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Community and Q&A

Waterproofing a Basement

Drew_Tozer | Posted in General Questions on

I have a 100 year old double brick house with a concrete foundation and unfinished basement near Toronto. It has some water appearing on the perimeter between the slab and walls. Here are my thoughts: install an interior French drain with a T-pipe that attaches to a radon fan (depressurize under the slab, vent between the joists to the outside). The sump pump will have an air tight lid, the discharge pipe will have a check valve (am I allowed to discharge the sump pump through my main stack into my septic tank?), and there will be concrete installed over the crushed stone over the drain.

Additionally, I’ll install 2″ EPS directly to the concrete wall, build a 2×4 stud wall, add rockwool batts, add drywall, and use latex paint with sill sealer under the EPS/wall. This insulation/wall will be sitting on the French drain, I guess? The basement has partially embedded joists so I’ll caulk around the joists and put expanding foam in the void between the joists for air sealing.

On the outside, I’ll do skirt insulation with a waterproof membrane as an underground roof to keep water away from the foundation and increase the soil temperate to reduce the risk of free-thaw damage.

That’s a big plan. What do you think? Do all of those pieces work together? Did I miss any important details?

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  1. GBA Editor
    Kiley Jacques | | #1

    This is a deep dive into methods and materials that might help inform your decisions: Damproofing and Waterproofing a Basement.

  2. plumb_bob | | #2

    When you pump storm or other drainage water to a septic system, or the reverse, it is considered cross connected and not allowed. You will have to direct your drainage water to either the municipal storm system, or to grade in an approved location

    If you are going to dig up the outtside of the foundation why not install perimeter drainage?

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