Is A-grade plywood always better than B-grade?

Not necessarily. If the face will be painted, B-grade (with minor repairs) is perfectly acceptable under primer and paint. If the face will be stained and visible, A-grade is worth the premium because imperfections show through stain. Match the grade to the application.

How do I check plywood core quality?

Look at the edge of the sheet. Count the plies (more is generally better in 18mm material — 7+ is good). Check for voids (dark gaps between plies). Press on the edge — a solid core feels firm; a voided core feels slightly springy. Ask the supplier for the core specification.

Can I use construction-grade plywood for cabinets?

Construction plywood (CDX, sheathing grade) has a rough face, voided core, and fewer plies. It is structurally adequate for utility shelving but not suitable for cabinet carcasses that need clean surfaces, reliable screw-holding, and consistent thickness. The cost savings are not worth the quality compromise.

Materials

Understanding Sheet Goods Grades

Updated July 25, 20263 min read

The short answer

Plywood grades (A, B, C, D) describe the quality of the face veneer — not the structural quality of the core. An A/AA grade means both faces are A quality. A B/BB core means the visible face is B grade and the hidden face is BB. For cabinetry, the face grade matters for appearance; the core quality matters for strength and screw-holding. Most cabinet-grade plywood is A or B face with a multi-ply void-free core.

Face grades

Face grades
Grade	Appearance	Repairs	Use
A	Smooth, clear, no defects	None or minimal	Visible surfaces: cabinet sides, shelves, drawer components
B	Sound, minor defects allowed	Small filler repairs	Semi-visible: cabinet backs, drawer boxes, secondary surfaces
C	Knots, patches, discoloration	Filled and sanded	Hidden surfaces: cabinet backs (if not visible), underlayment
D	Rough, significant defects	Extensive repairs	Structural only: subflooring, formwork, non-visible applications

What to look for beyond the grade letter

Core quality: The core is what gives plywood its strength. A void-free multi-ply core (7+ plies in 18mm) resists warping, holds screws better, and machines cleanly. A core with voids or fewer plies is weaker and less stable. Core quality is independent of face grade.
Veneer species: The face veneer determines appearance. Birch, maple and oak are common cabinet-grade faces. The species affects how the plywood takes stain, so match the face species to the desired finish.
Thickness consistency: Quality plywood is consistently 18mm (or the stated thickness) across the sheet. Cheap plywood varies, which creates problems during assembly. Check several points on the sheet with calipers.
Formaldehyde rating: CARB Phase 2 and E0 are the low-emission standards. For interior cabinetry in an occupied home, specifying low-emission plywood is a worthwhile investment in indoor air quality.
Layup orientation: The direction of the face grain affects appearance and how the sheet bends. For cabinet sides, the face grain typically runs vertically. For shelves, it runs across the span for maximum stiffness.

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Sheet goods by application

Cabinet carcass sides and top: 18mm cabinet-grade plywood, A or B face, multi-ply void-free core. This is the structural component — core quality matters more than face grade if it will not be visible.
Cabinet shelves: 18mm plywood, same specification as the carcass. For wider spans (over 600mm), consider 18mm plywood with a front edge lipping for additional sag resistance.
Cabinet backs: 6–12mm plywood (depending on whether it is visible). If the back is visible through a glass door or open shelf, upgrade to matching face grade. If hidden, C-grade is adequate.
Drawer boxes: 12–15mm plywood, B or C face. The drawer box is not visible when closed. Prioritise core quality for screw-holding at the joints.
Cabinet doors (painted): MDF — not plywood. For painted doors, MDF is the superior substrate. For stained doors, use solid wood or veneered plywood panels.

Answers

Frequently asked questions

Is A-grade plywood always better than B-grade?: Not necessarily. If the face will be painted, B-grade (with minor repairs) is perfectly acceptable under primer and paint. If the face will be stained and visible, A-grade is worth the premium because imperfections show through stain. Match the grade to the application.
How do I check plywood core quality?: Look at the edge of the sheet. Count the plies (more is generally better in 18mm material — 7+ is good). Check for voids (dark gaps between plies). Press on the edge — a solid core feels firm; a voided core feels slightly springy. Ask the supplier for the core specification.
Can I use construction-grade plywood for cabinets?: Construction plywood (CDX, sheathing grade) has a rough face, voided core, and fewer plies. It is structurally adequate for utility shelving but not suitable for cabinet carcasses that need clean surfaces, reliable screw-holding, and consistent thickness. The cost savings are not worth the quality compromise.

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