Thread: Sealing mdf edges from moisture

I moisture tested some MDF by leaving it in a bucket of water and after 2 days I could not detect any changes to it which surprised me because the common belief is water destroys it in nothing flat. The MDF was just garden variety from Bunnings so nothing special.

Originally Posted by Chris Parks

I moisture tested some MDF by leaving it in a bucket of water and after 2 days I could not detect any changes to it which surprised me because the common belief is water destroys it in nothing flat. The MDF was just garden variety from Bunnings so nothing special.

Yes, it may be overkill, but I would still like to do it.

I had an experience with hmr mdf where it puffed up and was effectively ruined in just a few hours. I had just finished our kitchen at our last house and I had fit poly coated hmr cover boards to our large kitchen island. When I got home from work my wife said ’the dishwasher hose broke and water poured out before I could turn it off but don’t worry I used towels to trap the water against the island bench’. So it only took about 6 hours for the boards to expand on the bottom 50-75mm which effectively ruined them. They weren’t exactly sitting in water either, it was more damp towels. So there might be some big differences in mdf out there.

Jeez, I hope you're right about this version of MDF. The kitchen here is mdf, and it's terrible.

In any case, I'd probably use Sika Flex Pro to seal the edges. It can be painted. To get a really smooth finish, wear a nitrile glove, dip your finger in Turps and shape it down.

My post was more about how surprised I was at what happened and I did not have any other samples to try in comparison. MDF is supposed to fall apart when wet and we all know that and when it didn't I could not think why not. The obvious answer is the glue used of course but who knows, certainly not me.