How To Waterproof MDF

How To Waterproof MDFs

MDF is a strong material commonly used for furniture, cabinets, and other home projects. It’s also very durable and resistant to moisture. However, MDF isn’t completely watertight.

If you live in a humid climate or near a lake, you might want to consider adding some sort of sealant to prevent water damage.

How To Waterproof MDF

But how do you waterproof MDF? Is it easy to do? Can you do it yourself? These questions race through your mind as you search and search for a solution, but never seem to find the right answers for you. 

So, if you want to waterproof MDF but you don’t know where to start then don’t worry. We have put together this helpful guide to take you through the steps you need to follow. Keep reading to find out more. 

What Is MDF?

MDF stands for Medium Density Fiberboard. This type of wood composite board is made from sawdust that has been pressed together under pressure.

The density of the material varies depending on how much fiberglass it contains. You can use this product as an alternative to plywood or hardwood flooring.

Is MDF Waterproof?

Some people make the mistake of believing that MDF is waterproof by default, which can cause a lot of problems when they try to use the material.

Let me say that again: MDF is not waterproof – it can swell, warp or even disintegrate when it comes into contact with water. 

Once the MDF has been affected by water it will not return to its original shape or condition, so it will need to be replaced. This will cost you time and money. 

Why Should You Waterproof MDF? 

The main reason why you would want to waterproof MDF is that it’s not 100% water-tight. Water will damage the MDF, causing the material to disintegrate and rendering it useless. 

Please be aware that following this method to waterproof the MDF will make it resistant to water, not entirely impervious to water.

You should still avoid using MDF for outdoor projects where the material will be regularly exposed to rainfall or high levels of humidity. 

You can purchase moisture-resistant MDF, MR MDF, which is specifically designed to cope better with moisture than regular MDF.

It is often used in kitchens, bathrooms, boiler rooms, or laundry rooms. It is more expensive than regular MDF but it is worth it. 

If you cannot find moisture-resistant MDF, you cannot afford it, or you already have some standard MDF lying around that you need to use then you can waterproof it yourself.

You will need to add a wood sealant, varnish or stain, or even some moisture-resistant paint. This will allow the MDF to keep out some of the moisture and make it last longer. 

Do not use waterborne polyurethane to waterproof your MDF, as it will not bond properly to the surface of the MDF and will therefore not form a proper seal.

Make sure that you use a primer before you apply the stain to the MDF. 

So, how do you waterproof MDF? 

How To Waterproof MDF

Well, to help you waterproof your MDF, we have a step-by-step guide for you to follow. Just keep reading below to find out more! 

Step One – Get Your Materials Ready 

The first step to waterproofing your MDF is to prepare all of your materials and make sure that you have everything you need to do the job properly. So, what do you need?

You will need to get a latex primer that is suitable for use on MDF. You will also need to choose a water-resistant coating for the MDF- either paint, varnish, lacquer, or stain.

The better it is, the more protected your MDF will be. If you can find a paint that is advertised as 100% waterproof rather than just water resistant then this is ideal. 

As well as the liquids themselves, you will also need something to apply them with. Make sure you have a paintbrush, a paint roller, and a roller tray. 

You will need to wear some old, scruffy clothes that you don’t mind ruining, as the paint or varnish will stain the material. Alternatively, you could wear overalls.

You could also wear goggles to make sure that you don’t get any liquid in your eyes, and gloves to protect your hands. 

It is best to waterproof your MDF outdoors in dry weather, as you don’t want to spill any of the primer or varnish/paint in your house.

If you need to do it indoors due to the weather or not having enough space then ensure you take precautions. 

Prepare the area first by laying a protective sheet on the ground, and open some windows for ventilation as the liquids can have a strong chemical smell. 

Step Two – Prepare The MDF

Before you apply anything to the MDF you need to make sure it is clean. Any dust or dirt on the MDF will get sealed on by the primer. Wipe the MDF down with a cloth to make sure it is clean.

You can also hoover the MDF to remove dirt and dust. If you need to use a damp cloth to remove any dirt then make sure it has been wrung out to remove excess moisture, and let the MDF dry before you paint it. 

Step Three – Primer 

The first thing to be applied to the MDF is the primer. Pour some primer into your roller tray and use the paint roller to apply a layer of primer onto the MDF. Make sure the layer is nice and even. 

Let it dry, then do the same to the other side of the MDF. Use a paintbrush to apply the primer to the edges. While you are waiting for the MDF to dry, wash your roller, roller tray, and paintbrush ready for the next step. 

Step Four – Waterproof

The primer helps the water-resistant liquid to stick to the MDF and form a seal. Whichever liquid you have chosen – paint, varnish, stain, etc- pour some into the roller tray.

As with the primer, apply an even layer to each side and use the paintbrush on the edges. Let each side dry before flipping the MDF over. 

Once the MDF is completely dry, add a second layer. This will make sure the MDF is water-resistant. Once the second application has dried, you are ready to use the MDF. 


MDF is not waterproof, so if you follow this process you can ensure that it is more resistant to water. This will make your MDF last longer. 

Diarmuid Brock

I'm a carpenter by day and an amateur woodworker by night. I don't believe in limitations, and I love to help others. I'm here to answer your questions and make your life simpler. I craft and create with all-natural, reclaimed, and repurposed materials.

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