MDO and HDO plywood – a strong choice

MDO and HDO plywood are two of the most innovative lumber products to reach the market in many years, and are typically used as forms in the construction of concrete buildings such as high rises or sports arenas. What these two plywood products offer is the strength and light weight of veneer cored plywood combined with the consistent and smooth surface of engineered wood like MDF. As you can imagine, this smooth surface is extremely valuable when pouring concrete, because it leaves a smooth concrete surface that can then be painted or even left as an unfinished wall.

Types of plywood

There are several different types of plywood other than HDO and MDO. One of the least expensive products is MDF (Medium Density Fiber Core Hardwood Plywood), which is made of wood dust that has been mixed together with a binding glue and then formed into sheets. While this material has a clean surface that is perfect for adhering laminate to, it is not strong enough to withstand rough treatment. It is also a heavy material, which makes it somewhat difficult to use in overhead applications.

At the other end of the plywood spectrum is veneer core plywood, which is made of overlapping layers of thin veneer. While this overlapping makes veneer core plywood incredibly strong (this type of plywood is, proportionate to weight, as strong as steel), inconsistencies in the surface veneer can lead to flaws that will be visible after finishing. In addition, the overlapping grains of the many layers make it difficult to achieve a clean cut.

MDO Plywood

MDO plywood is a form of overlaid plywood. What this means is that MDO plywood starts with a core of overlapping veneer, much like traditional veneer core plywood. But instead of having a surface veneer of finished woodgrain, MDO plywood features a surface layer of medium density fiber, much like MDF. The result is a sheet of plywood that can typically be used once for forming concrete.

HDO plywood

HDO plywood is much like MDO plywood, except that the density of the fiber surface layer is much greater. This greater strength means that HDO plywood can usually be reused several times for forming. Thus the density of the surface layer is the distinguishing factor between MDO and HDO plywood.