MDF or Medium Density Fibreboard is a popular building material due to its smooth surfaces and affordability. But can it be used outside? Let’s find out!
Can You Use MDF Outside?
Yes, you can. However, it needs to be either sealed or painted first to protect it against the elements. If you put MDF outside in its raw form then it would soak up water and start to literally fall apart.
So how do I seal it?
There are actually specially made MDF sealers available at a really affordable price. You simply paint these onto the MDF and they help to seal it up to prevent water from getting into the fibres.
This MDF sealer from Rustins can then be further painted or even varnished, adding even more protection.
What about painting?
MDF can be painted with pretty much any paint, but if you want maximum protection then you want heavy-duty paint.
I highly recommend something like Hammerite. Hammerite is a metal paint but it can also be used on MDF. This is a really thick paint that dries incredibly hard and will add long-lasting protection to the MDF.
But this is metal paint I hear you say, how do you know it will work on MDF? Well, I did a really big test on this exact subject, you can read it here: Can You Paint Hammerite on Wood.
The end result of this test was that Hammerite works really well on wood and in particular on MDF.
Here you can see the result of some Hammerite on MDF up against a regular exterior wood gloss. You can see how after 6 months the Hammerite is still protecting the MDF really well and actually doing better than the wood paint!
Moisture Resistant MDF
This is a special form of MDF intended to be resistant to moisture. here in the UK, it is commonly green in colour. Just because this paint is resistant to moisture doesn’t mean you can leave it outside with no protection and it will be just fine.
If you attempt to just leave this outside with no protection it will swell and fall apart just like regular MDF, only it may take a little longer. So again you will want to seal or paint it first.
The good news is that moisture resistant or “Green” MDF can be painted just like regular MDF can.
Another way of protecting MDF so it can be left outside is by using varnish. There are tons of quick-drying, easy to use varnishes that you can paint onto MDF for some instant proteciton.