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There are a few questions about flooding basements in old houses, but I think that all wet basements are wet in their own way, so none of those are helping me.

I live in St. Louis, MO in an all brick house that was built in the 1930s. I believe it is a cinder block foundation. The basement was finished by the previous owner with laminate flooring. When rains really hard OR it rains with a wind blowing against my South wall, water comes in from somewhere and ends up under the laminate. Now, I know I'm going to have to tear all of this up and replace because of mold and mildew issues, but I would like to solve the leaking problem before replacing anything.

The yard slopes away from the house, and I just put in new basement windows. I really don't know how to determine if the water is leaking from somewhere behind the wall under the ground level; if it is coming up from below; or if I need to have the bricks themselves tuck pointed. (I had someone tuck point the home a few years ago before this started; the contractor was a recommendation from a friend and one I would never use again, so he might have done a bad job.) There are no obvious large cracks anywhere on the exterior of the house or in the mortar, but I'm not an expert in brick/foundation work.

Is there a way to establish the source of a leak like this without having to first destroying a bunch of flooring and wall? I know I will be re-doing a lot of the finished part of the basement, but I'd like to know if this will be a few grand for tuck pointing or sealing or 30 grand for foundation work.

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  • Is it brick or block? You mention both. In principle, sealing them both is generally the same, but it's going to be helpful to know which we're dealing with.
    – FreeMan
    Feb 26 at 17:47
  • So above the ground level it is red brick. Below the ground level it is cinderblock. I can see the cinderblocks around the grass line and also in the unfinished portion of the basement. Naturally, that isn't the part that is flooding. Feb 26 at 18:16

2 Answers 2

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Start outside

Your outside is easier to reach overall.

When rains really hard OR it rains with a wind blowing against my South wall, water comes in from somewhere and ends up under the laminate.

Check your gutters. Make sure they flow freely and the water is channeled away from your wall. It's not enough to have them dump near the wall.

Check your weeper system. You'll have to dig down to the footers of this wall. If you have weeping tiles (literally tiles in your case) they may be broken. Replace the tiles with sock-covered ABS pipe. Cover the pipe in gravel. Make sure the weepers are channeling away from your foundation.

Waterproof the outside wall while you're here. There's a lot of good waterproofing membranes you can buy that should limit how much water sits against the wall. Your weepers should take the water from there and channel it away.

If that doesn't work...

I just put in new basement windows.

Check the window wells. Do they drain properly?

This is where you might want a professional (assuming you didn't hire one to excavate your outside foundation). If water is still getting in, it's coming from the floor. You'll need to excavate your basement floor and install collection pipes and a sump pump. Have the pump discharge outside (where it should be channeled away), and not into your sewer system. This job is rough for DIY, just due to all that excavation.

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  • Thanks. The wall where the leak seems to be coming from isn't in the direction of the roof slope, so there aren't gutters there. (Roof slopes east and west; this is a south wall.) But I'll check the ones that do exist for proper drainage. Digging is going to be a bit of a mess because this wall is where my AC and minisplit are as well as a fence, so I might have someone else do that. And for the windows, there aren't really window wells as the windows are actually above the ground line. Thanks for the information here. Feb 26 at 18:20
  • Just as a follow up here, I had a basement company come out, and they noticed that the bottom three or so rows of cinder blocks had been painted with some kind of dry lock. That served as evidence for them that there has likely been a leak problem going back way before I got the house. They suggested a whole basement waterproofing system + pump which they will install through the basement floor. Mar 1 at 15:18
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You need to use process of elimination to determine the source. You ought to investigate the most likely sources first. This is guesswork and I'm going to take a guess. Your question is not amenable to a definitive answer, as you clearly acknowledge in the question. Here I am suggesting a first step that I think is a good bet.

The water is coming up through the basement floor.

My basis:

  • Accumulating underneath the laminate before appearing anywhere else. I would expect some wetness elsewhere if it was coming from anywhere else.
  • Only in heavy rain. I think it's groundwater.
  • 1930s construction. If the basement floor is original, there is no vapor barrier beneath the concrete.

Removing the flooring and some areas of drywall along the bottoms of the outside walls is a good first step. You should be able to see if water is flowing over the surface of the floor from some place to all the wet areas, or appearing everywhere even away from outside walls.

The repair will probably involve perimeter drains, a sump pit, and waterproofing the floor either by destroying and replacing it or by installing a flooring system that is itself a vapor barrier and allows water underneath to drain to the sump pit.

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  • I highly doubt the water is coming through the basement floor—persuming it's a slab. More likely it's coming in between the slab and the block walls, or through the exterior of the walls and dribbling down to the slab.
    – Huesmann
    Feb 27 at 15:28
  • Or through cracks
    – jay613
    Feb 27 at 17:06
  • Well, yes, cracks in the blocks or mortar.
    – Huesmann
    Feb 28 at 12:58

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