Can MDF Get Wet & How To Fix Swollen MDF Water Damage

When water finds its way where it isn’t supposed to be, the results can range from mildly inconvenient to full-blown catastrophic. Unfortunately, when it comes to MDF, those results far more in line with the former than the latter.

In this article, we’ll go over the basics of MDF, what happens when MDF gets wet, and debunk some common misconceptions about what you can do if it does, as well as whether or not it can be waterproofed.

Can MDF Get Wet, Is It Waterproof?

Medium-Density Fiberboard, or MDF, is an engineered wood product that is fabricated by breaking down wood residuals into fibers, then mixing those with wax and some type of resin binder before forming it into panels by applying high pressure and temperatures.

This core is then sandwiched between two outer layers, with one being the top surface that will be exposed and the bottom usually being little more than an opposing surface to hold it all together. 

Some MDFs will advertise as being “water resistant,” which refers to the top layer.

Water resistant does not equate to waterproof, however, and over time water can seep through.  Once it does, the core material will soak it up (or any other liquid, really) like a sponge, and when that happens the material will warp, buckle, and distort if it doesn’t dissolve outright like wet cardboard.

While the surface may hold back water long enough to be wiped up if it’s done quickly, the truth is given enough time any amount of water is eventually going to seep in through the cracks in MDF and get absorbed into the core, causing all sorts of problems.

When choosing flooring solutions for rooms with higher risk of splashes and spills, MDF may be a cheap option but it would be unwise to opt for it as opposed to things like tile and the like.  The bottom line is, you should avoid getting MDF wet as much as possible.

Common Issues With Water Damaged MDF

When MDF absorbs moisture, there are several things bound to happen that you’ll notice as it dries.

• Warping

As MDF dries, the boards themselves may twist and contort.  When this happens, they won’t fit together like they’re supposed to, causing uneven flooring and a distinct appearance. 

Once warping occurs, there is no way of restoring the MDF to its original state.

• Buckling

Other times, as the MDF dries the edges might separate from each other and curl upward, in a process known as buckling.  Buckling has a distinct appearance, and is easily identified as such. 

Once buckling occurs, your MDF boards won’t fit together properly again.

• Swelling

Probably the least detrimental of all, swelling is just that; the MDF material swells up when it absorbs water, but doesn’t go back down once it has dried. 

This can cause other issues, but generally speaking you’ve gotten off easy if swelling is your only concern.

• Dissolving material

In some extreme cases, MDF may dissolve entirely when it takes on too much water.  When this happens, the material inside begins to fall apart, much like wet cardboard. 

This literally destroys the inner material, rendering it useless.

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Drying out MDF

There are methods you can employ to dry out MDF, but if they’ve absorbed a fair amount of moisture or water, chances are it’s still going to sustain damage.  That being said, here’s how you go about it.

• Get up as much surface moisture as possible

First and foremost, you should get up as much water from the area as you can.  Mops will be your best bet for surface water, and then towels to pull out as much as you can beyond that. 

It should go without saying, but now would also be a good time to ensure that the source of the water has been taken care of, and isn’t making more work for you.

• Keep air circulating

Using box fans and any other means you may have available, keep the air flowing through the area.  Point box fans directly at the affected area is recommended, as it will help expediate the drying process. 

Generally speaking, though, you’ll want to maintain air circulation, and fans are your best tool in this regard.

• Use dehumidifiers

Another highly effective way of assisting in the drying process is to use dehumidifiers.  Keep them running on their highest setting, and make sure the reservoirs are being emptied regularly so that they continue to run. 

Dehumidifiers will help pull water not only out of the air, but the material as well.  If you have more than one, multiples running at the same time isn’t a bad idea.

• Open windows, when applicable

If it’s more humid outside than it is inside, or if it’s raining out, then definitely skip this step.  But in some instances, opening windows can allow the air to circulate through the room better, helping to speed up the drying process. 

Use your best judgement here, and don’t be afraid to consult your local weather for things like humidity index and the like.

Keep in mind, even when it’s been dried out, MDF isn’t going to return to its original shape.  Due to the nature of the material, there’s going to be some warping, buckling, or swelling at the very least, so it’s best to manage your expectations when going through the drying process.

How To Fix MDF Water Damage

While there are some fixes that can be applied to MDF, they aren’t going to look the best, and the repairs aren’t going to restore full functionality to the item.

That being said, if you’re still intent on repairing a piece of MDF be it for sentimental reasons or otherwise, here’s how you go about it.

MDF Furniture & Kitchen Cabinets

• Dry it out

Before you attempt any sort of repair, you need to make sure the material is properly dried out, or it’s going to fall apart.  Using the methods outlined above, make sure everything is dried out as well as possible.

If the material isn’t properly dried, you not only run the risk of further damaging it, but there is also the likely possibility that things will further warp and contort as they finish drying, at which point any repairs will effectively be undone.

• Sand it down and reshape

Once everything is dry, you’ll need to sand things down to where they’re flush with each other again. 

Something to keep in mind while doing this is that you are removing material as you sand, so you need to be careful and always remember that what’s done can’t be undone. 

Work carefully, watch what you’re doing, and sand down only what’s necessary.

• Fill in areas where necessary

Now that things are sanded down and smooth, there may be some areas that got sanded lower than the others, or where the material crumbled away. 

Using a filler such as a wood putty, apply it in thin layers and feather it out so it doesn’t go on too thick. 

You don’t want to slather on too much, because any excess is going to have to be removed once it dries, and the more there is the longer you’ll be at it. 

Remember, this isn’t going to look like it did before, and it isn’t going to retain its structural integrity, so don’t try to overcompensate with wood putty in that regard.

If you get too much on, scrape it off carefully before it dries, otherwise you’re creating more work for yourself later.

• Re-sand to original shape

Once the filler has dried completely, its time to sand it back down to as close to its original shape as you can.  Again, you’re removing material as you work, so be careful and pay attention as you work. 

Try to get things as smooth as you can, and make sure everything is flush and lines up like it’s supposed to. 

Your goal is to get it as close to its original appearance as you can, but keep in mind you should manage expectations in this regard.

• Apply edging strips

Edging strips are used to finish off unfinished edges of a surface, so depending on how things look when you’re done they may or may not be needed. 

If damage was done to the edge of one of the MDF surfaces, edging strips can help square things up better and give it a cleaner, sharper appearance.

Edging strips are applied relatively easily.  They use a contact adhesive, so once they’re fitted in place they just need plenty of time to dry.  Once they’re dried, you can trim off any excess, then file and sand for a matching finish. 

As before, watch closely as you work, and remember you can always take more off but you can’t put it back on once removed.

Repairing MDF Baseboards

As with other MDF, your best option with baseboards is to simply replace them, as once they’re water damaged they won’t ever be the same. 

But there are some minor repairs you can make to at least get them re-attached and looking a bit better in the meantime.

For swelling, it can be sanded down to match the original profile, or as close to it as you can get.  If there are any dips, curves, or lines, using ordinary hand tools should allow you to replicate the original profile.

Small separations or cracks can be fixed with resin glue using a brush. 

Pits, gouges, and seams can be filled with wood filler and a putty knife, and sanding it back down once it dries.  If you need to replicate lines, fold some 100-grit sandpaper in half, and use the edge to sand them in.

Once everything’s finished, match paint like you normally would, and allow plenty of time for it all to dry.  It won’t look the same, but as a temporary fix it will work.

Can You Seal MDF For It To Be Waterproof?

A common misconception going around the internet is that MDF can be sealed and made waterproof, but in reality this simply isn’t the case. 

Coating MDF in sealant will make the surface more water resistant, but that will only last as long as the coat of sealant does, and only applies to the top layer.

With prolonged exposure to water, the likelihood of water seeping in through the cracks and absorbing into the core material increases.  The coat of sealant will wear off over time as well, and once it does its effectiveness goes with it.

MDF that’s advertised as waterproof or water resistant will have specifications and limits to what it can withstand, so when shopping around make sure you read the specifics as to exactly what you’re buying. 

Given the nature of the materials used to make it, there simply is no such thing as truly waterproof MDF, so make sure you’re choosing the right materials for the right job.

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