LumberCalcs: The Straight-Grain Figures for the Hand-Hewn Builder
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CDX Plywood

For subfloors, roof sheathing, and wall sheathing -- unfinished structural plywood where appearance doesn\'t matter.

Runner-up: OSB · Retake the quiz

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Why this fits you

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  • You\'re sheathing a floor, wall, or roof that will be covered.
  • Appearance of the panel face doesn\'t matter -- it\'s structural, not visible.
  • You want a cost-effective structural panel.
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CDX plywood (C-grade face, D-grade back, Exterior glue) is the standard structural sheathing plywood for subfloors, roof decks, and wall sheathing -- built for strength and exterior-glue moisture resistance, not appearance. Both faces have visible knots, patches, and grain defects, which is fine since the panel gets covered by flooring, roofing, or siding.

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How it compares

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OptionBest forFinishCost
CDX PlywoodStructural sheathingUnfinished, C/D grade faces$
OSBBudget structural sheathingUnfinished, strand pattern$
ACX / Marine-Grade PlywoodOne visible face, moisture exposureA-grade face, C-grade back$$
Baltic Birch PlywoodFurniture, cabinetry, fine joinerySmooth both faces, visible edge plies$$$
MDFPainted trim, indoor cabinetryUltra-smooth, uniform, no grain$$
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Buying checklist

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  • Confirm thickness matches your span rating (check your joist/rafter spacing against the panel\'s rated span)
  • CDX is not meant to stay exposed to weather long-term despite the exterior glue -- cover it promptly
  • Not the right choice for anything where the panel face will be visible or painted
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Run the numbers

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Lumber Cost CalculatorPlywood Calculator
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Frequently asked questions

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What does CDX stand for?

C and D refer to the grade of each face (C being better than D), and X means exterior glue -- the panel is bonded with moisture-resistant adhesive, though the wood itself isn\'t weatherproof long-term.

Can I use CDX for a project where it\'ll be visible?

Not ideally -- CDX has knots, patches, and visible defects on both faces since it\'s built for structural use under a covering, not appearance.

Is CDX waterproof?

No -- the exterior glue resists moisture better than interior-glue panels, but the wood itself will still absorb water and degrade if left exposed to weather for extended periods.

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Other Plywood Type Finder results

OSB (Oriented Strand Board)ACX / Marine-Grade PlywoodBaltic Birch PlywoodMDF (Medium-Density Fiberboard)
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