CDX Grade
CDX is a plywood grade designation meaning C-grade face veneer, D-grade back veneer, and Exposure 1 (X) adhesive — the most common structural plywood grade used in residential construction for roof sheathing, wall sheathing, and subflooring.
In Detail
CDX Grade Explained
CDX is the industry shorthand for the most common structural plywood panel used in residential construction. The letters and number indicate:
- C = face veneer grade (knotholes up to 1-1/2" permitted, limited splits, synthetic repairs allowed)
- D = back veneer grade (knotholes up to 2-1/2" permitted, more defects allowed; not suitable for exterior exposure)
- X = Exposure 1 adhesive (waterproof phenolic resin glue bond — will not fail from moisture)
Important Clarification
The "X" in CDX does NOT mean "Exterior" grade — it means the adhesive bond is rated for Exposure 1 conditions (construction moisture exposure). The D-grade back veneer does not meet exterior exposure requirements, so CDX should not be used as permanent exterior cladding. However, the waterproof glue bond means the panel will not delaminate from construction-phase rain exposure.
Related Terms
Veneer Grade
Veneer grade is the quality classification of individual wood plies in plywood, ranging from A (smooth, paintable, minimal defects) to D (interior use only, knotholes up to 2-1/2" permitted), as defined by PS 1-09.
Exposure 1
Exposure 1 is a plywood adhesive classification indicating the panel uses waterproof glue that will not fail from moisture, but the panel is designed for temporary construction moisture exposure — not permanent outdoor use.