Everything You Need to Know About MDF Doors

Post by manhattandoor on June 26th, 2023

MDF is an engineered wood product that is made by compressing hardwood or soft wood fibers with resin and wax under high temperatures and pressures. Denser than both plywood and particleboard, it is commonly used in both residential and commercial door construction. In this guide, we will cover the most important topics related to MDF doors, including their manufacturing process, their pros and cons and how they compare to solid core interior doors.

MDF Door Meaning

MDF stands for medium density fiberboard, an engineered wood product manufactured from recovered and recycled wood fiber. It was developed as a more affordable and durable alternative to natural wood, as it resists cracking, warping, expanding, shrinking and splitting. It also provides a smoother surface for painting than many types of wood, including pine and poplar.

How Is an MDF Interior Door Made?

In this section, we will delve into the manufacturing process, which will help explain how MDF gets its strength and durability. During this process, MDF panel doors are compressed to high densities ranging from 31 to 50 pounds per cubic foot in a hot press. The whole interfiber bond is made using an organic binder or synthetic resin.

MDF differs from particleboard in several notable ways:

• Density: MDF has a density that is more uniform.
• Machinable edges: MDF features tight, smooth edges that can be machined.
• No need for laminates: Furthermore, it can be finished to a smooth surface and grain printed, which eliminates the need for laminates and veneers.

Thicker MDF panels, which range from 1/2 inch to 3/4 inch, are often used as core materials in furniture panels. MDF panels with thicknesses less than 1/2 inches are commonly used in siding.

The MDF Manufacturing Process

The typical steps to manufacture MDF include the following:

1. Delivery or Preparation of Wood Chips

In most cases, the furnish for MDF is wood chips. This material is usually delivered by rail or truck from plywood plants, sawmills, satellite chip mills, whole tree chipping operations and other off-site places. In some facilities, wood chips are prepared at the site. In this case, logs will be debarked, cut down to lengths that are more manageable and sent to chippers. If needed, the chips may be washed to take out debris.

2. Refinement of Wood Chips

The wood chips are then put in a digester that is steam-pressurized, where they are softened. Then, they are put into a refiner chamber, where revolving disks pulp the softened chips into wood fiber material that can be used to manufacture the board.

3. Drying

Next, the fibers move to a drying area. Sometimes, the wood chips will be initially dried in a rotary predryer, but in any case, the chips will pass through tube dryers, which reduces the wood fibers’ moisture content to the levels needed. MDF door manufacturing commonly uses single-stage or multiple-stage tube drying systems. The tube dryers with multiple stages have a main tube dryer and a second-stage tube dryer separated by a cyclonic collector or another emission point. The heat in tube dryers is generally provided by natural gas, distillate oil, propane or by indirect heating.

4. Blending

The wood fibers then move into the blending area, although the order of the drying and blending operations will depend on which method is used to blend the fibers with resins and other types of additives.

The resins most commonly used when manufacturing MDF are urea-formaldehyde, although melamine resins, isocyanates and phenolic resins are used as well. Certain facilities will inject resin formulations in a short-retention blender, although the majority of plants inject resins into blowline systems.

If a resin is injected into a separate blender, the fibers are dried and separated from the stream of gas first using a fiber recovery cyclone, after which they travel into the blender. These wood fibers are subsequently mixed with wax, resin and other additives, after which they travel to a dry storage container.

5. Mat Forming

Air will then convey resinated fibers out of the storage bin and into the forming machine. Here, they are deposited onto a screen system that is continuously moving. This continuously formed mat needs to be pre-pressed before it is loaded on the hot press. After this pre-pressing step, the mat will undergo some pre-trimming. The material that is trimmed will be collected and sent back to the forming machine.

6. Hot Pressing

The mats that have been prepressed and trimmed will then travel to the hot press. This press will apply pressure and heat to make the resin active, which will bond all the wood fiber material into one, solid panel door. In some cases, the mat might be pressed in a continuous hot press, and in others, the pre-compressed mat might be cut into individual mats using a flying cutoff saw. These mats are subsequently loaded in a batch-type, multi-opening hot press. Hot oil or steam heating of the platens is common with domestic facilities.

7. Preparing the Finished Product

Once pressing has finished, the boards are cooled down, sanded and trimmed. Then, they are sawed down to their final dimensions. Painting and laminating may also occur during this step.

Finally, the finished MDF product will be packaged to be shipped, where it will be used to manufacture interior doors, cabinets, flooring, wainscotting and various other wood products.

Benefits of MDF Doors

MDF doors offer a number of benefits over their solid wood counterparts, including:

1. No Warping

Like wood, MDF will contract and expand as a result of humidity and temperature fluctuations. However, MDF is unlike wood in that it will not warp. This is thanks to the board’s structure, which allows it to move as a unit. Even when temperature and humidity changes are extreme, wood damage will not be a concern. No more worrying about your warped wood doors not fitting in the door frame!

Solid wood doors are extremely vulnerable to heat and cold, and rapid fluctuations in humidity and temperature can have a negative effect on solid wood doors. Even though advancements have been made in technology and manufacturing, wooden doors still experience some degree of contraction and expansion.

2. Smoother Finish

MDF board consists of particles that are extremely fine, which means there is no noticeable grain. The result is a better, smoother finish, especially if painted. If your customers want to paint their doors, recommend MDF doors over solid wood doors.

3. More Customizable

Because of the structure of MDF boards, they can be drilled and cut in a wide variety of ways without being damaged. This gives you a ton of design flexibility with your door. MDF door material makes them easy to customize and explains why so many door styles using MDF are available. MDF doors also come in larger sizes. For customers who need a big piece of wood without joints, MDF is often the best option.

4. Better Water Resistance

With solid wood doors, moisture is a common issue. While a wood door can be protected fairly well with a good finish, if the surface is accidentally scratched, this can make it vulnerable to moisture, which can attract mold. Mold is very adaptable, and just a small crack is needed for a colony to grow.

MDF doors can be designed to be moisture-resistant. Homeowners who plan on installing a door in their bathroom or other places with high moisture should be advised to get MDF boards specially designed to be exceptionally water-resistant, as normal MDF boards can still be easily damaged when exposed to water.

5. More Affordable

With MDF doors, homeowners can get the strength and longevity of a solid wood door at a lower price. Although not all solid wood types are pricey, the majority are. Many of the most popular wood species such as walnut, cherry and white oak are considerably expensive, and scarcer species like mahogany and teak can be extremely costly. The three factors that most affect pricing are aesthetics, durability and availability.

6. Easier to Supply

Another benefit of MDF is that it is easier to find something like white oak or maple, especially for customers looking for a specific size & style.

7. Fire Retardant

There are also MDF doors that are fire retardant. Although this type of MDF door is most commonly found in commercial buildings, it can also be used in homes for fire protection, especially for areas like bedrooms and kitchens.

8. Easy to Work With

As MDF is made from wood byproducts, contractors will have no trouble cutting, routing or drilling it with their regular woodworking tools. It is also possible to fasten MDF parts together using a wide variety of screws or nails. Even pocket screws work. MDF pieces can also be glued together with practically any adhesive type, including door construction adhesive, polyurethane glue and carpenter’s glue.

9. Environmentally Friendly

Purchasing MDF doors is an environmentally friendly decision. MDF comes from recovered and recycled wood waste, which would otherwise be thrown in a landfill or burned. MDF makes better use of natural wood resources and optimal use of every tree. In fact, MDF uses close to 100% of every tree that is used to make this product, as opposed to solid lumber, which only uses about two-thirds of every tree.

Some other reasons that MDF is environmentally friendly include:

• MDF has less of an environmental impact: Wood products do not require as much energy to manufacture as most other building products. They do not create as many environmentally harmful byproducts and can be recycled or reused. They also have a lower impact on the environment over the course of their life.
• MDF is biodegradable and renewable: MDF, like all wood products, is 100% biodegradable once its service life is over and comes from a natural source that is 100% renewable and sustainable. This is not true of concrete, plastic or metal.

How Much Does MDF Cost?

There are a number of options for contractors and their clients when it comes to the wood product they choose for their interior door. If a buyer has a budget, price will probably be a major factor. In this section, we will give you an idea of MDF door prices and how they compare to those of other wood products:

• MDF door: The price of an MDF door is generally several hundred dollars, although some are extremely cheap. MDF doors can be fully solid, hollow core or solid core, and many door styles are available. They offer more stability than their solid wood counterparts because they are less affected by humidity and provide an extremely smooth surface for painting. Although generally flat and smooth in appearance, MDF doors are also available in other styles. When completely solid, MDF doors are often quite heavy.
• Hollow core door: Hollow core doors are among the cheapest options available, with prices rarely exceeding several hundred dollars. A hollow core door consists of a skin or shell made from wood, vinyl or MDF with nothing inside. These doors weigh very little, can be installed quickly and are quite affordable. However, they are not known to block sound very effectively. Hollow core doors are popular options for closet doors but are also commonly used for passages and bathrooms. They come in a variety of door sizes and door styles.
• Composite door: Composite doors can also be reasonably priced, although they commonly cost considerably more than their MDF and hollow core counterparts. As the name suggests, a composite door can consist of a mixture of various materials, including wood, MDF and plastic. The cost of a composite door will vary from one door to another, so customers should check the price before they order. They generally require little maintenance, but be aware that some composite doors are negatively affected by moisture.
• Solid wood door: Solid wood doors are priced similarly to composite doors. They consist of one single wood piece and come in many door styles, ranging from plain to highly decorative. Popular wood species for solid wood doors include poplar, maple, ash, walnut and oak. Remember that the more durable and exotic the wood species, the more it will cost.
• Solid core door: Solid core doors are the most expensive option, and can cost in the thousands. Solid core doors can feature a thin veneer of wood, vinyl or MDF covering a wood pulp core. Some aluminum and steel doors also feature a solid core. Solid core doors weigh less than solid wood doors, but are heavier than hollow doors. They are also fairly effective sound insulators. For customers looking for a tough, durable option that weighs less than metal or solid wood, a solid core door can be a good compromise.

Are There Any Cons to MDF Interior Doors?

Despite the numerous benefits they offer, there are several downsides associated with MDF boards. For one, MDF boards can be easily scratched and, once this happens, they cannot be repaired. This is because the MDF’s external surface is more or less the same as its core, but it is over-compressed, allowing it to act like a sealant. If a contractor attempts to sand it, they will hit the fiber-waxed core, damaging the board’s overall integrity. When solid wood is scratched, it can be sanded down to get rid of any damage on the surface.

Other potential drawbacks of MDF include:

• Vulnerability to extreme heat: Remember that MDF is made from resin- and wax-like compounds. Although it’s made of wood, it can’t be treated the same as wood doors. MDF doors should not be installed near a radiator, heater, fireplace, oven or stove.
• Weight: MDF is significantly heavier than plywood, so care should be taken when transporting or lifting MDF boards. Its density makes it challenging to handle, cut, sand and install.
• Sharp edges: The edges of MDF sheets are very sharp and may slice into fingers if handlers are not careful. Customers who handle MDF are advised to wear gloves.
• Irritating to the eyes and potentially damaging to lungs: Formaldehyde is used during the manufacturing of MDF, and when it is cut, a harmful chemical is released in the form of extremely fine dust, which may irritate the nose and may be detrimental to the lungs. Contractors working with MDF doors should put on a dust mask, or even better, a dual-cartridge respirator. They should also work outside in an area that is well-ventilated.
• Difficulty when working with nail guns: If fastening MDF with a nail gun, there is a good chance the surface will pucker, which leaves a tiny, raised nib at the location of each nail. These protrusions can be removed using a wood chisel or sandpaper.
• Humidity can cause swelling: Exposed edges on an MDF board can absorb moisture, causing it to swell. To minimize swelling, cover the edges with solid-wood edging, plastic laminate, wood veneer or polyurethane varnish.
• Screws can cause splitting: When trying to drive a screw into the edge of an MDF panel door, splitting may result. To avoid this situation, a customer should drive pilot holes first. If they are driving a screw into the face of the board, they should first drill a counter-bore hole — this will allow the screw head to sit below the surface.
• MDF dulls saw blades: Due to MDF’s high glue content, cutting this material will dull saw blades faster than cutting actual wood. To make sure cuts are clean and blades are not quickly dulled, customers should use blades that are high-quality and carbide-tipped.
• MDF cannot handle high pressures: MDF does not have the same strength has natural wood, and when under pressure, it will split or crack. Its life span is also not as long as that of real wood.
• More nails are required: When MDF boards are installed, many nails must be used because the boards’ density is less than that of natural wood doors. The nails must be inserted at close intervals.

MDF vs. Solid Core Interior Doors

MDF and solid core doors are two of the most popular options for interior doors. In this section, we will briefly compare and contrast the two.

Solid core doors generally feature an exterior skin made of molded composite or plywood. On the inside, they feature a wood fiber blend, which makes it feel similar to a door made of solid wood. Solid core doors are considered more durable than hollow core counterparts and provide more noise reduction and temperature insulation.

MDF doors are an engineered wood product, and they have become a much more popular option for interior doors in recent years. While both MDF doors and solid wood doors are durable and relatively affordable, only MDF doors are warp-resistant. For customers looking for a door that provides great sound and temperature insulation, MDF doors are an option to consider. MDF doors feature a smooth, beautiful finish that can be easily painted. MDF doors are also more environmentally friendly because they are made from leftover wood products and sustainable materials.

Browse Our Wide Selection of High-Quality Commercial Doors

At Manhattan Door, we design and manufacture a large selection of architectural-grade interior wood doors. Our door products are all specially crafted to meet the highest standards in the industry and we use high-quality materials, including structural composite lumber cores and either plastic laminate overlay or wood veneer for beautiful finishes.

We have many years of experience applying the most up-to-date building codes, safety rules and manufacturers’ specifications. If you are interested in learning about our interior door products, including wood doors, glass style doors, and door hardware, feel free to browse the selection on our site. If you would like to place an order, get in touch with our staff by filling out our form or calling 718-963-1111​ now. We look forward to working with you!