What is CDX Plywood?

CDX plywood is the workhorse of the construction industry. The name breaks down into three parts: C is the front face grade (allows tight knots up to 1-1/2 inch, knotholes up to 1 inch, and some repairs), D is the back face grade (allows larger knots, knotholes up to 2-1/2 inch, and limited splits), and X stands for exterior-rated adhesive (waterproof glue that holds up to moisture exposure during construction).

The "X" does not mean CDX plywood is an exterior-finish material. The glue is waterproof, but the face veneers are rough and unfinished. CDX handles temporary exposure during construction (roof sheathing before shingles go on, subfloor before the house is enclosed) but should not be permanently exposed to weather.

Standard sizes: 4x8 feet in 3/8, 1/2, 5/8, 19/32, and 3/4 inch thicknesses. The 1/2 inch and 3/4 inch panels are the most common for sheathing and subfloor applications. Pricing runs $25-45 per 4x8 sheet, making CDX one of the most affordable plywood options.

Common uses: roof decking, wall sheathing, subfloor underlayment, concrete formwork, and temporary construction surfaces. For concrete forms, CDX is preferred over OSB because its smoother face leaves a cleaner finish on the cured concrete.

Plywood face grades for reference: A is the smoothest (sanded, paintable), B allows minor repairs, C allows knots and repairs, and D allows the most defects. Cabinet-grade plywood uses A or B faces. Construction plywood uses C and D faces.

CDX vs OSB: both serve as structural sheathing with equivalent building code ratings. CDX costs more ($25-45 vs $15-30 for OSB) but handles moisture better. SmartCutList optimizes CDX sheet layouts and provides a smoother nailing surface. In regions with high humidity or prolonged rain during construction, CDX is often preferred.