How to fix a leaky basement
June 25, 2008 7:18 AM   Subscribe

Should I fix my leaky basement from the inside or the outside?

My basement: it leaks. What follows is plenty of detail, since I now know more about basements than I ever wanted to.

I've now had three contractors come to view it, and they're giving me contradictory advice: two say fix it from the outside, that works best, one says inside is the way to go. All three say I need weeping tiles. Two say they will put them on the outside of the wall, and apply a membrane, one says they should go inside.

The details: We live in a pretty old house (80+ years, as far as I know) with what looks like a stone rubble foundation. The parging is coming off the walls on the outside, and I can see that the foundation is damp. Inside, there's actually not much water, but the walls are damp and there is some water on the floor. Not much, but this hasn't happened before, and I suspect it will only get worse: we've have spectacular amounts of rain in Toronto season, and I believe there's more to come. One window frame has rotted wood, and needs to be replaced.

The complications: The basement is finished. Fixing it from the inside means we'll have to remove the drywall and part of the floor. If we go from the ouside, we have to dig up a concrete walkway and then replace it (it's a shared walkway and our neighbors will not look upon us favourably if we don't replace it).

I'm still struggling to understand what will work best/longest/be best for the house. If we fix it from the inside--isn't the water still penetrating the foundation? Isn't that bad? If we fix it from the outside, are we risking damaging the foundation in some way? (I've read that you should leave a stone-rubble foundation alone).

Do you have any experience with this? Any advice? Fixing this is going to be really expensive either way we go -- we can only afford to do it ONCE.
posted by Badmichelle to Home & Garden (11 answers total) 2 users marked this as a favorite
We had a somewhat similar problem with a slightly different house-- walls are brick inside and out, basement is unfinished (this makes the fix way easier, so sorry). We were having serious problems with seeping-- actual floods from water just seeping in through the brick.

First fix was amazingly easy-- we planted heavy ground cover around the walls, and fixed the roof gutter. Turned out it wasn't really attached, so all the roof runoff was just streaming down the side of the house and saturating the ground, which had meager plantings, so the water was just soaking into the house. This took the problem from flood to seep.

We then tuckpointed inside *and* outside, which completely stopped the problem. You have a tougher problem because of the close-in walkway. When you redo the walk make sure it is canted *away* from the house so that water doesn't seep through the ground into the basement. Have fun! Ain't home ownership a blast!?
posted by nax at 7:29 AM on June 25, 2008

Thanks, Nax. Actually, I forgot to mention that fixing the downspouts is step #1, which we're going to do no matter what (one of the downspouts has broken off, and water is pooling right next to the house).

If we go with the outside fix, we'll definitely make sure the walkway is sloped away from the house.
posted by Badmichelle at 7:54 AM on June 25, 2008

Been through this twice - with my house and my father's. If the ground around your house is sloping towards the house you need to change this because no waterproof membrane will permanently solve the drainage issue. Fixing the downspouts - and adding extensions which drain further away and downslope may be enough. You may need to additionally change the slope and add a tile field.

My father's house is built into the side of a hill so he needed to have the landscape around the house changed to direct drainage around the side of the house instead of directly towards it. He opted to also seal the basement (internally) and fix downspouts. No more problem but definitely a pricey fix.

Have any of your contractors measured the slope around the lot? Without knowing that aspect of your situation you don't really know enough to decide what you're going to have to do.
posted by leslies at 8:48 AM on June 25, 2008

With a stone rubble wall I really doubt if you could do anything inside to keep water out.
When the basement was finished, it was obviously dry enough at the time, so the problem is outside, not inside.

I would take a stepwise approach rather than immediately going with the dig it up outside approach. See what the effect is for each step and then go to the next one only if you still have a problem. First, obviously fix the downspouts and get all roof water directed well away from the house. Then, check grading all around the house. The surface should clearly slope away from the house all around. If possible aim for a six-foot sloped perimeter all the way around. Planting groundcover on that is a good idea, it will solidify the soil and help direct water away. If the concrete walk is properly canted to direct water away from the house, leave it alone, and just point the stone above the walk. Particularly, seal the crack between the walk and the house, that's where water gets in, not through the wall above. If the walk abuts your neighbors's house also, they should do this also, or water will still get into the ground in that area. Consider the costly fix of installing weeping tiles only if all of the above does not dry things out sufficiently inside.
posted by beagle at 8:59 AM on June 25, 2008

Definitely fix the downspouts and landscaping first. Then observe the basement after some heavy storms to see if this doesn't fix things. Another possibility is using sheets of polyethyene along the foundation walls to keep the runoff from going straight down the foundation wall.

But, if neither of those things work, due to a high water table or poorly draining soil, you'll get the best results from the outside fix. The most common reason people don't do this is that it's much more expensive, but if you have to replace the interior finish it could be worthwhile. How do the estimates compare?

Here's how it should go:

1. Contractor excavates a trench around your foundation. Not the whole foundation all at once, but small sections so that most of your foundation wall is still supported by soil.

2. Contractor applies a asphalt based membrane to your basement wall using either spray or brush.

3. A perforated PVC pipe wrapped in filter fabric is buried at the foot of the foundation wall.

4. Drainage board is applied to the foundation wall (Mirafi is a common brand).

5. Wall is backfilled with free draining material, such as crushed stone.

6. Repeat for next section, connecting the PVC pipe together as you go. The discharge from the foundation drain should empty well away from your house.

A couple things to ask the contractor for:

1. References. Make sure he has experience working with rubble foundations. Call his references and ask specific questions, like "Have you had any further problems?" "Was there any cracking or settlement issues?" "Did the Contractor have to do additional work to fix the problem after the initial work was completed?"

2. Liability insurance. If someone is excavating around your foundation, there's a possibility that your house could collapse. Get a copy of his insurance certificate and read the contract carefully to make sure you're covered.

3. Guarantee. Get a guarantee in writing that the work will fix your water issues and that the Contractor is responsible for any additional work necessary if it isn't fixed.

You should document your current issues in writing and take lots of pictures of the interior and exterior of your house before having the work done. This includes upper story walls that could crack or shift as a result of foundation damage.
posted by electroboy at 9:03 AM on June 25, 2008

Again, thanks for the advice. Unfortunately, there's only about two and half feet between my house and the neighbor's (houses in this area tend to be pretty close together), so a six-foot sloped perimeter isn't in the cards.

I'm going to ask the next contractor about doing something on top of the existing walkway to create a slope/seal out the water. There really isn't much water in the basement at all at this point and now that I think about it, I wonder if it's being caused by that cement walkway (which has only been in place two years - a previous [horrible] neighbor put it in).

Leslies, if you come back to this post, what is a tile field? What I've found googling suggests it has to do with septic systems.
posted by Badmichelle at 9:14 AM on June 25, 2008

Sounds like you need an exterior "french drain" which is what electroboy describes. This will help immensely. At least it did in my 1904 bungalow with a brick foundation.
posted by zpousman at 9:48 AM on June 25, 2008

Here is a good explanation. The site is a commercial business which I know nothing about but there explanation of drain tile is one of the clearer ones I've seen - hope that helps.

The perforated pvc pipe electroboy refers to is drain tile.
posted by leslies at 10:09 AM on June 25, 2008

Maybe you and your current "good" neighbor could agree to just get rid of the cement walk. Putting something on top of it would be difficult to adhere and would crumble off. What that walk is doing is channeling water into the crack between the cement and the wall. Before the cement was installed, there was probably a natural depression in the middle, from walking through, that channelled the water out from between the houses, and somehow you need to restore that.
posted by beagle at 10:59 AM on June 25, 2008


The walkway might be an issue, but since she hasn't posted pics, you can't say that it's causing the problem. There are also repair mortars designed for thin applications that are appropriate that won't have adhesion problems or crumble off.
posted by electroboy at 11:56 AM on June 25, 2008

As it turns out, the water in our basement was coming from a leak in the water heater NOT a leak in the basement. (!)

My advice - try to get an objective opinion on your basement situation from someone who isn't trying to sell you an expensive solution (some of the advice here was great, though).
posted by Badmichelle at 7:05 AM on December 17, 2008

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