What are the 4 grades of plywood?
The four standard appearance grades are A, B, C, and D — from cleanest face (A: knots up to 6 mm patched, no open defects, sanded) to roughest (D: large unrepaired knots, splits, broad variation; structurally sound but appearance-utility only). Faces and backs are graded separately and listed as a pair, e.g., "B-C" means B-grade face over C-grade back.
What are the 5 grades of plywood?
Some sources cite five grades by including E (élite or "premium A") above standard A grade, particularly in European EN 635 (E, I, II, III, IV) and Russian GOST (E, B, BB, CP, C) systems. In APA's North American system, the standard scale is four grades (A, B, C, D) with N-grade as a rare premium specifier-only grade above A.
What's the difference between CDX and ACX plywood?
CDX has a C-grade face, D-grade back, and Exposure 1 bond (waterproof glue, but rated only for construction-stage moisture). ACX has an A-grade face, C-grade back, and Exterior bond (rated for permanent outdoor service). ACX is roughly 2–3× the price of CDX and is the right specification when the panel face will remain visible outdoors; CDX is the workhorse for sheathing, subfloor, and other applications where the surface will be covered.
Is C-grade plywood waterproof?
C-grade describes the face appearance, not water resistance. C-grade panels can be Interior, Exposure 1, or Exterior bond — and only the bond determines moisture performance. CDX (C-grade face, D-grade back, Exposure 1 bond) handles construction-stage moisture; an Interior-bond C-grade panel would fail in damp conditions. Always read the bond classification, not just the face grade.
What grade is marine plywood?
Marine plywood is a separate construction with its own grading conventions. Standard marine plywood (BS 1088 in the UK / Commonwealth) has B-grade or higher faces, no voids in the inner plies (a critical structural requirement, distinct from face appearance), and waterproof phenolic bond. Marine grade should not be confused with simply "high-grade exterior plywood" — the void-free core construction is what makes it marine.
What plywood grade is best for cabinets?
For visible cabinet exteriors with clear or stain finishes: A-grade face. For paint-grade cabinet exteriors: B-grade face. For interior cabinet boxes and drawer sides where the face will be hidden: B-grade or C-grade is fine. The right grade is the cheapest one that meets the visible-finish requirement — over-specifying every cabinet panel as A wastes 30–50% on faces that will never be seen.
Does plywood grade affect strength?
No — grade describes appearance, not strength. A D-faced panel and a B-faced panel of the same construction (same number of plies, same species, same bond) have identical structural performance. Strength is governed by construction and bond, not face grade. Span ratings and stress grades are reported separately from appearance grades.
Why does CDX use a D-grade back?
CDX is engineered for sheathing, where the panel back faces the framing or cavity and is never seen. Using a D-grade back permits the mill to allocate cleaner C-grade veneers to the visible face while still meeting all structural requirements. The result is a structurally rated panel at a lower price than a C/C or B/C combination would deliver. This is also why CDX is the highest-volume APA-stamped panel produced in North America.
