Birch plywood grades explained: BB/CP and film-faced

Russian birch plywood is prized for its strength, stiffness and smooth, uniform face — but the grade codes (B, BB, CP, film-faced) trip up a lot of first-time buyers. Here is what they actually mean, and how to write a spec that gets you the right board the first time.

Face grades, from best to knotty

• B — the cleanest face: light, even colour, no open defects; occasional tiny sound pin knots. For visible, finished surfaces.
• BB — the workhorse: sound knots and oval patches ("boats") are allowed and neatly repaired. Smooth and paintable.
• CP — sound face with more colour variation and more repairs; small open defects permitted. For backs or painted work.
• C — the roughest: open knots and splits allowed. Strength is fine; looks are not. Usually a back or a hidden layer.

A sheet is graded on both sides, written face/back — so BB/BB, BB/CP, B/BB and so on. Pay for the good face only where it shows.

Glue & emission

Two things, often confused. Glue decides moisture resistance: WBP (weather- and boil-proof, phenolic) for exterior and humid use; interior glue for dry interiors only. Emission class decides formaldehyde release: E1 is the standard low-emission class for indoor use. Ask for both explicitly — "WBP, E1" — rather than assuming.

Film-faced plywood

For concrete formwork, the board is overlaid with a phenolic film, usually brown or black at 120-220 g/m². The film gives a smooth off-form finish and lets the panel be reused many times; edges are sealed to keep water out. Grades and stamp (and sometimes a logo print) are specified by the buyer.

How to write the spec

A clean birch plywood order names six things: face/back grade (e.g. BB/CP), glue & emission (WBP, E1), thickness (6.5-30 mm), format (1220×2440 or 1525×3050), surface (sanded or film-faced), and packing. Get those on paper and the board that arrives matches the board you priced.