Pressure-Treated Plywood and Concrete Form Plywood

Pressure-treated plywood protects wood against decay and insects; concrete form plywood holds fresh concrete while it hardens. Buy treated plywood for a floor or sheathing job where damp conditions make decay protection worth having, and form plywood for the pour. Getting that choice right matters because preservative treatment, exterior glue and a concrete-forming surface do different jobs.

Pressure-treated plywood: 3/4-inch and 1/2-inch 4x8 sheets

For a moisture-prone subfloor, buy the 3/4-inch 4x8 treated plywood. The thicker panel provides added sturdiness, and pressure treatment puts preservatives into the wood while maintaining its strength and workability. That’s a useful combination under a floor you expect to keep.

The 1/2-inch 4x8 treated plywood is the pick for sheathing work that calls for a 1/2-inch panel and decay protection. Treated plywood serves both wall and roof sheathing jobs. Set the structural rating and thickness for the building or form design first, then match the treatment to the exposure. Treatment protects the wood; it does not replace the thickness needed to carry the load.

If you’re comparing 5/8-inch pressure-treated plywood with 3/4-inch, both thicknesses provide added sturdiness for damp subfloors and exterior sheathing. Among these WBC treated panels, the 3/4-inch sheet is the buy for that work.

Panel	Thickness	Sheet size	Buying decision
Pressure-treated plywood	3/4 inch	4 feet by 8 feet	Buy for added sturdiness in damp subfloors and exterior sheathing.
Pressure-treated plywood	1/2 inch	4 feet by 8 feet	Buy for 1/2-inch sheathing work needing decay protection.
Concrete form plywood	3/4 inch	4 feet by 8 feet	Buy for concrete forms.

Is CDX plywood pressure-treated?

CDX alone does not mean pressure-treated. Plywood gets its preservative protection through a separate pressure process. Identify pressure-treated plywood by an explicit pressure-treatment designation, separate from the panel’s grade or glue-bond designation.

Standard BCX plywood is not pressure-treated. Its exterior-rated adhesive describes the glue, not preservative protection in the wood. For ground-contact or permanently wet work, buy plywood with treatment suited to that exposure instead of substituting standard BCX.

Outdoor use, ground contact and waterproofing

Pressure-treated plywood is the right category for outdoor work where decay protection matters. In Montana, spring snowmelt keeps ground wet for weeks. A panel beside that wet ground faces a different job from sheathing that gets enclosed during the fall push before freeze.

For ground-contact work, match the treatment’s use category and preservative retention to the actual exposure. Thickness and the word “treated” are separate buying decisions from ground-contact suitability.

Treated plywood is not made waterproof by pressure treatment. You’re buying protection against decay and insects, so drainage and keeping water out of the assembly still matter. For boat work, choose plywood and treatment suited to the boat’s construction and its freshwater or saltwater exposure; ordinary exterior use is a different service condition.

Subfloors and painted work

Yes, you can use pressure-treated plywood for subflooring in potentially damp conditions. The 3/4-inch 4x8 sheet is the strong pick here because its added sturdiness suits that job. Correct the source of persistent water during a repair so the new floor gets both preservative protection and a drier assembly.

You can paint pressure-treated plywood with a paint-compatible treatment. Choose the preservative and finish together: oil-free treatments suitable for painting serve a different finishing job from oily treatments such as creosote or oil-borne penta.

Concrete form plywood: 3/4-inch 4x8 sheets

Buy WBC’s 3/4-inch 4x8 concrete form plywood when you’re building the mold for a concrete pour. Form plywood supports fresh concrete until it sets and hardens. That’s the job to buy it for on foundation, slab and wall work.

Keep forming use separate from preservative treatment. Pressure-treated plywood can also serve in concrete forming, but choose a panel for both requirements when the job needs both. Calling a panel “form plywood” identifies its forming purpose, not a pressure-treatment process.

The form’s supports and concrete load belong in the selection alongside panel thickness. A 3/4-inch sheet is one part of the form, not the whole support system. In Montana’s short building season, settle that choice before the pour gets squeezed against fall freeze.

The Pick

Buy the 3/4-inch 4x8 pressure-treated plywood for damp subfloors and exterior sheathing needing added sturdiness. Buy the 1/2-inch 4x8 treated plywood for 1/2-inch sheathing work needing decay protection. For concrete forms, buy the 3/4-inch 4x8 concrete form plywood.

Frequently Asked Questions

Is treated plywood waterproof?

Pressure-treated plywood resists decay and insect attack, but treatment doesn’t make it waterproof. You still need drainage and a way to keep water out of the assembly. Preservative protection won’t fix a detail that traps water against the wood.

Is CDX plywood pressure-treated?

CDX plywood isn’t automatically pressure-treated, and standard BCX isn’t pressure-treated either. An exterior-rated adhesive describes the glue bond, not decay protection in the wood. If your job needs preservative protection, choose a panel explicitly identified as pressure-treated.

Can you use pressure-treated plywood for a subfloor?

Yes, pressure-treated plywood is used for subfloors in potentially damp conditions. A 3/4-inch panel provides added sturdiness, though the floor’s loads and supports still govern panel selection. If you’re replacing a water-damaged floor, correcting the moisture problem matters just as much as adding decay protection.

Can you paint pressure-treated plywood?

Yes, you can paint pressure-treated plywood when its preservative treatment is compatible with paint. Let the wood dry thoroughly before finishing; a surface that feels dry isn’t proof that the whole panel has dried. Drying matters, but it won’t turn a treatment that’s unsuitable for painting into a paintable one.