Plywood is a tried and true product. It is made up of thin sheets of pressed timber, glued together to form a solid sheet. MDF is is a relative newcomer that is being used more widely. It is created from wood particles combined with a chemical adhesive binder to create a solid sheet. Both products are used in a variety of furniture and cabinet-making applications and have many similar properties.
Both materials are typically sold in 1.2 x 2.4 m (4 x 8 foot) sheets in varying thicknesses. MDF is typically measured in millimetres and begins at 3 mm (1/8 inch) thick. Most plywoods begin at 6 mm (1/4 inch) thick. MDF and plywood are available with hardwood veneers for cabinet and furniture projects. While size and thickness are relatively identical, MDF is more than twice as heavy, but less flexible than plywood, giving it more potential to break when subjected to heavy loads without proper support.
Cutting and milling
Standard wood cutting tools, such as power saws, routers, and shapers, can be used on both materials. Plywood is typically coupled with hardwoods for decorative edges, due to the voids that can exist between layers, and the striped appearance of the layered edges. MDF can be shaped with virtually any wood working tool and is consistent in density and texture through the entire thickness. MDF will wear blades down slightly faster and may chip or burn when cut with dull blades.
Nails, screws, wood glue and other standard joining techniques are appropriate for either material. MDF is slightly more brittle and requires additional support for joints to keep it from splitting. Biscuit joiners, dowel rods and pocket screws work better in the consistent density of MDF, and both products work better if pre-drilled with pilot holes before using screws.
Plywood typically takes more filling and sanding to prepare a surface, except in the higher end products that are built with a hardwood veneer face. MDF has a tendency to absorb finishes more readily and is usually painted unless it has a veneer outer coating. Either product works equally well with solvent or water-based finish products and both should be well sealed if exposure to moisture will be a factor.
Finished product life
MDF or plywood can be used to construct quality, long lasting projects. MDF, due to its additional weight and more brittle texture, has a tendency to joint failure. While MDF is less susceptible to moisture than other manufactured wood products, plywood is preferable for pieces that will be exposed to rain and direct sunlight, as MDF will break down under extreme conditions. Finishes on MDF last slightly longer and minor changes in heat and humidity do not effect it as readily.