Foam Under Concrete Floor Repair
prairieburner
| Posted in General Questions on
Hello,
I just broke up the basement floor of my 1911 bungalow to add a clean-out for our sewer line.
I’m wondering if there is any reason NOT to install XPS (and poly) in the area before I re-pour. (there is no foam or poly under the old floor)
I figure, even though the are is only around 30 sq. ft. in an odd triangle shape, any added r-value and moisture control is better than none. I have extra 2″ XPS laying around left over from other projects so I’m not concerned about cost.
Thank you!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
David,
No reason I can think of - and way down the road the rest might get retrofitted. Who ever is doing that will thank you.
I see no reason not to add poly. Adding XPS MIGHT result in some extra cracking since the area of the slab you add insulation to may settle differently compared with the rest of the slab. That's the only real downside I can think of. You could mitigate that risk by doing a good job compacting the earth where you're working, and adding some extra control joints at the transitions between the old and new concrete areas. It may also be benficial to use the slightly more expensive 25PSI rated XPS for a little less compressibility too.
Bill