Talked to a retired builder at the hardware store who changed how I look at basement floors

I was loading up on drylok at Home Depot in Mississauga last Saturday when this older guy in a work vest just walked up and asked if I was sealing a basement. I said yeah, prep for a reno. He told me most people paint over damp concrete and wonder why it peels in 6 months. He said you have to test with plastic sheeting taped down for 48 hours first to see if moisture is coming up through the slab. I never thought of that simple trick. Has anyone else heard that method?

2 comments

2 Comments

caseyclark6d ago

Not sure I'd take that as gospel. I mean, the plastic sheeting test is a pretty old school trick and it can tell you if you've got a major moisture problem, but it's not really the whole picture. Lots of basements will show some condensation under a tarp just from humidity in the air, not necessarily from water pushing up through the slab. If you tape it down tight in a dry spell and still get puddles, that's one thing, but a little dampness might just be normal for the season. I've seen people freak out over that test and spend a ton on waterproofing they didn't need. Maybe it's just me, but I'd rather use a concrete moisture meter or hire a guy with a calcium chloride test before sealing anything.

noah8386d ago

Have you tried the plastic test during a really dry stretch? I did mine in July when it hadn't rained for like two weeks, taped the plastic down super tight with duct tape around all the edges, and waited the full 48 hours. Underneath was bone dry so I just went ahead with Drylok and some primer first, and it's held up for almost three years now, no peeling at all. But I also had my sump pump checked and made sure the grading outside was sloping away from the house, so maybe that helped more than the test itself.