Plywood specs look like alphabet soup: "CD F14 A-Bond", "BB interior", "BD structural". The confusion is that three completely separate rating systems get stacked into one line on the label. Once you know what each one measures, the code reads like plain English and you stop over-buying (or under-buying) for the job.
The three systems are: face and back veneer grades (how the surface looks), bond type (how well the glue survives moisture) and structural stress grade (how much load the sheet carries). They are independent — a sheet can have a beautiful A-grade face and a weak interior bond, or a rough C-grade face and a bomb-proof A-Bond glue line. Read all three before you buy.
Face and back veneer grades (A, B, C, D)
Veneer grades describe the appearance of the outer plies only — not strength, not glue. Under AS/NZS 2269 (structural) and AS/NZS 2270 (interior/decorative), each face is graded from A down to D:
| Grade | Appearance | Typical use |
|---|---|---|
| A | Near-flawless, sanded, paint or clear finish | Show faces, joinery, feature panels |
| B | Minor tight knots, small filled defects | Painted cabinetry, quality linings |
| C | Sound face, filled knots and splits allowed | Paint-grade, hidden faces, flooring |
| D | Open knots and gaps permitted, roughest | Structural where looks don't matter |
Plywood is graded on both sides, which is why you see two-letter combinations. The first letter is the face (the good side), the second is the back:
- AA — both sides premium; used when both faces show.
- BD — a clean B face with a D back; ideal when one side is on display and the other is hidden against a wall or frame.
- CD — the workhorse structural combination: a sound C face over a D back. You pay for strength and bond, not looks.
The first letter is the side you'll see, the second is the side you won't — pay for the face you actually look at, not both.
Bond type (A, B and C-Bond)
Bond type rates the glue line — how the veneers are stuck together and, critically, how that bond holds up to water and weather. This is the number one thing tradies get wrong, because it has nothing to do with the timber species or the face grade.
| Bond | Exposure it handles | Where it belongs |
|---|---|---|
| A-Bond | Permanent wet / full weather exposure | Marine, formply, exterior structural |
| B-Bond | Occasional wetting, protected exterior | Some structural sheathing |
| C-Bond | Dry, interior only | Furniture, linings, cabinetry |
A-Bond is a fully weatherproof phenolic glue line — the same bond used in marine plywood and form plywood. C-Bond is an interior-only glue that will delaminate if it gets repeatedly wet. Note that MR (moisture-resistant) MDF under AS/NZS 1859.2 is a related but separate product: "moisture resistant" means it copes with humidity and the odd splash, not that it can be soaked like A-Bond ply.
Structural stress grades (F8–F22)
The "F" grade is the structural rating under AS/NZS 2269 — it tells an engineer how stiff and strong the sheet is. The number is the characteristic bending stress in megapascals, so higher F means it carries more load over a given span:
- F8–F11 — lighter structural duties, general sheathing.
- F14 — the common all-rounder for structural flooring, walls and general building.
- F17 — form plywood and heavier load applications.
- F22 — high-strength bracing and engineered uses.
If a sheet carries an F-grade and the AS/NZS 2269 stamp, it's structural and can be used where an engineer or the NCC specifies a load rating. No F-grade means it's non-structural (AS/NZS 2270) — fine for a cabinet, not for a bearer or a braced wall.
No F-grade and no AS/NZS 2269 stamp means it's decorative — never put it anywhere the building relies on it to hold load.
Reading a full spec, and picking the right sheet
Put the three systems together and any label decodes cleanly. "Hoop Pine CD F14 A-Bond" means a C face over a D back (one usable side), F14 structural strength, with a fully weatherproof glue line — a classic structural flooring and general-building sheet. "Birch BB interior C-Bond" means two clean faces, no structural rating, dry use only — a cabinetmaker's panel.
RecommendedHoop Pine CD F14 StructuralShop → RecommendedBirch Plywood BDShop →Match the grade to the exposure and the loading, not to habit. Buying A-Bond marine for a dry wardrobe carcass is wasted money; buying a C-Bond interior panel for a bathroom or exterior soffit is a callback waiting to happen.
Quick decision order
- Bond first — will it ever get wet? That sets A, B or C-Bond and can't be fudged.
- Structural or not — does it carry load? If yes, you need an F-grade and the AS/NZS 2269 stamp.
- Face grade last — how good does the visible side need to look? Only then pay up for A or B.
- Three separate ratings hide in one label: veneer grade (looks), bond type (water), and F-grade (strength).
- Two-letter grades like CD or BD are face-then-back — pay for the side you'll actually see.
- A-Bond is weatherproof, C-Bond is dry-interior only; MR MDF resists humidity, not soaking.
- An F-grade plus the AS/NZS 2269 stamp means structural; no F-grade means decorative (AS/NZS 2270).
- Choose in order: bond, then structural rating, then face grade — it stops you over- or under-buying.