I am going to attempt to waterproof the basement from the exterior. It is a new development that water is getting in the basement through the window wells and a crack in the wall.

I am hoping I can dig a 18" - 24" deep french drain around this wall and seal the wall with a sealant.

Would this be sufficient?

  • I have found that digging out around the crack during a rain and seeing where the water is coming from is pretty efficient to see what the real issue is. Many yards might be getting flooded from underground streams. Some it is ground level water going down. You have different treatments for different problems.
    – DMoore
    Commented Apr 8, 2015 at 17:36
  • 18-24" may not be deep enough for the drain. It really should go down to the footing and the entire wall sealed from the outside. Commented May 8, 2015 at 20:20
  • it's hard to say given the info provided. Where is the crack in relation to the window? how big is it, how deep does it go below grade and into the wall? This can be an easy fix (by filling cracks in the window/wall) or may be increasingly complicated (grading exterior, sealing exterior wall, etc.).
    – aaron
    Commented Jul 8, 2015 at 4:29

2 Answers 2


If the crack is visible from inside, you could use an expanding polyurethane foam kit. I've used one from RadonSeal in the past (http://www.radonseal.com/crack-injection/diy-injection.htm) and had great results. You can also inject the crack from outside if that's easier. I'd also check grading (is soil sloped away from the house?) and drainage (no close downspouts, etc) outside to make sure any easy water sources are taken care of.

  • Do all of this but make sure you check the drain tiles in your window wells. Those are tied to your sump pump if you have one or any drain tile that works with your house.
    – Dano0430
    Commented Jul 8, 2015 at 6:11

A French Drain will not be that helpful for your situation for a couple of reasons.

  • French drains allow water to stay in a "hole" until it can percolate back into the soil.
  • There is a crack in your wall. Even if you fix this the soil will be very wet near the drain for more time than normal.
  • As your French Drain seeps water back into the soil the saturation level of the soil will increase. Once the soil is fully saturated the only thing that rain (or any water) will do is flow on top of the soil. (Called sheet flow). Depending on the grading this additional water could end up right back in your window well.

Your best bet is to install a sump pump of sorts. If your plan is to waterproof your exterior then take this time to lay some gravel and drain tile at the base of your basement wall. Then use your sump pump to get this water far away from your house. (At least 10ft) If you can't do this then consider consulting an engineer to help design drainage around your house to make sure that the water flows away from your house quickly.

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