Can I use CDX plywood for exterior siding?

No, CDX is for sheathing; use siding-rated T1-11 or similar exterior-rated panels.

What is the difference between CDX and OSB?

CDX is made of wood veneers while OSB is made of compressed strands; CDX holds nails better in high-stress applications.

Does the 'X' mean it is waterproof?

The 'X' indicates Exposure 1 glue, which is moisture-resistant but not intended for permanent weather exposure.

Why do my panels have gaps?

Small voids in the D-grade back veneer are standard and do not affect the structural integrity of the panel.

CDX Plywood Sheathing

Plywood & Sheathing

Sheathing

$35.00 to $65.00 per 4x8 sheet based on current 2026 market averages for 1/2 inch to 3/4 inch thickness.

CDX Plywood Sheathing Overview (2026)

Prepared by Lumberama's Building Materials Team

|Last updated September 3, 2026|Sources & methodology

CDX is a construction-grade plywood manufactured with C-grade veneer on the face, D-grade veneer on the back, and exterior-grade glue (X). It is intended for structural applications in subflooring, wall sheathing, and roof decking. It is not an appearance-grade panel and typically features core voids and surface patches.

Key Features

APA-rated structural performance. - Exterior glue line allows for moisture exposure during construction. - Available in common span ratings including 24/16
32/16
and 48/24. - Tongue and groove (T&G) options available for subfloor applications.

Specifications

Common thicknesses: 3/8 inch (10mm)

1/2 inch (12mm)

5/8 inch (16mm)

3/4 inch (19mm). - Standard panel size: 4 feet by 8 feet. - Grade: C-D Exposure 1. - Moisture resistance: Rated for temporary exposure to moisture but not for permanent exterior use.

Applications

Roof decking for asphalt shingles or metal roofing. - Wall sheathing for siding support. - Subflooring for tile
hardwood
or carpet underlayment. - Structural bracing in light-frame construction.

Installation Overview

- Install with grain running perpendicular to supports. - Leave 1/8 inch gap at panel edges for expansion. - Fasten at 6 inches on-center at edges and 12 inches on-center in the field using 8d common nails for panels up to 1/2 inch thick.

Pros & Cons

Pros

✓ High strength-to-weight ratio. - Superior screw-holding capability compared to OSB. - Moisture-resistant adhesive resists delamination during rain delays.

Cons

✗ Subject to surface checking and swelling if left exposed for extended periods. - Inconsistent face appearance. - Higher cost compared to OSB structural sheathing.

Code Requirements

- Must comply with PS 1-09 structural plywood standards. - Requires APA-EWS stamp on every panel. - Must be installed per International Residential Code (IRC) shear wall and diaphragm specifications.

Buying Tips

- Check for the APA stamp on the back or face of the panel. - Inspect for severe bowing or delamination of edges before purchase. - Select T&G panels for flooring to ensure edge support between joists.