What does HDO stand for in plywood?
HDO stands for High Density Overlay. It refers to a plywood panel with a high-density resin-impregnated fiber overlay bonded to one or both faces under heat and pressure. This overlay creates an extremely hard, smooth, and abrasion-resistant surface ideal for concrete formwork, signage, and industrial applications.
What is HDO plywood used for?
HDO plywood is used primarily for concrete formwork where a smooth, architectural-grade concrete finish is required. The hard overlay surface produces clean off-form concrete with minimal finishing needed. Other common uses include highway signs, industrial work surfaces, and marine applications where a durable, moisture-resistant panel is essential.
Is HDO plywood waterproof?
HDO plywood uses WBP (weather-and-boil-proof) phenolic adhesive throughout its core and a resin-saturated overlay on the face, making it highly water-resistant. No wood product is truly waterproof indefinitely, but HDO panels resist moisture penetration far better than standard plywood. Sealing cut edges and maintaining the overlay surface extends its performance in wet environments.
What is the difference between HDO and MDO plywood?
The key difference is overlay density and surface finish. HDO has a harder, denser overlay that produces a glossy, smooth surface ideal for exposed concrete. MDO has a lighter overlay that produces a matte, paintable surface suited for signage, siding, and moderate-finish formwork. HDO typically costs more but delivers more reuse cycles in formwork applications.
How much does HDO plywood cost?
As an approximate 2026 guide, HDO plyform runs about $70–95 for a 1/2" 4×8 sheet up to roughly $135–195 for 1-1/8", at US retail. Ranges move with overlay grade, core species, and the lumber market, and wholesale or factory-direct import is lower at container volume. For formwork the figure that matters is cost per pour: a panel rated for up to 50 reuses spreads its price across far more concrete. Verify a current quote before budgeting.
