U. S. Lumber, Inc. HDO

MDO and HDO Plywood



Medium Density Overlay (MDO) and High Density Overlay (HDO) Plywood (also called signboard) are engineered wood panels, originally designed for sign makers. However, they are gaining popularity for other purposes. Cabinetmakers are beginning to see the value of these engineered woods and use them. They are also excellent products for jigs and cement forms.



Both MDO and HDO are hardwood plywoods with a resin soaked fiber overlays between the veneer layers and on both surfaces. The top veneer layer on both sides is “A” grade, providing for an extremely smooth surface, without voids, to apply the fiber overlay. The resin-soaked fiber overlays are applied with heat and pressure, forming an extremely strong, extremely flat and extremely smooth engineered wood product that is waterproof. The only differences between the two products are that the density of the exterior fiber layer on the HDO is considerably higher than for MDO and it is manufactured with higher resin content.


MDO and HDO are both available in a variety of thickness, including 3/8”, 1/2”, 5/8”, 3/4” and 1”. Standard sheet sizes include both 2 and 4 foot widths, and lengths of 8’, 10’ and 12’.



When used for cabinetmaking, MDO panels provide an excellent, very flat surface that accepts paint very well. The resin impregnated fiber layer adheres well to paint and eliminates the need for priming. Unlike many other materials, cut edges are still highly water resistant, with the added benefit of being easily painted, fully sealing the edges against water.


Application and cost

HDO plywood was originally created for use in making highway signs where reflective material is attached to the surface of the sign. To make a more durable sign, it was decided that a more robust resin layer was needed in order to provide a better surface for attaching the reflective material. These materials are not as commonly available as softwood plywood. Consumer building supply centers normally will not carry them, but lumberyards that cater to professions probably will. MDO plywood costs about half the cost of marine plywood, or about twice the cost of softwood plywood; HDO is slightly higher.



The superior hardwood strength properties of Finnish White Birch combined with thin multiple veneer panel construction makes FinnForm the benchmark for quality in the plywood forming industry. The 220g/m2 phenolic surface film on both faces provides very high reusability while producing good, well-compacted concrete. That is why architects and specifiers select FinnForm for high profile concrete projects throughout the country. There is only one FinnForm—easily identified by its red colored film faces. FinnForm is available in thicknesses from 1/4" to 1 1/2". Standard sizes are 8'x4', 5'; 10'x4', 5'; 12'x4', 5'

A special FinnForm panel is available for re-plying metal framed forms. This is FinnForm Reply, manufactured in full 1/2" thickness, 4'x8' size (face grain runs the length direction). The durability of FinnForm plywood out performs HDO and lasts longer. So, when replacing (re-plying) your metal framed forms, FinnForm Reply is the way to upgrade your forms.

Euroform Plywood
Euroform is made with the same high quality construction as Eurobirch with the addition of thermally fused phenolic facings for durability and moisture resistance. It is excellent for pattern plates or core box construction. Euroform features:
• Solid Birch construction
• Virtually void free laminates
• Phenolic resin adhesive that is waterproof & boilproof
• Thin veneers for maximum strength & durability