have purpose-made structural boards, so pick the one built for the job rather than a generic sheet.
Hoop pine CD is the workhorse here — a clean-enough face over a genuine structural core, at home in flooring, wall sheeting and general framing.
RecommendedHoop Pine CD F14 StructuralShop →If it doesn't carry load — a bookshelf, a cabinet carcass, a decorative panel — you can drop to a non-structural board and put the saving into a better face.
4. What finish do you need?
Plywood faces are graded by appearance, usually a two-letter code (such as A, B, C, D or S) for the front and back veneers. An A face is near-flawless and ready for paint or a clear coat; C and D faces are rougher, with patches and knots, and belong where nobody looks. Decide which faces will actually show:
- Seen and clear-finished — birch or a high face grade; smooth, tight, and takes a clear coat cleanly.
- Seen and painted — a good paint-grade face; a little filling is fine.
- Hidden — a C/D face saves money with no downside.
Pre-grooved panels (V-groove, VJ) are the shortcut when the finish is the feature — the profile is already milled in, ready to line a wall straight off the sheet.
5. What size — and can you handle it?
Standard sheets are 2400 × 1200, but plywood also runs to oversized lengths and a range of thicknesses, and a full 18mm sheet is heavy and awkward for one person. Two things to settle before you order:
- Thickness follows from the load and span (structural) or the look and rigidity you want (non-structural).
- Sheet size and cutting — buying cut-to-size means less waste, less lifting, and panels that actually fit through the door.
This is where the earlier answers pay off. Once you know use, bond, grade, finish and size, matching them to a specific product is quick — and if you'd rather not hold all five in your head, that's the same logic a good on-site plywood finder walks you through. Same five questions, less standing in the aisle.
- Answer the five questions in order — use, moisture, load, finish, size — and the range narrows itself.
- Bond type (A/B/C) is about water, not strength; match it to the wettest moment the board will face.
- Structural means AS/NZS 2269 with an F-rating; interior work is AS/NZS 2270; moisture-resistant MDF lining is AS/NZS 1859.2.
- Only pay for a premium face where it will be seen — hide a C/D grade everywhere else.
- Sort thickness and sheet size up front, and cut-to-size to save waste, weight and hassle.