Thread: Foam In Basement French Drains

I see this so much that I can't decide anymore if all the builders are doing this wrong. Nearly every basement I see that has a french drain still has the foam in place in the space that should be open between the floor and the wall.

This foam is supposed to have been removed at time of construction by the builder, correct?

Anybody? 40 looks and no opinions?? Bueller? Bueller????

Nick, I just looked, and I didn't see an

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This foam is supposed to have been removed at time of construction by the builder, correct?


Or maybe the picture was

I'm not understanding what you are describing - to me (not being in the land of basements - I would think that the walls would be sealed at the floor joint, and any water at that joint would get to the French drain by way of under the floor slab.

A basement where I am would be an indoor swimming pool.

Our house is 23 feet above sea level (better than the 8 feet above sea level we were in South Florida) - our sprinkler system well is only down 25-50 feet, so I am sure water is within a few feet down.

Builders used to remove the foam. When Radon started to become an issue most stopped removing it. Was that the reason or a good excuse? I don't know.

Jerry, up here in our neck of the woods, many basements have what is sometimes referred to as a floating slab floor. The floor is poured separately and has about a 1 inch wide gap between the edge of the floor and the foundation walls around the perimeter of the basement. The premise is that in case water does come through the walls, the gap allows the water to drain beneath the slab instead of running all over it. Water getting beneath the slab can filter back to the sump pit to be pumped out. But in order to create this gap, the builders have to put something in place to act as a form so that when the floor is poured, a uniform gap will be in place once the concrete for the floor dries and cures. They typically use closed or open cell foam to create this space. The problem is that when they leave the foam in place, the gap is full and closed and water that come through the walls flows onto the basement floor.

Mark, I think your take is probably partly correct but I think some of it is still just laziness on the part of the builders.

Originally Posted by Nick Ostrowski

The problem is that when they leave the foam in place, the gap is full and closed and water that come through the walls flows onto the basement floor.

That is how you fill an indoor pool ... er ... basement ...