Identifying cause of basement water leak and fixing it

[Anonymous]

About 4-5 times a year when there's a very heavy rain I can get a small leak in my basement. It's always in the same area and it's never too much but maybe two-three gallons of water when mopped up. But I'm getting tired of it as it's preventing me from doing anything nicer with that basement room. So I'm trying to figure out where the water is coming from. This is the situation:

1930s rowhouse. In front of each house is a wide terrace that takes up most of the width. The terrace is solid and is several feet off the ground. Between each terrace is a small gap that is approximately 2 1/2 feet wide (both sides) that has a small basement window. I'm sure you in DC know the kind of house and set up I'm talking about.

In the basement directly behind the front, the water leak comes through the foundation underneath the basement window on one side. Which means the leak is trickling into the house several feet (at least four feet) below ground level. It is not coming through the basement window well, which generally always remains dry due to the cover. Water never pools on the ground level around the basement window.

The front lawn also slopes gently away from the house towards the street. When we have a heavy rain in a short period, we can get a leak, though it doesn't always happen every time there is heavy rain. It never happens when there's long steady rain.

The other day I was looking at my neighbor's house and noticed their gutter downspout goes right into the ground within a foot or two of the basement window and the site where the water must start leaking into the house. I discreetly tested the soil and found that the gutter does continue away from the house though I don't know how much further away. I don't know these neighbors well.

But do you think it sounds like the reason I'm getting this leak is from this downspout? Or is it likely to just be from ground absorption of water? If so I'm amazed water can leak from 4-5 feet below ground level. And despite a slope that is away from the house! In either case, what could be a good way to stop this leak? Is there anything I can do with the little space in front of the basement window? I can dig into the soil and put in some kind of filler that might help direct water away from the house. Any other ideas? Maybe put up another gutter downspout to mirror the neighbor's though it'd have to go over the basement window?

[Anonymous]

Can you post any pics to help?

Also, is the basement finished or unfinished?

One more, is the water only pooling on the ground, or is there any moisture in the walls or above the area you are referencing? We had a leak one time that was in the roof, but it was hugging a pipe down the inside of the wall and then showing up on a lower level.

[Anonymous]

I know the rowhouse set up you're talking about well. Originally most of them were built w/ the downspout from the gutter going underground in the slope. The houses where there is a small retaining wall at the bottom of the slope have an outlet for the gutter there. You definitely need the neighbor's (and your) downspouts to continue further away from the house. You can buy extenders at lowe's and put them on the end to take the water further down the slope. Ugly but would be an easy fix for that to see if that's part of the issue. Regardless of where the water is coming from, you have an entry point into your basement. Next step is to see if it's coming in the wall and trickling down or coming up where the wall and floor meet (likely) or up in a crack on the floor. Even if diverting the water from the downspouts solves it for now, I'd go further b/c you don't want any entry points. 10 years ago we rarely had these heavy rain events. Now they are becoming common, and will likely only get worse. I'd work with a basement waterproofing company and likely dig down around the front and put dimple board and waterproofing there and then backfill the dirt around the house. I'd also add french drains in your basement and tie them into a sump pump (be sure to get battery backup so it will still work when power goes out). If your basement is unfinished and just a concrete floor, this won't be awful to do.

[Anonymous]

You absolutely want to make sure the gutters are diverting away from the house.

But where I live, that's not enough. We have a lot of ground water.

Do you have a sump pump? Your house may have been built with clay drain tiles, but they could be collapsed or just overwhelmed. The builders would not have intended for the basement to be dry.

Fixing the gutters might be enough to support the drains and keep things steady, but I personally wouldn't finish the basement without digging new interior drains and a sump pump.

You can't seal out the water. You can't make a house a boat - it just won't work. The water needs somewhere to go.

[Anonymous]

Anonymous wrote:I know the rowhouse set up you're talking about well. Originally most of them were built w/ the downspout from the gutter going underground in the slope. The houses where there is a small retaining wall at the bottom of the slope have an outlet for the gutter there. You definitely need the neighbor's (and your) downspouts to continue further away from the house. You can buy extenders at lowe's and put them on the end to take the water further down the slope. Ugly but would be an easy fix for that to see if that's part of the issue. Regardless of where the water is coming from, you have an entry point into your basement. Next step is to see if it's coming in the wall and trickling down or coming up where the wall and floor meet (likely) or up in a crack on the floor. Even if diverting the water from the downspouts solves it for now, I'd go further b/c you don't want any entry points. 10 years ago we rarely had these heavy rain events. Now they are becoming common, and will likely only get worse. I'd work with a basement waterproofing company and likely dig down around the front and put dimple board and waterproofing there and then backfill the dirt around the house. I'd also add french drains in your basement and tie them into a sump pump (be sure to get battery backup so it will still work when power goes out). If your basement is unfinished and just a concrete floor, this won't be awful to do.

+1. This is a good summary of advice.

[Anonymous]

Downspouts should empty 10+ feet away from the house, ideally.

Do you have a sump pump? If water is coming from the ground up, then a sump pump should help. Ours is essential due to a high water table.

[Anonymous]

Fix your gutters.

[Anonymous]

Anonymous wrote:Downspouts should empty 10+ feet away from the house, ideally.

Do you have a sump pump? If water is coming from the ground up, then a sump pump should help. Ours is essential due to a high water table.

If it happens after heavy rains, it's not a high water table. It's rain water finding it's way in.

"High water table" is the unicorn of the basement waterproofing business. 99% of the time water in the basement is caused by rainwater working its way in.

[Anonymous]

Anonymous wrote:

Anonymous wrote:Downspouts should empty 10+ feet away from the house, ideally.

Do you have a sump pump? If water is coming from the ground up, then a sump pump should help. Ours is essential due to a high water table.

If it happens after heavy rains, it's not a high water table. It's rain water finding it's way in.

"High water table" is the unicorn of the basement waterproofing business. 99% of the time water in the basement is caused by rainwater working its way in.

In my DC area neighborhood, water comes out of one of the hillsides for days after it rains. It comes up through cracks in the pavement. I understand that some basement waterproofing guys are scammers and there are places where the geology is different and it’s a non issue, but where I am, I’m fully convinced a sump pump (or a gravity drain) is the only way to have a finished basement.

[Anonymous]

I know that DC rowhouse set-up exactly and I've seen plenty of them that are leaking the exact same as yours. This is ground water that is exerting pressure against the foundation wall at the base where the concrete basement slab floor meets the wall and footer. It's a simple fix with an inside drain along that front wall and it will require a sump pump that can usually be hidden under your basement steps.

Your neighbor's downspout could be a contributing factor but it sounds as if it's a buried downspout that is run under the soil away from the building. Not dumping roof water right into that corner. Either way, the fix is the same.

The best company to call for this in DC is 58 Foundations. Sorry, I don't have their phone number but they will give you a free estimate. Good luck.

[Anonymous]

Anonymous wrote:

Anonymous wrote:Downspouts should empty 10+ feet away from the house, ideally.

Do you have a sump pump? If water is coming from the ground up, then a sump pump should help. Ours is essential due to a high water table.

If it happens after heavy rains, it's not a high water table. It's rain water finding it's way in.

"High water table" is the unicorn of the basement waterproofing business. 99% of the time water in the basement is caused by rainwater working its way in.

Well yeah, it's always rain water unless it's a plumbing leak. But it's not a high water table and no respectful waterproofing company should say so. It's the fact that water is surrounding the foundation walls and footer and no longer draining away through 100 year old clay pipes. So it builds up in the backfilled soil and wants to be the same level in the basement as it is outside that wall. The fix is simple and not too expensive at all when just doing that front wall. The problem is just as common to townhouses built in the last 20-30 years as a century old rowhouse.

[Anonymous]

downspouts are the issue

[Anonymous]

Anonymous wrote:downspouts are the issue

Downspouts are the first thing to deal with. They are a contributing factor, but rarely the whole issue.