I've been in my 1926 house for just over a year, and earlier this week I noticed water seeping in through the concrete wall behind my basement staircase after some intense rain. It was a small but steady trickle. The basement walls have been treated with what I assume is a water proof sealant although I do not know the exact details as it was done before I bought the house, but clearly it was done recently and they could not cover behind the staircase.

What are my options for sealing this up? So far I've only thought up:

  • Rip the staircase out, use something like Drylok, rebuild the stairs
  • Use closed cell spray foam and spray in the gaps (see 3rd photo)

There is no sump pump, and no additional water proofing that I know of. Outside is my driveway and the grading is relatively flat. (See last photo.)

The water came in just to the right of the window, behind the stringer, towards the back of the 5th step.

The water came in just to the right of the window, behind the stringer, towards the back of the 5th step.

The missing riser was broken, so I just pulled it off. (Several of the others are also warped.)

There's gaps all along the edges of the stairs, and the stringer does not appear to be attached to the wall directly.

enter image description here

Blue arrow indicates where the water is coming in, roughly. The gutters deposit water far away from there though.

1 Answer 1


I regards to the unsealed area behind the stairs leaking, you just have to get in there and seal up the unpainted concrete, and also patch any holes, voids, and the gap where the floor meets the wall. We have done quite a few of these by removing a stair tread and in your case the riser so you can get in there.

For materials we always use Hydro-Seal 75 water based epoxy coating and apply two coats and do all our patching with Hydro-Seal 75 epoxy mortar which is Hydro-Seal 75 mixed with Portland Cement & Sand(or concrete sand mix). Hydro-Seal 75 is great for all types of basemant walls and floors

  1. Remove stair tread and riser enough to fit a person in behind the stairs.
  2. Prepare surface by washing with TSP & wire brush after washing if needed.
  3. Mix Hydro-Seal 75 enough needed to coat the area, looks like 1/2 gallon would do this area, and hand to guy behind the stairs.
  4. Paint on with roller and cut edges with brush
  5. Mixer makes some Hydro-Seal 75 mortar and hands to guy behind the stairs with putty knife so he can skim all cracks. Allow paint and patching to dry 2 to 4 hours.
  6. Apply 2nd coat same way to achieve a pinhole free application. I would also seal the entire floor behind there as well after 2 coats on the wall is done.
  7. Put stair treads and risers removed back.

Note- Good job for a small person!

  • Thanks for the advice, unfortunately the stringer for the stairs is really what's blocking me from accessing that part of the wall. Removing the treads and risers will only grant me about a half inch gap to work with. It sounds like I'm going to need to remove the entire staircase to do this right though.
    – zim2411
    Feb 4, 2017 at 19:33

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