Footing drain
Poliana
| Posted in General Questions on
Hello again,
I want to ask you guys about the purpose of the footing drain. Is the footing drain installed for surface water or ground water? The guy who installed the footing drain says is just for surface water only. He also is saying that the footing drain has to be dry. Could you please clarify it?
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Replies
Poliana,
It's a hard distinction to make. Surface water should be directed away from the foundation, but when it percolates into the soil, it becomes ground water. What the contractor may mean is that if there is a high water table, and ground water is coming up inside your foundation, the perimeter drains may not solve that.
The area around the footing drain should be dry in that if it is working, the surrounding water will enter it and be directed away. But to do that the drain itself is of course wet.
Edit: I see from your other post what the contractor meant. The two solutions i'd suggest are:
- Install a sump with sufficient drain-rock under the slab to relieve the the hydraulic pressure and direct the water to the sump pit.
- Install several runs of perforated drain pipe inside the foundation surrounded by drain-rock, and tie these to your functioning perimeter drain system.
I thought it's not recommended to install sumpump in New homes.
The Footing drain is usually down around the bottom of the footing and drains off ground water to relieve pressure that would otherwise try to drive the water into or through the wall.
Surface water drains would drain water from the surface. Your contractor may mean that a footing drain is not intended to act as water well does supplying constant water.
Bill
Bill brings up the location of the footing drains, which is important. Do you know that they were installed next to the concrete footing, where they should be. An all-to-common mistake is installing them too high which may not help keeping water from penetrating the joint between the footing and foundation wall. Here an article that may be helpful:
https://www.greenbuildingadvisor.com/article/how-to-install-a-foundation-drain
+1 on this. If so, it's likely that patching with hydraulic cement will not work. A sump pump might. I'm not aware of any method to check drain depth at this point (well, other than digging).
You could raise the crawlspace floor with gravel (until above footing drains) and cover with plastic or plastic+concrete.
Is it ok to dig and check the footing drain of a new construction?
Yes, just be careful you don’t damage anything. The typical corrugated drain pipe isn’t very strong, you can damage it with a backhoe easily, and even aggressive hand digging can slice the stuff.
There is a device used in the utility industry known as a “sonde” that can give you the depth of a buried pipe IF you can slide it in. The better underground utility line locators can also do this if you can get a piece of metal or a wire poked into the drain line. Look up “utility locator” for your area, USIC is one such company that does this nationally, but normally they work for utility companies. I don’t know if they’ll do a one-off residential job but it might be worth calling them if you are worried about digging.
I will do my utility industry duty and remind you to call 811 before digging to get things like gas and electrical lines marked.
Bill
Hi Poliana,
I've been following the situation you are having to deal with because my house is similarly on a hill and has drainage problems in the crawl space. One thing I'm confused about is that your home is variously described as having a crawlspace and/or a basement. I'm not sure I'm understanding this as usually a home has one or the other. Generally a home that is located on a hill requires a sacrificial area usually described as a dirt crawlspace and post and beam supporting structure for the house. This is even in areas of the country that usually have basements. This sensible type of construction allows for water management where there is hydraulic water pressure from gravity of water flowing against the high side perimeter foundation. This is pretty much a physical problem that can't be avoided for construction on a hill so it's best to not cover it up with a cement slab. Ideally one would level the ground around the house so there is a swale that divides the flow of water to both sides of the house on the high side. It's just difficult to keep water out of the crawl space on a hill because of that gravity fed hydraulic water pressure. Dirt floor crawl spaces are a sacrificial measure for the worst case scenarios where that water can come up from below from that water pressure.
If I'm understanding the way your house is built then you have some form of slab. In that case maybe the best solution is to go the full monty while the perimeter drains are dug up. In other words, dig down to the bottom of the foundation wall ON THE OUTSIDE and put up a water barrier and dimple mat against that wall. Again, it has to be on the outside of the foundation. Put in a new perimeter drain that you are assured will work. If you go this route the new drain is not an expensive addition to the undeniable expensive perimeter foundation sealing work on to the outside foundation.
Finally, go out about 20 feet or so from the house and lay non water permeable poly that drains to the perimeter drains. This will keep water from collecting below the surface of the ground beneath your slab but will instead drain it before pressure is allowed to build. It's very sad that your architect/builder didn't know that and that you are the victim of his ignorance.
In my case I've been able to just seal interior poly to the walls and floor of my dirt crawlspace and it eliminates the excess humidity that would otherwise contribute to cupping wood floors and rotting wood below the house. I left a 1 foot section on the low side of the crawlspace uncovered for the water to evaporate during the dry season. That doesn't seem to be a solution available to you. I'm holding good thoughts for you and your husband and hope the universe treats you kindly on this problem you don't deserve.
Thank you Eric. I read your message 4 or 5 times to understand what you are saying. Are you an engineer or an architect? I have a crawlspace, but sometimes I just called it basement as I don't have the word " crawlspace" in my language. Thank you so much for your advice and positive thoughts. It's been very challenging for us as we have more problems than the water in the crawlspace. Here are a few: copping floors all around the house. The architect bought a dehumidifier for the crawlspace which I really didn't want that when I bought the house. He wants to seal the gap between the slab and the wall with hidraulic cement which doesn't make any sense for me. It's a struggle for us.