WATER DRAINAGE PROBLEMS-- FRENCH DRAINS? 1

[kookiemonster]

I am needed a little advise on what to do with a water drainage problem in my house. I bought the home from the heirs of the original owner so there was little to no information on any problems with the home. Shortly after I moved in I noticed that everytime we get a good rain, I get about 100 gallons of water in my garage (I know this because I have a wet/dry shop vac and fill it up several times after each hard rain). After closer inspection of the perimater of the north side of the house, I noticed that this problem has been happening for at least a little while. Either my foundation has sunk or the previous owner has built up the ground to high. The ground around the house is higher than the foundation line and half way up the second layer of brick covering all weep holes. The level of the yard on the back of the house is relatively flat. The level of the yard around the adjacent corner is built up a bit toward the house probably to help channel water away from that side. But I need to a least take down the yard a bit to expose the bricks and weep holes, and probably a little foundation. If I remove ground (about 8 to 10 inches) to allow the foundation to be exposed then I will create a fairly noticable slope toward the house bringing in more water. My question is what system can I put around the perimater of the house to flow the water away after I take down the yard? Also, I should note that my neighborhood is built on possibly the worst possible soil for foundations. I think they call it black gumbo. During dry seasons, everyone actually waters their foundation with soaker hoses to regulate swelling of the soil and prevent cracking of the foundation. I want to be able to prevent rain waters from comming in, while maintaining a balance of moisture in the soil for my foundation. P.S. My bad soiled neighbor is located in San Antonio, TX.

 

[boo1]

So I assume you want a do-it-yourselfer solution and dont want to hire an engineering firm for a formal design. The following drain design should work for you.

Just keep the basic principles clear: The best solution is to grade the peremeter soil away from house for at least 10 ft and have a trench to catch and divert water around the house. Ideally, it could be a wide open trench, but that's usually not practical, so you want to fill it with material that will still let the water move through it and that will keep crud from plugging it up.

We dig the trench at least 36 inches wide and 16 inches deep. The slope of the pipe is crucial to the success of your French drain. So the grade is very important. The trench should slope at least 1/8 to 1/4 inch-per-foot towards its outlet. Lay geotextile, a permeable non-degrading fabric leaving enough to overlap 12 to 18 inches at the top. Spread two inches of gravel or rock (3/4 or 1.5 inch) on the bottom. Locate and install two or three collection boxes as appropriate. Then lay three 6” perforated drainage pipe (function of runoff flow) wrapped with SOCKS in the bottom. If the pipe is perforated on one side install with the holes in the lower side. . Tie the collection boxes into only one of the pipes. Then fill with crushed stone to about 6 inches from the top. I put about 2 inches of pea stone next (small crushed stone). Over lap the geotextile fabric and back fill with coarse mason sand.
The reason I like to use more than one pipe is to separate the collection boxes from the collection line. This adds redundance, and the pipe is cheap. The benefits are that the multiple pipes are much cheaper than the gravel, it significantly reduced the quantity of gravel you will need to shovel into the trench, and it creates lots of annular space in the trench to facilitate drainage.

Additionally consider guttering the run off from the house to the drains.

 

[Jim6758]

I agree with boo1 on the techniques for installing a french drain, but don't agree that multiple pipss are necessary. There is one helluva lot of flow in the gravel itself. A lot of french drains don't have pipes at all, but pipes do improve the performance dramaticly. If your lot is on the high side of the street, you can probably tap through the curb structure. If on the low side, perhaps there is a curb inlet that you can tap into at the flow line for the inlet.

 

[boo1]

Pipe is cheaper than gravel and it works. It also offers system redundancy.

I have used the pipes to run the flow to the curb or a ditch.

 

[kookiemonster]

Thanks guys, I really appreciate your advise. I am not oppose to just hiring out this work. It is just that the companies I had come out a give me an estimate did not convince me that their work would solve my problem. I have taken the liberty to did a trench around the outside wall of the garage. My reason was two fold. I wanted to see how far down my slab has sunk (or how far the dirt was built up) and I wanted to channel water around the house and keep my garage dry. I was very surprised to see an additional layer of brick underground. I dug a 12 X 12 ditch around that side of the house and still only have about 3 inches of slab exposed. Since then, I have spoken with my wife's uncle, who has been in the cement business for 25 years. He said I should definitely have some slab exposed. When he gets into the slower months of business, he will bring the workers and bobcat over to regrade the yard and channel the water away from the house. I quess I just didn't want to tear the yard up, but even installing a french drain 8 - 10 ft. away from the house will require a considerable amount of regrading. Unless, I want to keep the exsisting slope of the yard and put the french drain right up against the slab. For now, I think I will install some of those plastic basins, pipe, and a pop up valve unless of course you think this will not help.

 

[boo1]

Helps yes, solves no. The water must be re-directed away from the slab, look at guttering and down spouts too.

Common construction techinque for modern momoslabs, is to pour a 6"x6" brick ledge extension on the outside peremeter. Typically this is located 11-1/4" below the slab. The thickness may vary but it should be there.