Finishing Basement – Insulated sub floor question
Hello, thank you for reviewing my question / dilemma. I am in the process of finishing my unfinished concrete poured basement in my 2,550 sqft ranch home built in 2002. Based on the articles within GreenBuildingAdvisor I took the approach of insulating all of my walls with 2″ EPS glued directly to the walls. I am 70% done with this part of my project. I have utilized canned spray foam insulation between the seems of the 4’x8′ panels and tyvek tape. I have fixed all areas where I’ve had water seep in through hair line cracks in the foundation wall in the past. Go figure, after a month of having the insulation secured to one of the walls that has never had any water issues, I discovered a small puddle of water. My plan originally was to glue 2″ EPS from top of floor joist to the bottom of the floor. And for the floor to use 1″ thick rigid foam butted up to the 2″ wall EPS. Plywood over the 1″ rigid foam for my sub-floor. However, here is my dilemma, I have subscribed to the wisdom of having the thermal break and air sealing by utilizing 2″ EPS on the walls, and intended on doing the same with the 1″ rigid foam on the floor, BUT, after seeing the water seep through on a wall that previously never had any water issue I have realized that water is going to come in to the basement in some occasions. So if I did the sub-floor with gluing the Rigid foam directly on concrete basement floor then I am giving the water that gets into the basement through the walls no where to go. If enough water was to come in a particular spot and had no where to go, I suspect the water pressure could increase enough to begin penetrating the seems of the EPS, or even pop the insulation off the wall over time. Or if it does find a way to get above the rigid foam on the floor it would then be very close to plywood sub-floor and could possibly saturate bottom plate of framing. SO my solution that I have come up with mentally is to utilize a dimple plastic underneath the rigid foam, tuck it about an inch underneath the 2″ EPS on the walls. This way any water that comes in through the walls would be directed underneath the dimpled plastic. The little bit of air flow provided by the dimpled plastic would eventually allow the floor to dry or absorb the moisture through the concrete. OF COURSE this goes against the whole wisdom behind air sealing and creating a thermal break on the concrete basement floor ensuring no condensation. But I think this is the only way of ensuring water that occasionally comes in through the walls has a place to go without destroying the finished basement.
What do you guys think? Thank you, and sorry for the long worded question!
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