I'm considering adding a bathroom to my basement and could use some advice. The basement has about nine-foot ceilings and includes two rooms, one measuring 13 x 20 feet and the other roughly 10.83 x 20 feet. I know the area has high humidity and moisture, so I'm thinking about the following approach:
- Installing 6 mil poly sheeting as a moisture barrier on the bathroom walls and between the rigid insulation and the exterior walls.
- Using 2" rigid foam insulation (polyiso or XPS) for below grade areas.
- Opting for pressure-treated wood or steel studs throughout.
- Going with moisture-resistant drywall for the walls.
- Adding a whole house dehumidifier between the two rooms.
- Building a raised 4.5x8.5 foot bathroom with a sewage ejector pump to deal with the elevation since the house is on a hill.
The sink plumbing setup is intended to make it somewhat of an in-law suite, so I want to keep my options open. What do you think?
3 Answers
Check out upflush toilet systems like SaniFlo! They simplify the plumbing because they can handle multiple inputs from showers and vanities with minimal headache. Plus, the output drain line is only an inch, making it easy to deal with, and the built-in pump can push waste up to 8-10 feet which is ideal for your situation.
Forget about the plastic sheeting; the XPS foam board should act as your primary moisture barrier. Just place it directly against the concrete walls. Use PT wood for the floor and make sure to install bathroom-rated drywall. Don’t skimp on a good bathroom exhaust fan to keep moisture levels in check!
I'd recommend using pressure-treated wood (PT) only for parts in direct contact with concrete, but maybe not for the studs unless you're really worried about mold. With all that humidity, it’s crucial to focus on ventilation before finishing the bathroom. A good exhaust fan and possibly a dedicated dehumidifier could work wonders for moisture control.
Consider using steel studs too! They can be great for mold prevention, just in case.
Thanks for the feedback! I'll definitely make sure nothing is in direct contact with the concrete; I'm thinking of a pressure-treated bottom plate. The two rooms will be heated, so I hope that helps too!