Overlaid Panels (HDO and MDO)
Demanding applications such as concrete forming, exterior siding, and industrial containers require tough building materials. APA trademarked High and Medium Density Overlay plywood (HDO and MDO) combine the toughness of Exterior-type plywood with the superior wear of an overlaid surface. These features place HDO and MDO among the most durable construction materials on the market today.
HDO and MDO feature highly durable, resin-impregnated fiber faces. The thermoset resin, bonded under heat and pressure, forms a very tough surface that easily resists abrasion, moisture penetration, chemicals, and deterioration. HDO is manufactured with more resin than MDO, but both are far more durable than standard plywood and are ideal for use in the most punishing of applications. Yet they retain plywood’s advantages, such as high strength to weight ratio, dimensional stability, and rack resistance, as well as plywood’s design flexibility; panels are available in large sizes and can be worked with common woodworking tools.
HDO is available in two grades, Concrete Form and Industrial, and MDO is available in Concrete Form and General grades. Concrete forming grades are both ideal for reuse under the harsh conditions of concrete formwork; HDO leaves a smooth “steel-form” finish while MDO leaves a matte finish. Both may be reused for concrete forming many times, but HDO has a longer use life. Industrial grade HDO panels are commonly used for highway panels, industrial tanks, and other highly demanding applications. General grade MDO is manufactured to be an ideal paint base and is used for structural siding, soffits, and other exterior applications where long-lasting paint or coating performance is required.
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