If your home has a lot of medium-density fiberboard, you may wonder how best to care for it. Or maybe you are starting some awesome DIYs that use medium-density fiberboard and you are wondering how to know what kind you’ll need. Is MDF waterproof? Is MDF moisture-resistant? If you are concerned about keeping it safe from humidity and moisture in your home, read on for some helpful tips and ideas.
What is MDF?
Medium-density fiberboard is engineered wood made of wood by-products like shavings and sawdust. It is held together with resin and then heat-pressed into flat panels. It is usually considered an upgrade from plywood, but not quite as nice as real wood. MDF has a lot going for it!
This product is commonly used in homes for cabinets, wainscoting, furniture, doors, door frames, and sometimes even flooring. While MDF is never fully waterproof, you can purchase MDF that is water-resistant or moisture-resistant, and even regular MDF can be made moisture-resistant fairly easily.
Benefits of MDF:
- MDF is dense and will not warp
- It is considered an eco-friendly product since it is made of wood by-products and can be recycled
- It is easy to drill, cut, and glue MDF, making it a fairly easy material with which to work
- MDF has a smooth, easy-to-paint surface. It can give you the look of real wood for a fraction of the cost.
- Whereas real wood cabinets require sealing and oiling to keep them looking their best and can expand and contract with changing temperatures, MDF cabinets are low maintenance and sturdy. MDF cabinets can last 25 years or more with a little care.
Drawbacks of MDF:
- It is very heavy
- Because it is made of many fine particles glued together, it doesn’t take screws very well
- It cannot be stained–it just absorbs the stain. And because it has no wood grain, the stain wouldn’t look good anyway.
- When it is cut, it releases a lot of very fine dust into the air. You need to wear a safety mask when using a saw on MDF.
- MDF can release small amounts of formaldehyde gas, although sealing will mitigate this.
- Untreated, MDF will absorb water and swell
Water Resistant MDF and Moisture Resistant MDF
While MDF isn’t waterproof, there are two levels of water resistance available. Water-resistant MDF (known as WR MDF) can be used outside for things like outdoor furniture, signs, or kids’ play equipment, or even indoors in the bathroom or kitchen. It’s made with water-resistant resin or glue, and it is formed with more pressure than regular Water-resistant MDF is generally more expensive than regular MDF and is usually distinguishable from other types of MDF by its dark brown core.
One step down from moisture-resistant MDF (sometimes called MR MDF), which stands up to moisture in the air and environment better than regular MDF. If you plan to use MDF for bathroom cabinets or wall panels, you really want moisture-resistant MDF, if not the water-resistant type. Moisture-resistant MDF is often colored green, to distinguish it from other varieties. It is not hard to find places to buy moisture-resistant MDF. It is widely available at stores like The Home Depot and others.
Whatever type of MDF you use, you should make sure to apply primer, moisture-resistant sealant, or varnish to any cut edges or unfinished surfaces. This is necessary to make your MDF last. Any exposed edges or surfaces will absorb water and humidity, at least to some degree.
How to Moisture-Proof Your MDF
If you’re using regular MDF, you can increase its moisture resistance with a little elbow grease. Apply several coats of moisture-resistant wood sealant or varnish, paying special attention to the edges. Do not use a waterborne polyurethane, because it won’t bind to the surface of the MDF. Allow each coat to fully dry before applying the next one and be careful to avoid drips.
Next, choose moisture-resistant paint. Apply at least two coats, allowing the paint to dry in between. Make sure to cover all edges completely. If you need to make cuts or use nails or screws, make sure the newly exposed edges or holes are sealed as well.
How to Repair MDF If It Is Water Damaged
When MDF absorbs humidity or water, it swells and the layers split. It’s possible–although a little tricky–to repair damaged MDF.
- First, add a shellac-based primer to the damaged areas, making sure to really get it down into any cracks. Use a small paintbrush.
- Then use plastic wood filler and a putty knife to seal up damage. Make it as smooth as possible, and allow the filler to dry completely.
- Sand any bubbles and rough areas, and the putty, so the surface is smooth and even. Sand by hand or use a sander, and use medium-grit paper. Make sure you wear a mask!
- It may take a few rounds of puttying and sanding to make the surface smooth and even.
- Add a few coats of primer undercoat, and then paint with moisture-resistant paint as desired.
A Few More Tips for Using MDF
MDF is easy to cut, but because of its density, it can dull your saw blade more quickly than other types of wood products. Make sure you have a few extra blades on hand! And remember that it does release a lot of dust when cut or drilled, so use a mask for safety.
When cut, the edges of MDF boards will be a little rough. Make sure you sand them down and paint them with sealant or solvent-based primer (not water-based). After the primer is dried, sand the edges and wipe off the dust. Then you can paint as desired.
Summary
Remember that while MDF can be purchased or modified to make it water and moisture-resistant, it’s not a waterproof material. Try to keep it from contact with water as much as possible. Make sure all edges and any cuts are sealed with primer and paint. With a little care, your MDF cabinets, wall trim, doors, and furniture will serve you well for many years.
