the_emma•3d agoProlific Poster

Warning: Stop using particle board underlayment near bathrooms

I pulled up a floor last week in a 5 year old house and the particle board under the vinyl was completely rotted out near the toilet flange. The homeowner said there was never a leak, just normal humidity from showers. I measured the moisture content at 18% in spots that looked fine on top. Has anyone else run into this or do you just use plywood near wet areas?

3 comments

3 Comments

wright.leo3d agoTop Commenter

paige166 said "held up way better so far" but "so far" is doing a lot of heavy lifting there. I actually think particle board gets a bad rap for stuff like this, people just install it wrong or skip the basics. If you seal every edge and joint with a good primer before putting it down, it holds up fine in my experience. The real problem is people treating it like plywood when it's a different animal - you gotta prep it right and keep the bathroom vent fan running. Has anyone here actually followed the manufacturer's instructions to the letter and still had it fail?

paige1663d ago

Did you try putting a layer of RedGard or something similar on the plywood before the underlayment? I started doing that after a similar mess in my own place and it's held up way better so far lol.

the_mia3d ago

Yeah but RedGard on plywood can trap moisture if it's not perfectly sealed... kinda risky honestly. I'd rather use a vapor barrier sheet myself, less chance of failure down the road. Just seems cleaner to me.