Medium-Density Fiberboard in Bathrooms: Everything You Need to Know!

Planning on remodeling or trying to decorate your new home? Medium-density fiberboards (MDF) make great floorboards and paneling material. But you might have some concerns. Can you use MDF in bathrooms? And if so, how? What happens if your MDF floorboard gets wet? 

You’ll be happy to know you can install MDF in bathrooms as flooring or cabinet paneling. But MDF warps and weakens with water exposure, so you will want to properly prime and paint it. 

Still have questions? Here are answers to those and several more. 

Can You Use MDF in Bathrooms?

Most builders will encourage you not to use MDF in bathrooms. But there are cases when the benefits outweigh the risks. Plus, you can take measures to make MDF more water-resistant and suitable for the bathroom. 

How Can You Use MDF in Bathrooms?

You can use MDF as material for your floorboards and vanities in bathrooms. It is a cheap material that is available nearly everywhere. 

Vanities

I don’t recommend using MDF as a material for your bathroom vanity unless you decide it is best for your budget. MDF vanities are more equipped to handle the condition of kitchens, which are drier environments. 

MDF generally doesn’t stand the test of time. So if you’re looking for a long-term vanity, consider other options. If you finish the material correctly, it tends to last longer. But that process can be complicated and comes with its own issues. 

Proper ventilation is also essential. For added protection, use an oil-based sealing product on the back of your vanity. Oil naturally repels water. The two substances have different polarities and thus do not mix. An oil-based sealant will prevent water damage to your cabinets. 

Floorboards

I also don’t recommend using MDF as a material for your bathroom floors. Floors are more likely to encounter water than vanities, so the material is at a higher risk. You may have to redo your floors frequently. 

Although MDF floorboards are cheap, it’s better to invest in a more expensive material that will last longer in your bathroom. But you can still use MDF floorboards in other, drier rooms of your house. 

If you do choose MDF for your bathroom floor, think about buying water-resistant MDF. This product is newer on the market, and builders treat it with extra layers of oil and stains. Sometimes, companies will advertise this material as “water-proof,” which is misleading. All MDF is at some risk of water damage. 

You can also buy normal MDF and finish it yourself.

What Happens If Your MDF Floorboard Gets Wet?

Water can harm MDF floorboards. When in direct contact with water, MDF can warp or swell. The material can weaken over time. After five to seven years, your bathroom floorboards will probably look unsightly. 

Warping is when wood bends after it dries unevenly. Sometimes, when a piece of wood absorbs water, one part dries faster than another. The drier part shrinks faster, which causes the wood to warp. 

Certain factors increase the chance of a wood panel warping. The first is the natural moisture content of the wood. MDF doesn’t have any natural moisture, since it consists of processed wood shavings. But natural wood often does. 

Similarly, the added moisture content is a key factor. Bathroom panels tend to absorb water, and MDF is no different. Some areas of the bathroom floor are more frequently in contact with water than others. Think of the site outside of the tub versus by the sink. So MDF bathroom panels can absorb water and dry at different rates

Still, MDF is a better material to use in the bathroom than solid wood. MDF contains a waxy resin along with its wood shavings that make it more resistant to water. Solid wood does not have this protection, so water is more likely to crack solid wood finishing.  

Is It Safe To Use MDF?

MDF contains a chemical called urea formaldehyde, which is a suspected carcinogen. This chemical is part of the resin that glues the fibers together in MDF.

MDF continuously off-gases this chemical. Before you seal it, MDF releases urea formaldehyde into your home. For your safety, wear a mask and goggles while you sand, prime, and paint MDF. Coat your MDF panels entirely to minimize exposure to urea formaldehyde. 

Likewise, proper ventilation can go a long way in preventing serious side effects. Run air conditioning or temporarily install a fan while you finish MDF.

Urea formaldehyde can have adverse health effects. The chemical may irritate the lungs when inhaled. Exposure can also cause watery eyes, nausea, and difficulty breathing. You may also develop a severe allergic reaction.

Studies show that urea formaldehyde can cause cancer in animals, so keep your pets from MDF until you seal it. It’s uncertain whether this chemical causes cancer in humans. 

Urea formaldehyde is often in wood glue and pressed wood products. For example, particleboard and hardwood panel board plying contain it. But MDF contains the highest gas concentration since it has the highest resin-to-wood ratio. 

How Do You Make MDF Water-resistant?

Stores now sell water-resistant MDF, which is significantly pricier than normal MDF. The good news is that you can fortify MDF on your own. To protect MDF panels from water, follow these directions:

  1. Sand the MDF panels you’ll put in your bathroom. Use a coarse sand grit to create a smooth and even surface. Although it’s tempting to use your hands, use a sanding block. Hands can’t perform perfectly even sanding jobs, but sanding blocks can. Uneven sanding appears more obvious on MDF since its pulp is soft. 
  2. Apply an oil-based primer, especially if the paint you will use is oil-based. Ordinary primers can dry unevenly on MDF, so I recommend buying a special primer for MDF. Apply this primer to the bottom of the MDF along with the surface. This way, the underside will not absorb excess moisture. Consider painting the bottom later, too. 
  3. Wait six hours for the primer to cure. 
  4. Lightly sand the MDF again. Then brush or vacuum debris. 
  5. Dip a rag into mineral spirits and wipe down your MDF. This step may seem unnecessary, but a quality paint job can increase the lifespan of your MDF. The mineral spirits provide a sealed base for your paint coats and reduce grease.
  6. Touch the board to see if the primer has cured. Then apply the first coat of paint. I advise using oil-based paint. MDF absorbs the moisture content of ordinary paint, leaving a dry coat of paint on top. Subsequent coats then only stick to the first layer rather than the MDF. Since the water lies beneath the paint, bubbles can form and ruin your handiwork. 
  7. Wait four hours for the first coat to dry.
  8. Paint the second coat and wait another four hours.
  9. Apply the third coat.

Three coats of paint are standard for MDF. These layers of paint protect the MDF beneath them. Moisture sticks to the paint, rather than soaking into the MDF. Proper priming and painting can make your MDF panels more durable. Watch this video of the MDF priming and painting process for clarification.

You might wonder how to finish the edges of MDF. This task can seem difficult since the edges of MDF are more porous than its surface. But priming them is doable! I have found that covering the edges with wood filler is the best method. Wood filler is a hardening resin sold in home improvement stores that bonds with wood. 

To use, press the wood filler down with a putty knife. Sand the edges. With this extra protection, paint and primer excess won’t ruin your MDF. 

Should You Use MDF in Bathrooms?

Using MDF in bathrooms is an affordable option compared to other wood panels. The material is also pliant and smooth, making it a favorite among carpenters. 

But contact with water can damage MDF. The material absorbs water unevenly, which results in shrinking and warping. MDF rarely lasts for long in wet environments. But if you have a limited budget, don’t worry. Several methods allow MDF to survive in bathrooms. 

You may want to take these measures to make MDF more water-resistant:

  • Use oil-based primer and paint. 
  • Paint MDF with at least three coats. 
  • Cover MDF edges with wood filler. 
  • Ensure proper ventilation. 

MDF can also pose a health risk since it releases urea formaldehyde. Its wax contains this chemical, which scientists consider a possible carcinogen. But you can minimize exposure by wearing a mask and goggles until you seal the MDF. Again, proper ventilation is also key. 

I recommend using MDF in your bathroom only if you’re on a budget. Before you commit to MDF, ensure you can spend the time and energy properly finishing it. Otherwise, you can expect the material to weaken in a couple of years. MDF can be ideal for the short-term but rarely is for the long-term.

However, if you can spend the money and want a lasting product, consider alternatives like plywood or solid hardwood.

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