Closed Cell Foam on Rublestone Basement – Zone 5A
Hello,
Here is the scenario: Zone 5A with a basement 7′ high, there is NO bulk water issues as the exterior grading diverts the water properly. The basement does NOT have a sump pump. There are some minor water drips here and there but not to the level of accumulation. Plan is to point major looses on mortar and clean the walls for Closed cell foam ( I’ve read this is a good practice). While doing so, a new concrete floor will be installed.
Questions are: Any recommendations on this approach? Also, would a perimeter drain be necessary? Do I need to add some drainage mats at the bottom of the walls prior to foam? (I assume this goes with the perimeter drain)
Thank you,
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Replies
How damp is your basement floor? If you have a sump pit, is the water ever close to the surface? Is your exterior stormwater and groundwater well-managed? How long have you been monitoring conditions?
The safest approach would be to assume the walls will leak heavily at some point--late winter rains are a common problem, when the ground is frozen except next to the foundation--so it would be safest to include a dimple mat or other drainage system over the entire wall. At the floor, if you don't already have an interior drainage system, it's always a good idea to provide a backup system there as well. And of course it's important to include a vapor retarder under the slab, and ideally some insulation as well. But if your site is well-drained, you aren't storing anything in the basement so a minor flood every 5-10 years would not be a disaster, and you have humidity-controlling devices in your living spaces, you can eliminate some of those items.
Thank you Michael,
We have been living here for 12 years. The floor is not damp. We do not have a sump pit and exterior strormwater is well-managed. I was planning on Close-cell around the perimeter and new concrete floor/slab. Since the is no bulk water coming form the wall, I fell that a dimple mat won't be needed? Would the sequence be Spry foam and then "lock " the foam at the toe of the wall with new concrete floor? See attached for what I have on my drawings.
You probably don't need the dimple membrane then. I would still insulate under the slab if you can spare the headroom, and you definitely want a heavy-duty, sub-slab vapor retarder, even if the floor appears to be dry. This is also a good time to include a radon mitigation system. You can do foam or slab first.