Flooding basement - what do you know about French Drains?

[Mindy Jensen]

My neighbor's basement is flooding after some pretty heavy rain over the past week. They have called a basement guy out, who would solve the problem by jackhammering up the cement floor in the basement, digging a trench and installing a French Drain that goes into a sump. Has anyone done this before? Did you have success? Do you know the benefits of interior vs. exterior french drains?

Thanks so much.

[Edward Debbs]

On two different houses we've had either an indoor system or an outdoor drain.  The fix depended on the property.  If you have a high water table you'll probably need an indoor system anyway.  Sloped back yard?  Probably an outdoor system.  Our indoor system choice as also influenced by having to jackhammer up a large concrete patio in the back yard too.  Cost difference was probably going to be 15k.  

One thing I can say is that I liked the results from the outdoor system more.  Both basements are dry.  The indoor system one is still more humid however, because even though the water is managed it ultimately does get in.

[Joey Wharton]

I am doing this to a property I purchased in January. I had drainage engineers, structural engineers, foundation specialists, GC's, etc. look at the problem. It started when he snow started to melt. Did endless research. Luckily the basement was gutted for a structural repair. We had EXTENSIVE (possibly record breaking rain) these past couple of weeks. Many people in the area are flooding badly. They saw my guy doing the work and us being one of the only houses dry (and at the lowest worst point for flooding) so now he's doing other people's houses. 

MAKE SURE YOU HAVE A DRAINAGE EXPERT ON IT. I had so many companies bid outrageous prices and after getting advice from the true experts with no conflict of interest, turns out those companies who send out an estimator really don't know what they are doing and can possibly do more damage.

I feel 100% confident that we can build out the apartment downstairs without issue now or in future.

This is what we had done:

Interior perimeter 4" drain perforated with sock

trench dug at a pitch to ensure proper drainage to sump - THIS IS KEY!

2 CLEAN OUT POINTS. Its important to flush the drain every few years

Replaced sump with twin pump system and battery backup with alarm

Tied stairwell drains to drain / sump system

Installed dimpled membrane on wall that will divert any wall seepage to drain/sump system

Dug out / cleaned window wells 3ft down and re-graveled

Added proper exterior grading, swale system downspouts and french drains

[Joey Wharton]

I should add we found a water source under the property. Its key to locate the source of the water. If its all surface run off an exterior plan may do it. If there's hydrostatic pressure, then you either need an exterior perimeter drain where they dig out to the base of the foundation on the outside, or an interior drain, such as I put in. No matter the case, you need to mitigate exterior surface water run off in conduction with a perimeter drain.

[Steve Babiak]

Originally posted by @Joey Wharton:

...

Tied stairwell drains to drain / sump system

...

Dug out / cleaned window wells 3ft down and re-graveled

...

In the future, you should consider treating the window wells as you do on the stairwells - they are a point where water will collect, so tieing those in to the sump should be considered. 

[Joey Wharton]

Agree however its not advisable to bring exterior water in so we are tying window wells to an interceptor drain.

[Stephen S.]

I just installed two 24" diameter by 6' deep sump-pump pits.  I dug through water for almost the whole depth but after I got down to about 5' the clay layer ended and the pits became free draining.  So I'm hoping that now I won't even need pumps. <g>

stephen

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[Ariel Cohen]

As @Joey Wharton mentioned, it is also important to make sure you have a backup pump and power source. In my area, people have lost basements multiple times, and it is usually from a single failed pump or a power outage during a storm without a backup power source. 

[Ryan Thacker]

Great responses so far! The science of water is simple. It will go wherever it can. If this was my problem, as a DIY guy, I would put in an exterior French drain system. If you decide to go this route and hire someone read the link I posted and make sure that this is the way its done and that they put in a clean-out incase it gets clogged ever you can call a plumber instead of digging everything up again. Again I'm no professional just a DIY-er but an exterior French drain system sounds like your best and cheapest option.

Here's the link on the right installation:

http://www.easydigging.com/Drainage/installation_french_drain.html

Here's on why it works:

https://www.youtube.com/watch?v=qgFSMCRhwco

Hope this helps.

[Mindy Jensen]

So much great information. Thank you! My neighbor doesn't feel comfortable with this level of DIY, so she has found a company that will do it and guarantees the work. They are a nationwide company that has been in business for a long time (I can't remember if it's 40 or 75 years) and they have invented their own system with sump/backup sumps. She feels she is in good hands with them. I am going to try to be onsite during the installation to check it out and hope to share.

[George P.]

great responses. a system around the whole 1k sq. ft basement here would be around 5-9k. 

[Blake Taelman]

For what's it worth, I've had to rip up the of and install interior drain tile in a home I built before for this exact reason. The water table was just too high. However, it is the most expensive option so make sure that window well drains are clear and that the water isn't a result of exterior rainfall hitting the footer and seeping into the home. Everything should slope away from the home. If all the wetness is around the perimeter of the basement, I don't know that I'd start with an interior system.

[Mindy Jensen]

Well, here we are, the day of the installation of the interior french drain. The guys ripped out the drywall, cut the studs, and started in with the jackhammers - only to discover that they have a (I'm using her terms here) a monochromatic foundation. It has no footers???

The foreman said he has been doing this for 13 years and only seen this once. The salesman said he has been doing this 5 years and only seen it once. 

Structural Engineer is coming out to check, but all work has stopped. She is in tears. The second option is to dig around the entire house, all the way down to below where the foundation starts, because the water is pushing up from under the house, rather than leaking in through a wall.

Any experience with this? Any suggestions?

Thanks, BP Community!

[Steve Babiak]

Originally posted by @Mindy Jensen:

Well, here we are, the day of the installation of the interior french drain. The guys ripped out the drywall, cut the studs, and started in with the jackhammers - only to discover that they have a (I'm using her terms here) a monochromatic foundation. It has no footers???

The foreman said he has been doing this for 13 years and only seen this once. The salesman said he has been doing this 5 years and only seen it once. 

Structural Engineer is coming out to check, but all work has stopped. She is in tears. The second option is to dig around the entire house, all the way down to below where the foundation starts, because the water is pushing up from under the house, rather than leaking in through a wall.

Any experience with this? Any suggestions?

Thanks, BP Community!

It's called a "monolithic pour" or "mono-pour" where floor and foundation were done at the same time with one big batch of concrete. The experts from this company have only seen it once??? And the experts couldn't ascertain that they were going to encounter that on this job??? The jack hammering has to leave enough "meat" behind so they will have to pull in a bit from the walls. Not a structural expert, just what I have seen before. If the walls are block walls, this can be detected by observing the first course of block, to see whether it is a full block or a partial block that is visible above the floor level. 

http://forums.finehomebuilding.com/breaktime/gener...

Hopefully they only cut the studs real close to the ground so repair is just sistering. And the drywall should have been cut close to but a bit less than 4 feet from ground so repair with full sheets is simpler. 

[Mindy Jensen]

@Steve Babiak, Are you looking for a job? I've got this basement with issues...

OF COURSE they didn't cut the drywall 4 feet up. They did, however, cut the studs close to the ground and sistering is how I suggested they repair. The basement guys don't do the repairs...

My friend is not well versed in building terms, and I wasn't there to get the information directly from the basement guys, but they are telling her there are no footers. I looked around the basement and couldn't see how they could tell that from what they dug up, but they dug up a bunch of different places before they figured this all out. Again, I'm not a basement expert.

She is at the end of her rope. Her basement has been flooding for two years, following 3 years of drought-like conditions - we are a desert, after all. 

[Alison Robinson]

Hi @Mindy Jensen,

I suffered through fifteen years of basement floods in my first personal residence. The immediate neighborhood did not have storm drains. Storm drains from the main street were undersized so we would get what looked like river rapids flowing past our house during major storms. We had a sump pump so normal or average rains would result in small amounts of water leaking into the basement. The walls were block construction build in 1950s-60s. During really heavy rains everything would backup and we would have bulk entry of water. The absolute worst situation was when there was a power outage during a heavy rain. We did not have a battery backup on the sump so the basement would completely flood. This happened about a half-dozen times over the 15-year period. Eight years ago we paid Everdry Waterproofing to fix the problem. They installed interior drains along the basement perimeter, added 2’ deep drain pipes along 50% of the exterior, lowered the sump pump and added a battery backup. Finally a dehumidification fan was installed. It cost us better than $10K to have it done. We pay $50 a year to maintain a lifetime warranty on the work. I feel like I overpaid but eight years and counting no water.