# Basement: XPS Insulation and Slab Reliefs



## Windows on Wash (Aug 30, 2011)

Do you have a picture? Might be an expansion joint.


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## Subliminal (May 31, 2012)

Basically, when I had the contractor come in and pour the flood I had him:

put perforated hose under the floor in 4 inch of clean stone, leading to a sump pit that has a below grade output in the woods (gravity fed). Then, I was still worried about possible moisture, so he put a ring a 2x4 around the walls and poured the floor...which then left a 1.5 inch relief all the way around..so if water WERE to come through the walls, it'd go into that relief channel.

It's kind of hard to see, but this is the best photo I could find:

Image: https://www.dropbox.com/s/qmz2562rpj0293x/2012-02-21 15.07.53.jpg

I'm in NJ, so I have a substantial amount of moisture in the air, and run a dehumidifier in the summer...but when I finish this room off, I'm trying to (obviously) keep it as dry as possible. ;-)


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## Windows on Wash (Aug 30, 2011)

In this case, if you are worried about wall moisture infiltration, you need to leave and area for the wall to drain from behind the foam board but still block off that area from room air to limit any radon or moisture/humidity.

What size foam are you going to use?

If you were going with 2" foam, I would run the foam right tight to the floor and seal the connection between the floor and the foam.

Make sure you glue in vertical strips to allow the water to drain out.

If you are going with 1" foam, you may have to rip a strip of foam to glue to the bottom of the board to seal off the slab to foam board connection.

By the time you rip it down and all the other hassle, 2" might be easier and more time effective.


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## Subliminal (May 31, 2012)

Roger that! Thanks for the replies. I'm actually no longer worried about water getting in...as with many things, hindsight is 20/20 and I wish I had never had those reliefs cut.

What would one use for sealing the floor/foam connection? And would one seal at the top of the wall as well?

Thanks again!

damon


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## Windows on Wash (Aug 30, 2011)

Any good compatible sealant will work.


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