How To Waterproof MDF

MDF is a versatile, strong and affordable material.

MDF can be painted, sanded, screwed and glued to create almost any type of structure you want.

The problem with MDF is that it isn’t fully waterproof, rather it is water-resistant – which means that if you are using it to build something which will be left outdoors in the weather it will rot sooner or later when the damp eventually gets into it.

While you can buy waterproof MDF it is significantly more expensive than standard MDF, it is more cost-effective to waterproof it yourself.

To waterproof your MDF you simply need to coat it with a good quality sealant, varnish or stain, such as:

  • Ronseal Woodstain
  • Epoxy Sealant
  • Latex Sealant

Waterproofing MDF does work, however if any tiny break in the seal occurs and water gets in then it will quickly expand and soften.

Waterproofed MDF is best used indoors or in places where you do not expect it to get damaged at all.

…then follow these steps:

  1. Before you apply the sealant to your MDF you should first prepare the surface.
  2. Sand down any rough surfaces with an electric sander, a palm sander, or sandpaper to smooth down the surface. You should use coarse sandpaper if you need to get rid of any deep scratches first and then progress through finer grain until it is nice and smooth.
  3. Once this is done clean it with a good quality paint stripper to ensure that the surface is clean.
  4. Regardless of which type of sealant you have chosen the application process is pretty much the same. Make sure you are applying the sealant in a well-ventilated place, ideally outdoors.
  5. First apply a thin layer of the sealant to your MDF, using a paintbrush or roller or spray can.
  6. Then you need to allow time for it to dry completely before applying another coat and so on until you have applied sufficient coats as instructed on the product label. We recommend leaving 24 hours between each application.
  7. Once this has been done all that is left to do is enjoy your waterproof MDF!

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