What CDX plywood is
CDX is a trade name for a softwood plywood grade used mostly in construction. It is common for roof and wall sheathing and for subfloors, where the surface is covered later. It is not usually chosen for visible furniture or cabinet faces, because the veneers can have knots, patches and rough areas.
CDX is a grade, not a family with several sub-types. When people ask about “types of plywood CDX”, they usually want to know what the letters mean and how CDX compares with other grades.
What the letters mean
- C: the face veneer. It is sound but allows knots, repaired spots and colour variation.
- D: the back veneer. It is rougher than the face and can have larger knots and open defects, because it is meant to be hidden.
- X: refers to the type of glue, generally described as an exterior-type or Exposure 1 adhesive.
Exposure 1 is typically described as meant to withstand moisture from construction delays, such as rain before the roof is on. That is not the same as being approved for permanent outdoor weather exposure. Check the stamp on the actual panel and the manufacturer’s literature.
Other common grades
| Grade | Face | Back | Typical use |
|---|---|---|---|
| AC | A | C | Visible face with a hidden back |
| BC | B | C | Utility surfaces, painted work |
| ACX / BCX | A or B | C | As above, with exterior-type glue |
| CDX | C | D | Hidden structure, sheathing |
In this system, A is the smoothest with the fewest defects, and D is the roughest. Grade letters mostly describe appearance of the veneer. Whether a panel suits damp conditions depends on the bond or exposure classification stamped on it. Other grading systems exist for hardwood plywood and for panels made outside North America, so letters are not interchangeable between them. For a wider look at the options, see furniture plywood types explained.
CDX vs ACX and BC plywood
Readers often ask whether ACX or CDX is better. It depends on the job. ACX has a smoother A face, so it is a better fit where one side will be seen or painted, such as some outdoor-style projects once sealed. CDX is typically chosen for hidden structural layers where appearance does not matter.
BC plywood has a B face and a C back, with no exterior-type glue assumed from the letters alone. Compared with CDX, the face is smoother. The glue still needs confirming on the panel stamp, as the letters do not guarantee it.
CDX vs OSB
Both CDX plywood and oriented strand board are used for roof, wall and floor sheathing. Plywood is made from layered veneers, OSB from compressed strands. Opinions vary on which is better. Plywood is often described as handling edge moisture and fastener holding well, while OSB is often described as more uniform. Performance depends on the rating, thickness and installation, and building codes may specify which panel ratings are acceptable, so follow the local code and the panel’s span rating rather than a general rule. For furniture and cabinet work, neither is a typical first choice.
Where CDX is used, and where it is not
Commonly used for:
- Roof and wall sheathing
- Subfloors beneath finish flooring
- Temporary protection and work surfaces
- Workshop shelving, jigs and utility builds where looks are not important
Usually avoided for:
- Cabinet boxes, drawers and visible furniture
- Surfaces that need a smooth finish without heavy filling and sanding
- Permanent outdoor exposure without protection
Is CDX waterproof?
No. CDX is not waterproof. The glue is intended to tolerate temporary wetting during construction, but the wood can still absorb water, swell at edges and eventually degrade if it stays wet. Sealing edges, covering the panel promptly and keeping it off wet ground all help; our guide to waterproofing wood covers sealing in more detail. For related questions, see is hardwood plywood waterproof and is laminated plywood waterproof.
Working with CDX safely
- Wear gloves, eye protection and a dust mask. Rough veneers can splinter and cutting raises fine dust.
- Support sheets fully when cutting and keep hands clear of the blade path. Use a guide for circular saw cuts and follow the tool manual.
- Pre-drill near edges when needed to limit splitting, and use fasteners suited to the application.
- Store panels flat and dry. If you paint or seal them, use the product in a ventilated area away from flames and sparks, and dispose of solvent-soaked rags as the label directs.
- Panels can be heavy and awkward. Get help carrying full sheets.
FAQ
What are the four types of plywood? There is no single official list. Commonly the groups are softwood, hardwood, marine or exterior, and decorative or specialty panels.
What is the difference between CDX and BC plywood? The face is smoother on BC (B vs C), and the glue should be confirmed from the stamp.
Is CDX good for cabinets? Generally no, because of the rough faces and possible voids. See plywood grades for cabinets for what to buy instead.
Is CDX exterior grade? It uses exterior-type glue, but that does not make it suitable for unprotected permanent outdoor use.