Medium density fiberboard, or MDF, is a highly versatile, inexpensive wood product that has many applications, including shelving, cabinetry, furniture and moulding. Made from heat-pressed recycled wood fibers and resin, it is available in laminate, veneer and paint finishes, is very strong, easy to work with, and is less likely to tear and chip. However, if you have a project in a high-humidity area, you must use or create water-resistant MDF, or the material will start to disintegrate if consistently exposed to water and damp conditions.
While it should never be used outdoors or in an application where it’s regularly exposed to water, there are two approaches to “waterproofing” MDF so it can withstand moisture in high humidity areas: use ure Resistant (MR) MDF or make it water-resistant yourself. It should be noted that whichever method you use, MDF is moisture-resistant, not water-resistant, nor waterproof, and is still prone to swelling and warping if in direct contact with the elements.
The first and easiest approach is to purchase MR MDF, which is designed to work well in interior applications where moisture is a concern. Compared to the standard MDF, moisture-resistant MDF is still easy to sand and mill, takes well to most adhesives, veneers and paints, but is made with a moisture-repellent resin. It’s ideal for kitchens, bathrooms, and boiler and laundry rooms, and while a bit more expensive than standard MDF, the moisture-resistant feature makes it well worth the investment.
You can also create waterproof MDF by adding a high quality wood sealant, varnish or stain or moisture-resistant paint so that your project can withstand threats of moisture and humidity. Do not use waterborne polyurethane, as it may not bind readily to the MDF’s surface.
You will need to start with a latex primer, or a primer designed specifically for MDF. Use a 3/8-inch paint roller to apply the primer, and a paintbrush to reach into any areas that can’t otherwise be reached. Let the primer dry for six hours.
Step two is to apply the sealant or water-resistant paint, using a 3/8-inch roller. Use a paintbrush to paint the corners and edges. This layer should take about four hours to dry.
Step three is your final layer of paint or sealant; allow a drying time of at least three days to make the MDF moisture-resistant.
FAQs
How do you make MDF waterproof? ›
You can also create waterproof MDF by adding a high quality wood sealant, varnish or stain or moisture-resistant paint so that your project can withstand threats of moisture and humidity. Do not use waterborne polyurethane, as it may not bind readily to the MDF's surface.
How do you seal medium density fiberboard? ›Sealing MDF with PVA Glue: To seal the edges (or flat surfaces) you can spread or spray a layer of thin PVA (white or carpenter's) glue over the edge with a glue spreader, or a pump spray bottle or air brush, making sure the glue layer is as even as possible, with no build up at the edges.
What is best for waterproofing MDF? ›The only way to make the MDF board waterproof is to paint it. Painting the surface of the MDF board will make it resistant to moisture only if you use moisture-resistant paint, as this type of paint creates a more permanent waterproof layer on the MDF.
How waterproof is waterproof MDF? ›Moisture resistant MDF is not a fully waterproof material- it cannot be submerged in water or used in areas where it would get very wet, like outside in the rain for example. Moisture resistant (MR) MDF is designed to function in humid areas where moisture is present in the air without 'splitting' or 'flaring up'.
What is waterproof MDF called? ›What is waterproof MDF? Water-resistant MDF, also known as MDF Exterior, is an MDF board that is suitable for use in damp areas, both indoors and outdoors.
Is medium density fiberboard waterproof? ›MDF boards are water-resistant to a certain level. But it can get weathered after prolonged exposure making it more vulnerable to moisture. However, there are products on the market that are more resistant to moisture and even fire (exterior grade and interior grade).
What product to seal MDF? ›Sanding sealer is commonly used by cabinetmakers to seal all kinds of MDF. Sanding sealer is nothing more than extra-thick lacquer. It has a dense particle-load that builds quickly on the surface of the MDF to protect it from moisture.
Do you have to seal MDF? ›Sealing MDF Boards Edges
First of all, you should make sure to seal the edges of the boards well. The surfaces also need to be sealed, especially since MDF is prone to moisture, which in turn causes swelling and splitting. Sealing will also be critical if you intend to use water based paints.
MDF is very susceptible to water damage and moisture will cause it to bubble and become swollen.
What is the best top coat for MDF? ›Best Top-Coat for MDF Fiberboards: MINWAX Water-Based Polycrylic Protective Finish. The Minwax Polycrylic Protective Finish is a water-based product and can be applied to any painted or wood surface.
What is the best primer for moisture resistant MDF? ›
Zinnser bin shellac primer, for initial sealing followed by Leyland acrylic primer / undercoat, then two coats of whatever paint finish you want.
Is MDF waterproof once painted? ›Does painting MDF make it waterproof? By painting MDF like any surface, you help to create a film on the surface that can resist some level of moisture. While painting MDF doesn't waterproof it, it does help to prevent water damage.
Can you seal MDF with Mod Podge? ›Either watered down PVA or Mod Podge. Personally, I like the Black Magic Craft method of mixing black paint with Mod Podge so that you create a sealant layer and a base coat at the same time.
Can you use kilz on MDF? ›Prime the MDF with a solvent-based primer, such as Zinsser (buy online) or KILZ (buy online). Avoid water-based primer, as it may cause the wood fibers to swell, resulting in a surface that appears to have a raised grain (no matter how much effort you put into sanding).
Will MDF swell in a bathroom? ›They're not waterproof. Prolonged exposure to water will cause the MDF to swell. For this reason, we wouldn't recommend using MDF skirting boards in a wet room.
Is MDF ruined if it gets wet? ›MDF is very susceptible to water damage and moisture will cause it to bubble and become swollen.
How do you fix wet MDF? ›Water damaged MDF is evident by its bubbles, so sanding it down so that the material is even and smooth is critical. You can choose to do this step either by hand or with an electric sander. Selecting a medium-fine grit, around 100 or 120, is a safe bet. Once your MDF feels flat and even, it's time to paint.