I'm working on some interior CMU basement walls in my home and I'm a bit concerned about moisture issues. Both sides of these CMU walls are within the basement, meaning there's no direct water exposure from the outside. I plan to attach 1x4 furring strips to one side of the wall to install green board, while leaving the other side as bare CMU (which I'll paint with latex). Given there's an air gap between the CMU and the green board, should I be worried about trapping moisture? Also, would it be beneficial to apply 4mm poly sheeting or drylok paint to the side going to be finished? My basement usually stays dry, but it has flooded before since it's located by a lake. Any advice on managing moisture and preparing for potential flooding would be really appreciated!
3 Answers
I’d recommend keeping the setup mostly vapor open. Just go with your furring strips, drywall, and paint. This way, any moisture can move freely and reduces the chance of condensation issues. Since flooding is a risk, consider using steel studs and a waterproof substrate like Goboard instead of green board, which isn't truly waterproof.
I think sealing it could definitely help. Just try to ensure it’s not totally sealed off so moisture can still escape.
Another tip is to paint the back and edges of the green board with a mold-resistant paint before installation. It can help prevent future problems.
Good point! If I go with green board, I’ll definitely do that. Thanks!
If you've had flooding before, what sort of protections do you already have? Is there a sump pump in place or drainage to one? I suggest finishing with moisture-resistant drywall, but keep in mind that any cut ends will still absorb moisture over time. Green board is just a surface coating, after all. I also recommend installing a wide baseboard and elevating the drywall higher up on the wall to keep gaps above the floor. For baseboard and trim, using PVC is ideal since it's water resistant.
I just bought the place and I'm not familiar with basements, so I’m not sure about a sump pump. Should I look for the lowest point and install one there for any future floods? I've noted your advice about PVC baseboards and keeping them off the floor. Thanks!
Yes, definitely check for a sump rig in the lowest area of your basement! Being proactive will save you some headaches later.
Thanks for the excellent feedback! The Goboard with metal studs does sound like a great option. Since the CMU wall is entirely interior, do you suggest sealing it ahead of potential flooding with paint or drylok? Right now it’s bare CMU, and I’d like to protect it from water seeping in during a flood, or do you think it’ll dry out fine afterwards with some fans?