CDX vs. ACX Plywood: Which Grade Do You Need?
Walk into any lumberyard in Miami-Dade or Broward County and you’ll hear contractors ask for CDX or ACX without a second thought. But ask them to explain the difference and things get fuzzy fast. After more than 40 years supplying plywood to South Florida builders, roofers, and cabinet shops, we’ve answered this question thousands of times. Let’s settle it once and for all — so you order the right panel the first time and don’t waste money on a grade that’s overkill, or worse, end up with something that won’t hold up in our climate.
What Is CDX Plywood?
CDX is the construction workhorse of the plywood world. The letter “C” refers to the grade of the face veneer, “D” refers to the grade of the back veneer, and “X” denotes that the panel is bonded with an exterior-grade adhesive. That’s it — three characters that tell you almost everything about how the panel is built.
A C-grade face is unsanded and will show knots, patches, and minor splits — nothing pretty, but perfectly functional. The D-grade back is rougher still, and you may find voids where knots have dropped out. Because the back veneer falls below a C grade, CDX is technically classified as an Exposure 1 panel, not a full Exterior-rated panel. That distinction matters: Exposure 1 means the panel can handle temporary moisture exposure during construction, but it is not intended for permanent weather exposure without protection.
In South Florida, CDX is the go-to panel for roof sheathing, wall sheathing, and subflooring. It goes up fast, it’s strong enough for load-bearing applications, and it’s priced right for large-scale production builds where you’re nailing down hundreds of sheets in a day.
What Is ACX Plywood?
ACX steps up in quality on the face side. The “A” face is sanded smooth, with tight grain, minimal knots, and no open voids — the kind of surface that takes paint or a clear finish beautifully. The “C” back is still unsanded and serviceable, and the “X” bonding adhesive is the same exterior-grade glue used in CDX.
Because both the face and back veneers are C-grade or better, ACX earns a true Exterior panel rating. This means the bond is engineered to survive repeated wetting and drying cycles — a meaningful upgrade over Exposure 1 for applications where the panel may see ongoing moisture contact.
Cabinet shops love ACX for painted interiors and utility shelving where one side will be visible. Builders use it for soffits, exterior wall sheathing where the surface will be exposed before cladding, and anywhere a clean face matters. It costs more than CDX, but the price premium buys you a finished-looking surface and a stronger moisture-resistance rating.
Key Differences: CDX vs. ACX Side by Side
Here’s a quick breakdown of how these two grades stack up across the factors that matter most on a job site:
| Feature | CDX | ACX |
|---|---|---|
| Face Veneer Grade | C (unsanded, knots allowed) | A (sanded smooth, tight grain) |
| Back Veneer Grade | D (rough, voids possible) | C (unsanded but no open voids) |
| Adhesive / Glue | Exterior-grade (X) | Exterior-grade (X) |
| APA Exposure Rating | Exposure 1 | Exterior |
| Surface Finish | Rough, not suitable for paint | Smooth, paint- and finish-ready |
| Structural Use | Yes — sheathing, decking, subfloor | Yes — sheathing, soffits, cabinetry |
| Typical Cost | Lower | Higher (10–20% premium typical) |
| Best Application | Hidden structural framing | Visible or semi-exposed surfaces |
When to Use CDX — And When to Use ACX
The short answer: use CDX when the panel will be covered up, and use ACX when at least one face will be seen or needs a quality surface for finishing.
Reach for CDX when you’re:
- Decking a roof before felt paper and shingles go down
- Sheathing exterior walls before house wrap, stucco, or siding
- Installing a subfloor that will be covered by tile, hardwood, or carpet
- Building concrete formwork that will be stripped after the pour
- Working on a budget-sensitive production build where square footage is in the thousands
Reach for ACX when you’re:
- Building or lining utility cabinets, storage rooms, or shop shelving
- Installing soffits where the underside will be visible from the ground
- Sheathing an exterior wall where the surface will remain exposed temporarily and paint will be applied directly
- Doing any work where a clean, stable surface is required for laminating or finishing
- Constructing outdoor signage or covered exterior enclosures
Neither grade is a substitute for marine-grade plywood in applications involving constant water contact — boat hulls, docks, or submerged structures. For those jobs, you need a panel specifically engineered for continuous immersion.
South Florida–Specific Considerations: Humidity, Hurricanes, and Salt Air
Plywood grades that perform just fine in Atlanta or Charlotte can fail fast in Miami-Dade and Broward County. Our subtropical climate — with year-round humidity, intense UV exposure, hurricane-season rain events, and salt-laden coastal air — puts panels under stress that most of the country never sees. Here’s what that means for grade selection:
Humidity and moisture cycling: Even sheathing that never sees direct rain will absorb and release moisture as temperatures swing between air-conditioned interiors and the South Florida heat outside. Panels bonded with exterior-grade glue — both CDX and ACX — handle this better than interior-grade plywood, but neither is impervious. Proper sealing, drainage, and ventilation remain essential.
Hurricane building code: South Florida falls under some of the most stringent wind-load requirements in the country, governed by the Florida Building Code and the High-Velocity Hurricane Zone (HVHZ) provisions covering Miami-Dade and Broward counties. Roof sheathing thickness, nail pattern, and panel rating are all regulated. CDX sheathing at the correct thickness (typically 19/32″ or 5/8″ for most residential roof decks) is the standard specification for HVHZ compliance — consult your local building department and engineer of record to confirm what your specific project requires.
Coastal and marine environments: Within a few miles of the coast, salt air accelerates corrosion and degradation. If you’re building in a coastal zone — think Brickell, Miami Beach, Fort Lauderdale waterfront, or anywhere close to Biscayne Bay — give serious thought to upgrading hidden structural panels to a higher Exterior-rated product, and always use stainless or hot-dipped galvanized fasteners. ACX’s full Exterior rating gives it a slight edge over CDX in these environments for semi-exposed applications.
Cost Difference: Is ACX Worth the Premium?
In most South Florida markets, ACX runs roughly 10 to 20 percent more per sheet than comparable CDX. On a small cabinet shop project or a single soffit repair, that premium is trivial and absolutely worth paying for the surface quality. On a 10,000-square-foot roof deck with hundreds of sheets, that difference adds up fast — and for sheathing that will be completely covered, paying the ACX premium buys you nothing structurally.
The rule of thumb is straightforward: never pay for a finished face you’re going to bury. Use the grade the application demands, not the grade that sounds better. If you’re unsure what a specific job calls for, talk to a knowledgeable supplier who knows local code requirements — not just a box-store employee reading off a label.
Get the Right Panel for Your Next Project
Choosing between CDX and ACX plywood comes down to three questions: Will the surface be visible? Will the panel face ongoing moisture exposure? And what does the local building code require? Answer those honestly, and the grade choice is usually obvious.
At International Plywood & Lumber, we’ve been helping South Florida contractors, roofers, cabinet shops, and builders source the right plywood grades for over 40 years. Whether you need structural CDX sheathing for a hurricane-code roof deck or smooth ACX panels for a cabinetry project, we stock what the South Florida market demands — in the thicknesses, species, and quantities that keep your jobs moving. Visit us at discountplywood.com to check availability, get pricing, or connect with our team about your next order.
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