What does CDX plywood mean?

CDX stands for C-face, D-back, X (exposure) glue. It's the most common construction plywood grade. The C face has tight knots up to 1-1/2 inches and some defects. The D back has larger knots and knotholes. The X means the plywood is made with exterior-rated glue that resists moisture. However, CDX is NOT rated for permanent exterior exposure — it's designed for temporary exposure during construction. CDX is used for roof sheathing, wall sheathing, and subflooring. It's the cheapest plywood grade available, typically $25-$40 for a 1/2-inch sheet. What is Baltic birch plywood used for?

What is Baltic birch plywood used for?

Baltic birch plywood is used for cabinet drawer boxes, woodworking jigs and fixtures, CNC projects, high-end furniture, and any application requiring a void-free core with excellent edge quality. It has more layers than standard plywood (13 layers in 3/4 inch vs 7 in standard), providing superior screw-holding strength, edge stability, and consistency. Baltic birch is sold in 5-foot by 5-foot sheets (not 4x8) and costs $60-$100 per sheet for 3/4 inch. It's the preferred plywood for fine woodworking where exposed plywood edges are part of the design. What is the difference between marine plywood and regular plywood?

What is the difference between marine plywood and regular plywood?

Marine plywood has a void-free core (no gaps, knotholes, or voids in any layer) and A-A or A-B face quality with waterproof adhesive. Regular construction plywood (CDX) has voids in the core, lower-quality face veneers, and while it uses moisture-resistant glue, it's not rated for continuous water exposure. Marine plywood does NOT contain special waterproofing treatment — the wood itself is no more waterproof than regular plywood. The advantage is structural: the void-free core maintains strength even if the wood gets wet, whereas voids in regular plywood create weak points. Marine plywood costs $80-$200 per sheet vs $25-$60 for CDX.

Article

Woodworking & Lumber

Plywood Grades Explained: A, B, C, D & Specialty Panels

Lumberama Editorial Team, Sheet Goods & Panel Product Specialists Apr 14, 2025 10 min read

How Plywood Grading Works

Plywood grades use a two-letter system indicating the quality of the front (face) and back veneer. The first letter is the face; the second is the back. A-C plywood has an "A" quality face and a "C" quality back. The core (inner layers) is not described by this grading system.

Softwood plywood (construction plywood made from Douglas fir, southern pine, or spruce) uses the PS 1 standard published by the American Plywood Association (APA). Hardwood plywood (oak, birch, maple face veneers) uses the ANSI/HPVA HP-1 standard with slightly different grade names (A, B, C, D, E).

Veneer Grades (Softwood Plywood)

A grade (highest): Smooth, paintable face. Neatly made repairs permitted. The surface is sanded smooth with no open defects. Suitable for high-quality painted surfaces and applications where appearance matters. A-grade veneer is the most expensive face option.

B grade: Solid surface with circular repair plugs ("football" patches), tight knots up to 1 inch, and minor splits permitted. Sanded smooth. Suitable for painting and applications where some patched defects are acceptable. B-grade is common as a back face on A-B panels.

C grade: Tight knots up to 1-1/2 inches, knotholes up to 1 inch, some splits, and repairs permitted. Not sanded. Suitable for sheathing and structural applications where appearance doesn't matter. C-grade is the minimum face quality for exterior-rated plywood.

C-Plugged: An improved C grade with knotholes and splits limited in size and repaired. Better than C but not as smooth as B. Used as the face of underlayment-grade plywood.

D grade (lowest): Knots and knotholes up to 2-1/2 inches. Splits, repairs, and other defects permitted. Used only for interior applications (sheathing, subflooring) where the surface is hidden. D-grade is not permitted in exterior-rated plywood.

Common Construction Plywood

CDX: The most common construction plywood. C face, D back, X indicates exposure durability (exterior glue). Despite the "X," CDX is NOT rated for permanent exterior exposure — it's rated for temporary exposure during construction. CDX is used for roof sheathing, wall sheathing, and subflooring. It's the cheapest plywood grade. 1/2" CDX: $25-$40/sheet; 3/4" CDX: $40-$60/sheet.

BCX: B face, C back, exterior glue. A step up from CDX with a smoother face. Used when one side is visible (utility shelving, shop cabinets, garage projects). More expensive than CDX but cheaper than hardwood plywood.

ACX: A face, C back, exterior glue. Premium construction plywood with a smooth, paintable face. Used for soffits, visible exterior panels, and painted applications. One of the more expensive softwood plywood grades.

Underlayment: C-Plugged face, D back. Designed to go over subflooring as a smooth base for vinyl, tile, or carpet. The plugged face provides a smoother surface than standard CDX.

Specialty Plywood

Marine plywood: A-A or A-B face quality with NO voids in the core layers. Uses waterproof adhesive and has no gaps, knotholes, or voids anywhere in the panel. Marine plywood does NOT contain any special waterproofing treatment — the wood itself is no more waterproof than regular plywood. The distinction is the void-free core and high-quality face veneers. Used for boat building and applications where structural integrity in wet conditions is critical. Expensive: $80-$200/sheet for 1/2" to 3/4".

Baltic birch plywood: Imported from Russia, Finland, and the Baltic states. Made entirely from birch veneers (face, back, and core). More layers than standard plywood (13 layers in 3/4" vs. 7 layers in standard). Void-free core. Consistent quality. Superior screw-holding and edge quality. The standard for cabinet drawer boxes, jigs, fixtures, and CNC projects. Sold in 5' x 5' sheets (not 4' x 8'). 3/4" Baltic birch: $60-$100/sheet.

Hardwood plywood: Plywood with decorative hardwood face veneers: oak, maple, birch, walnut, cherry. Used for cabinetry, furniture, and architectural panels. Hardwood plywood typically has a veneer core (all-wood layers), MDF core (smooth, flat, heavy), or combination core. MDF core hardwood plywood is flattest and paints best but is heavy. Veneer core is lighter and stronger. Prices: $50-$150/sheet depending on species and core type.

Sanded plywood (shop-grade): A-B or B-B plywood sanded smooth on both faces. Made from softwood (usually fir or pine). Used for shelving, shop furniture, and projects where a smooth, paintable surface is needed without the cost of hardwood plywood. A good middle ground between rough CDX and expensive hardwood plywood.