Plywood Basics: Types, Grades and What to Use Where

Plywood is an engineered wood panel made of thin veneer layers glued with the grain rotated 90 degrees between plies — cross-graining that makes it stronger and more stable than solid lumber of the same thickness, except when a void-filled core or an off-grade face cancels that advantage out. The wrong grade wastes money on a hidden subfloor or fails a visible cabinet door. This guide covers plywood grades A through D plus CDX, the main core types, and which one fits sheathing, cabinetry, or outdoor builds.

What Is Plywood, and How Is It Made?

Plywood is an engineered wood panel built from an odd number of thin wood veneers — usually 3, 5, or 7 — glued together with each layer’s grain running perpendicular to the one below it. That cross-graining, sometimes called cross-lamination, spreads stress across two directions instead of one, which is why a plywood panel resists warping, splitting, and shrinking better than a solid board of the same thickness.

Manufacturers press the glued veneer stack under heat, which cures the adhesive and bonds the plies into a single rigid sheet. The number of plies, the species used for the face veneer, and the type of glue all determine what the finished sheet is rated for — interior furniture, structural framing, or continuous outdoor exposure.

What Are the Layers of Plywood Called?

Each individual sheet of wood in a plywood panel is called a ply or a veneer. The outermost ply on the good-looking side is the face veneer, the opposite outer ply is the back veneer, and everything sandwiched between them is the core.

Plywood Grades Explained: A, B, C, D, and CDX

Plywood is graded by veneer quality on a letter scale from A (smooth, sanded, virtually defect-free) to D (visible knots, patches, and open splits). Every sheet carries two letters — the face grade first, the back grade second — so A-C plywood has a premium face and a rougher, hidden back, while B-D has a good face over a rough back meant to be covered.

Grade	Surface Quality	Typical Use
A	Sanded smooth, no knots or patches	Cabinet doors, furniture faces, built-ins
B	Solid surface, minor repaired knots	Painted furniture, secondary cabinet surfaces
C	Knots and knotholes up to 1½ inches allowed	Sheathing faces, subfloor where it won’t show
D	Rough, largest allowed knots and splits	Hidden backs, sheathing that stays covered
CDX	C-face, D-back, exterior glue (X)	Roof decking, wall sheathing, subfloor

The trailing “X” in a grade like CDX doesn’t describe the veneer — it describes the glue. An X rating means the panel uses exterior-rated adhesive that survives job-site moisture during construction, not permanent outdoor exposure. For a deck, fence, or anything that stays wet long-term, that distinction matters enough to compare against a true exterior or marine-rated panel before buying; our CDX plywood vs. OSB comparison breaks down where CDX’s moisture rating actually holds up.

Types of Plywood by Core and Species

Grade describes surface quality; type describes what the plywood is made from and what it’s rated to withstand. The four types below cover most projects a home shop or job site will run into.

• Softwood plywood — Made from pine, fir, or spruce veneers. The default choice for framing, sheathing, and subfloor because it’s strong relative to cost, not because it looks good.
• Hardwood plywood — Faced with oak, birch, or maple veneer over a often-softwood core. Used wherever the surface will be visible and finished: cabinetry, furniture, shelving.
• Baltic birch plywood — A void-free, all-birch-veneer panel with far more plies per inch than standard hardwood plywood, giving it clean, layered edges that don’t need banding. Common in jigs, drawer boxes, and furniture where the edge itself is part of the design.
• Marine plywood — Built with void-free core stock and fully waterproof adhesive, rated for continuous water contact. Costs several times more than CDX and is overkill for anything that isn’t a boat hull, dock, or permanently wet application.

Plywood vs. OSB vs. MDF: Which Should You Use?

All three are engineered wood panels, but they’re made differently and aren’t interchangeable. Plywood glues cross-grained veneer sheets, OSB (oriented strand board) presses and bonds wood strands with wax and resin, and MDF (medium-density fiberboard) compresses wood fibers into a dense, uniform panel with no visible grain at all.

Material	Strength	Moisture Resistance	Best For
Plywood	High, especially screw-holding	Good with exterior glue; not waterproof	Subfloor, sheathing, cabinetry
OSB	High for load-bearing spans	Swells more than plywood if it gets wet	Wall and roof sheathing on a budget
MDF	Lower, poor screw-holding at edges	Poor — swells and crumbles when wet	Painted interior trim, indoor furniture

For a like-for-like structural swap, our CDX plywood vs. OSB guide goes deeper on span ratings and job-site handling for each.

Standard Plywood Sizes, Thicknesses, and Prices

Nearly every big-box store and lumberyard stocks plywood in full 4×8-foot (48 x 96-inch) sheets, in 1/4-inch, 1/2-inch, and 3/4-inch thicknesses as the three most common options. Thinner 1/8-inch and 3/8-inch sheets exist for cabinet backs and underlayment, and specialty suppliers carry 5×5 Baltic birch sheets for shops that don’t need a full 4×8 panel.

Price scales with both thickness and face grade, not just size. A 3/4-inch sanded hardwood-faced sheet costs several times more per square foot than a 7/16-inch OSB sheathing panel of the same footprint. For current per-sheet pricing by grade and thickness, see our breakdowns of Lowe’s 4×8 plywood prices and Home Depot plywood costs.

Choosing the Right Plywood for Your Project

Match the grade and type to what the surface needs to do, not just what’s cheapest on the shelf. These four project categories cover most of what plywood gets used for:

1. Furniture construction: A-grade hardwood plywood with a smooth, sanded face resists warping and finishes cleanly.
2. Cabinetry: Cabinet-grade plywood, usually A or B face, holds up to repeated door and drawer use without telegraphing seams through paint.
3. Home construction: Structural-grade CDX or OSB-rated sheathing meets the span and load requirements for walls, roofs, and subfloors.
4. Decorative projects: Hardwood or Baltic birch plywood with an attractive face veneer works for paneling, open shelving, and exposed-edge furniture.

Working With Plywood: Cutting, Joining, and Finishing

Cutting and Sizing Plywood

Score the cutline with a utility knife before sawing to sever the face veneer’s fibers and stop tearout, then run a high-tooth-count blade — 100 teeth or more on a 7-1/4-inch blade — for any cut that will stay visible. Support the full sheet on scrap lumber so the offcut can’t sag and pinch the blade mid-cut.

Joining Plywood

Joining plywood panels with a butt, dado, or rabbet joint adds both strength and a cleaner look than edge-gluing alone. Apply glue evenly across the full joint face, clamp until cured, then sand the seam flush before finishing.

Protective Coatings and Finishes

Exterior or high-moisture plywood needs a sealant — polyurethane or a dedicated waterproofing finish — to keep water out of the exposed edge grain, which is where plywood absorbs moisture fastest and starts to delaminate. Indoor furniture-grade plywood just needs a varnish or paint suited to the face veneer species.

Storing and Maintaining Plywood

Store sheets flat or fully vertical on edge with even support — leaning a sheet at an angle for weeks lets it sag permanently. Keep plywood off a concrete floor (moisture wicks up through concrete) and out of direct sun, and inspect edges periodically for the telltale separation lines that signal delamination has started.

Frequently Asked Questions

What are the different grades of plywood?

Plywood is graded A through D by face and back veneer quality, with A being smooth and defect-free and D allowing the largest visible knots and repairs. CDX, the most common structural grade, pairs a C-grade face with a D-grade back and exterior-rated glue.

What is the difference between plywood and OSB?

Plywood is made of cross-grained veneer sheets glued together, while OSB (oriented strand board) presses wood strands with wax and resin. Plywood generally holds screws better and handles moisture more predictably; OSB usually costs less per square foot for the same structural span.

Is plywood stronger than solid wood?

For panel applications, yes — the cross-grain construction resists warping and splitting better than a solid board of the same thickness. Solid lumber still outperforms plywood for load-bearing framing members like joists and studs, where plywood isn’t the material used anyway.

Can plywood be used outdoors?

Only exterior-rated (X) or marine-grade plywood should be used outdoors, and even exterior glue isn’t the same as fully waterproof. For permanent outdoor exposure like a boat hull or dock, marine plywood’s void-free core and fully waterproof adhesive are worth the added cost over standard CDX.

What’s the difference between softwood and hardwood plywood?

Softwood plywood uses pine, fir, or spruce veneers and is chosen for strength-to-cost in framing and sheathing. Hardwood plywood uses oak, birch, or maple face veneers and is chosen for appearance in furniture and cabinetry, usually over a lower-cost core.

How thick does plywood come?

Standard 4×8 sheets are most commonly stocked in 1/4-inch, 1/2-inch, and 3/4-inch thicknesses, with thinner 1/8-inch and 3/8-inch panels available for cabinet backs and underlayment. Baltic birch and specialty panels sometimes come in metric thicknesses like 12mm or 18mm instead.

Conclusion

The grade stamp and the type — not the price tag alone — are what determine whether a sheet of plywood is right for the job. A-grade hardwood plywood earns its higher cost on a visible cabinet face; CDX earns its lower cost hidden inside a wall or under a subfloor. Match the grade to where the panel actually ends up, and the sheet will outperform a guess made on price alone.