What are French drains good for?

[dr.girlfriend]

Our neighborhood has a Facebook group, and after the recent heavy rains there was a post asking how a lot of people were doing.  Several people were like, "We have a French drain, so it was fine."

Our house is old (built in the 1950's).  It has an unfinished, dirt-floor crawlspace under the kitchen that is maybe about five feet tall.  There's a square opening that opens into our main basement which is about four feet lower.

We have a sump pump in the main basement area.  In a really heavy rain, though, water comes STREAMING through from the crawlspace.  I think we had someone look at it once and they said it was just seeping through the stone walls and there was nothing to be done, but I have trouble believing that, because it really doesn't seem like a slow seep, it is like a small river.  Yet I can never tell exactly where it is coming from.

By the next day the basement is pretty much dry again and it must soak through the dirt floor of the crawlspace because even inches of water in there is gone by the morning but I'm worried that this is causing damage to the foundation, or mold to grow, or something.  It can't be good, right?  Is this the kind of thing a French drain would help, or if it's really coming through the walls would that not matter?  We did have spray foam insulation sprayed all around the walls of the crawlspace but that doesn't seem to have mattered (and we weren't doing that to waterproof, obviously).

[simpsongal]

A lot of my neighbors have them, some in combination w/sump pumps (esp the split level houses w/lots of below-ground living space). In your case, a french drain would be designed to take the water from your house and crawl space to an underground "dry well" buried in another location in the yard.

I'd probably look into it again, the amount of water you're describing doesn't sound good for your foundation.

[definitelyO]

in our case the French drain was good for nothing. I mean I know how they work but never did for us - not sure if it wasn't put in right or not.

we are on the down part of a neighborhood slope and have had multiple water issues in our finished basement. (1957 home)

in our case we had to put in a whole basement system that included jack hammering up the entire perimeter of the finished basement and installing internal drains and 2 sump pumps.

I'd probably have someone out to take a look and get a few estimates/ideas of what they think it is and what could help.

[archiethedragon]

The title sounds like the beginning of a Jerry Seinfeld bit.

What are French Drain good for?
And why do they call them French Drains, anyway?
Do they come with a baguette and stinky cheese>
Do they kiss you with their tongue?
Do they get installed with a maid's outfit?



Hmmm.. come to think of it, maybe I don't do a great Seinfeld....

[aspentosh]

We have a French drain under our entire foundation, and it pulls all the water into the sump pump for expulsion. We also have a crawlspace, but ours is NEVER wet even in big rains. We have a waterproof barrier down to keep the damp ground covered, but no water spills into our finished area. So our setup is veeeeery different it seems.

We also looked at getting them extended out, and maybe doing a dry well so our sump pump doesn't just pump all that water onto our grass and make it even soppier. (Our contractor recommended actually something different, so we won't...)

[ellipses84]

It just routes the water away from the house (or to a location you want, like a pump). If it isn’t designed correctly or you get so much rainfall / sitting water, it won’t work as intended. Sloping the ground away from the house will help too. Is the dirt under your crawlspace depressed and filling up with water like a pool or puddle before it floods through the basement wall? Or is the ground absorbing the water pretty quickly? If it’s pooling under there, you could add more dirt / rocks to direct the water away from that wall, almost like a little stream that ends at the edge of the house away from the basement. It’s possible you’ll need to do more, like a French drain and / or re- waterproofing that entire wall.

[starburst604]

Would you believe that we have one in our home yet we have no idea how it works? We are at the bottom of a hill and based on PP I get why the previous owners installed it. When we have a fierce rainstorm water just comes barreling down the hill and upsets all our mulch
Into weird crop circles. Now I’m so curious about where it is and where it routes the water to!

[k3am]

We have two French drains under the house that are intended to lead any standing water towards the sumps. Couldn’t say with any certainty since basically the day we installed them, the state went into a record drought. Screw you, Murphy.

[dr.girlfriend]

Sept 3, 2021 22:57:46 GMT -5 k3am said:

We have two French drains under the house that are intended to lead any standing water towards the sumps. Couldn’t say with any certainty since basically the day we installed them, the state went into a record drought. Screw you, Murphy.

I swear I stared at this post for quite a while before I realized you were talking about Murphy's Law.  I was thinking you were blaming Governor Murphy (the governor of New Jersey) for the weather, like he caused a drought.  And then also wondering WTF because New Jersey got crazy hurricane weather just last week.  Maybe I should go to bed.  ;-)

[fryjack2]

Sept 3, 2021 12:33:17 GMT -5 definitelyO said:

in our case the French drain was good for nothing. I mean I know how they work but never did for us - not sure if it wasn't put in right or not.

we are on the down part of a neighborhood slope and have had multiple water issues in our finished basement. (1957 home)

in our case we had to put in a whole basement system that included jack hammering up the entire perimeter of the finished basement and installing internal drains and 2 sump pumps.

I'd probably have someone out to take a look and get a few estimates/ideas of what they think it is and what could help.

Tell me more about your basement system. 

Our house is also from 1957, multiple levels of living (including 3 basement levels that are a few steps apart), and our backyard slopes pretty decently towards the house. 

We have owned our house for 3 years, and have never had water in the basement.  The previous owners were here for more than a decade and said the same. We had a water assessment before we bought and they said they didn't see evidence of water.  But there is clearly a panel in one of the rooms we use as a gym in the basement that looks like it was taken out and rebuilt and the walls in that room are painted concrete ( I think) with what looked like some efflorescence ( we think that's what it was) on the walls that abut the outside world.  We had the walls in that room painted with a waterproof barrier. 

Our garage was getting damp on the floor at the wall that abuts the gym.  The gym is a step up from the garage level. We had someone come out, took down that wall and rebuild it with steel bottom and waterproofing, etc. because the wood inside was original and decaying.  Over the last month of crazy rain, I noticed there is dampness at that same spot again. Super frustrating.  The gym floor is a hard tile.  The moisture gauge tool did detect higher than normal levels at certain parts along the walls in that room, but never had any water come in, which is why we redid that wall.   

We also had a different room in the basement ( abuts the garage on a different side and the front yard below grade on another) get some buckling of the plaster wall.  We had the wall rebuilt with waterproofing barrier and now run dehumidifiers 24/7. Which we hadn't done and should have been doing.  

I think our basement smells musty in some areas.  H doesn't smell it as much as I do. Maybe the couch in that small room absorbed the mustiness. Its just so annoying to me. 

We do not have a sump pump.  We did install a small drain in our backyard because we had a bunch of bushed removed and the area that they were in tends to get standing water after heavy rain ( its the flat part of the slope).  It has only seemed to marginally help with the yard.

I guess we could do a huge dig up of the yard and do a perimeter drain system, but I'm not sure how much good that would do since we don't actually have water in the basement that we have ever seen.

I'm just not sure if its old house basement or if there is something more serious we should be addressing.  Everyone we have brought in thinks its fine as is, but we could do a $$$$$ exterior drainage system if we wanted.  Super helpful.  Ha.  

[redheadk]

We have French drains but it doesn't sound like we use them for the same purpose. We have clay soil here and no basements. We also get hard/intense rains. Our French drains just direct water from our backyard out to the street since our streets are designed to collect water. They work great and move water away from my backyard so that my house doesn't flood from rain water. We have 4 drains on 2 lines, one line on each side of the house.

[SusanBAnthony]

Our first house has an eloborate system designed and installed by the previous owner because the basement got wet. It didn't work at all. We spent years regrading before eventually installing drain tile.

In theory french drains work, but only if they are installed correctly.

We should have just installed the damn drain tile in the first place instead of spending years trying to fix it the cheap way and mopping up water.

[simpsongal]

Sept 5, 2021 15:53:21 GMT -5 SusanBAnthony said:

Our first house has an eloborate system designed and installed by the previous owner because the basement got wet. It didn't work at all. We spent years regrading before eventually installing drain tile.

In theory french drains work, but only if they are installed correctly.

We should have just installed the damn drain tile in the first place instead of spending years trying to fix it the cheap way and mopping up water.

ive never heard of drain tile - can you explain?

[SusanBAnthony]

Sept 5, 2021 17:37:25 GMT -5 simpsongal said:

Sept 5, 2021 15:53:21 GMT -5 SusanBAnthony said:

Our first house has an eloborate system designed and installed by the previous owner because the basement got wet. It didn't work at all. We spent years regrading before eventually installing drain tile.

In theory french drains work, but only if they are installed correctly.

We should have just installed the damn drain tile in the first place instead of spending years trying to fix it the cheap way and mopping up water.

ive never heard of drain tile - can you explain?

Wow who knew even drain tile was regional lolol.

It is basically a french drain around the perimeter of your basement or crawl space, but it's IN the house. It's is often put in in new construction but you can put it in an existing basement as well (which involves jackhammering 6" of concrete around the entire basement floor) for maybe 10k. The drain tile collects water that comes in and routes it to the sump pump in one corner of the basement, and pumps it out to your front yard.

They are super common in the Midwest. It's basically easier to let in the water that wants to come in,and pump it out, than it is to waterproof a basement. but it won't help with water coming in through a basement window for example.

[ssmjlm]

We had 2 put in at our old house, but they were for landscaping. No clue on ones inside the house.

Ours were to direct standing water away from the end of our driveway back to the creek in our backyard. They worked really well.