Is marine plywood pressure treated?
No. Marine plywood is not pressure treated by default. Marine plywood relies on WBP phenolic adhesive (EN 314 Class 3 or BS 1088) and void-free hardwood veneers to resist water; pressure treated plywood relies on chemicals (ACQ, MCA, copper azole) injected into the wood to resist rot and insects. They are different processes. A small number of specialty products combine both, but the standard marine plywood at the lumberyard has not been chemically treated.
Is marine plywood better than pressure treated plywood?
Neither one is better in the abstract. They solve different problems. Marine plywood is the right call above the waterline, for structural work where panel voids would cause failure, and where face appearance matters for paint or stain. Pressure treated is the right call for ground contact, soil exposure, termite or fungus risk, and hidden subfloor or sheathing applications. Pick by water contact pattern and biological-attack risk, not by which one sounds more premium.
What are the disadvantages of marine plywood?
Marine plywood costs two to three times more per sheet than commodity plywood, and the price premium only pays back if cut edges are sealed at install. Unsealed edges allow water to wick into the inner plies, the WBP glue eventually hydrolyzes, and the panel delaminates from the inside. Marine plywood also carries no inherent insect or rot resistance, so for ground-contact or termite-prone installs it is the wrong product. It is water-resistant, not waterproof.
How long will marine plywood last outside?
Service life depends almost entirely on edge sealing and finish discipline. Properly sealed marine plywood with epoxy or polyurethane primer on every cut edge, plus a top-coat finish that gets refreshed every few years, can last 15 to 25 years above the waterline. The same panel installed without edge sealing typically delaminates within 3 to 5 years. The wood is engineered for longevity; the install determines whether the engineering matters.
Can pressure treated plywood replace marine plywood for boat work?
Not safely. Pressure treated plywood is built on commodity CDX core, which permits internal voids that can fail under structural load. The chemistry resists rot and insects but does nothing for delamination resistance once water reaches the glue lines. For transom skins, deck cores, hull repairs, and structural marine work, marine plywood with its void-free core and phenolic adhesive is the right product. Treated lumber is for ground contact, not over water.
Can you burn pressure treated plywood scrap?
No. Burning pressure treated plywood releases the preservative chemistry (copper azole, ACQ, MCA) into the smoke, which most jurisdictions regulate as hazardous waste. PT scrap goes to landfill or to a permitted construction-debris facility. Marine plywood scrap, by contrast, is just wood and exterior phenolic glue, and can be burned safely or sent to standard wood-waste recycling.
