MDF, or medium-density fiberboard, is a building material composed of wood fibers, resin, and other additives. These components are processed together under high heat and pressure to form a dense and uniform panel.
MDF offers several advantages over real wood including dimensional stability, ease of workability, and cost. While there are also disadvantages to using MDF, its smooth surface and uniform composition make it an excellent choice for interior trim, cabinetry, and furniture.
Due to its versatility and affordability, MDF is a favorite material for both building professionals and DIY enthusiasts alike.
What is MDF?
MDF is an engineered, composite building product formed by bonding wood fibers, which are cellulose strands extracted from wood, similar to fibers used to create paper. Manufacturers bind these fibers together with a resin binder, water, and paraffin wax. MDF boards have a density range between 500 to 1,000 kg/m3 with an average density between 600-800 kg/m3.
Manufacturers create MDF in a process called “dry forming”. During this process, the wood fibers are mixed with resin and compressed using high pressure and heat. The resulting panel has a uniform density throughout, giving it consistent dimensional stability and strength.
Because it is a manufactured product, MDF does not have knots, wood grain, or voids. This makes it ideal for applications that require a smooth, uniform, and unblemished surface. MDF is available in different thicknesses and sheet sizes to suit a wide variety of applications.
Types of MDF
MDF is popular in many building applications, so manufacturers have created diverse types of MDF to suit this wide range of building applications. These types differ in their exact composition, additives, and properties.
Standard MDF is the most common type and is suitable for a wide range of interior projects. It has a consistent density and smooth finish and is easy to shape and cut.
Moisture Resistant (MR) MDF is created to have greater resistance to moisture and humidity with the use of water-resistant additives. This type of MDF is optimal for bathrooms and kitchens and other moisture-prone environments. Most MR MDF is green in color because the manufacturers add green dye to the mixture to set these boards apart from standard MDF.
Fire-retardant MDF is created by mixing fire-retardant additives into the wood fibers during the manufacturing process. Builders use these boards for commercial applications where fire codes are more strict. Fire-retardant MDF boards are red to differentiate them from other types of MDF.
Exterior Grade MDF
Standard MDF is not resistant enough to withstand outdoor conditions. Exterior grade MDF has enhanced resistance to weathering, humidity, and UV damage. This type of MDF is common in outdoor trim and signage.
Manufacturers create ultralight MDF using lightweight materials or modify the density of the product during the manufacturing process. This MDF has similar properties to standard MDF, but it is lighter in weight, so it is easier to handle and transport. Ultralight MDF is not as strong as standard MDF.
Veneered MDF has a similar structural composition as other MDF boards, but it has a thin sheet of wood veneer bonded to the surface. This product creates the look of solid wood, but it still has the uniformity and strength of MDF.
Manufacturers create bendy MDF, also called flexible or bendable MDF, to be more flexible than standard MDF. They create this flexibility by heating the wood fibers to soften them. This allows builders to bend or curve the MDF into desired forms. The bending radius depends on the thickness of the panel.
Standard MDF Sizes
- Thickness – MDF panels are available in a range of thicknesses from ⅛ inch (2.5 mm) to 1 inch (25 mm). The thicknesses available can vary according to the manufacturer and region.
- Width – The most common standard MDF width is 4 feet, but there are other length boards available including 5 feet and 8 feet.
- Length – The most common standard length for MDF boards is 8 feet, but you can find boards that are as long as 25 feet.
Pros and Cons of MDF Compared to Real Wood
Some people view MDF as inferior to wood, and though it is different, it has some distinct advantages over wood for certain projects and under certain conditions.
- Affordability – MDF is generally less expensive than most types of softwood and hardwood. This makes it suitable for people on a limited budget.
- Uniformity – MDF has a consistent density and a uniform composition. This means that it is less likely than wood to have holes, knots, irregular wood grain, voids, and other imperfections.
- Smooth Surface – The smooth surface of MDF is ideal for painting, veneering, or applying laminates to result in a flawless finish.
- Stability – MDF is less prone to twisting, warping, and shrinking, compared to real wood. This makes it ideal for applications that require dimensional stability.
- Versatility – It is easy to shape, cut, and route MDF boards, so it is useful for creating detailed molding, furniture, and cabinetry.
- Durability – MDf is not as durable as real wood and is more prone to scratches, dents, nicks, and moisture damage.
- Weight – MDF is heavier than natural wood, so it is more challenging to handle and transport.
- Limited Strength – MDF is a strong material, but it is not as strong as real wood. This makes it less suitable for load-bearing or heavy-use applications.
- Environmental Impact – Manufacturers create MDF using recycled or waste-wood fibers, so this is beneficial to the environment. But the process to create MDF uses resins and adhesives that contain formaldehyde, a carcinogen, or other volatile organic compounds (VOC) that will continue to off-gas until you seal the board with paint.
- Limited Repair Options – You can repair real wood elements that sustain damage by sanding and repainting or staining. It is difficult to seamlessly repair MDF due to its composite nature.