French drain next to foundation?
French drain next to foundation?
(OP)
as a chemical eng, the only thing i know about soil is not to spill any toxic chemicals on it. i was hoping for some cross discipline help on my latest project.
I am putting in a gravity french drain around my house to dry out my crawl space (6"-1' of standing water during big rains). they are very popular in my neighborhood due to heavy water runoff from the surrounding hills. my house has a perimeter foundation (likely with a t-footing) with about 2-3' above the ground (believe 2-3' below grade also) and has concrete piers inside.
some drainge contractors locate their trenches 2-3' on outside of foundation and 12" below, while others put it right against the foundation. if you put it next to foundation, wouldn't you undermine the structural intergrity? especially if you dig 12" below it-are there not some type of lateral forces on the soil that could cause foundation shifts since you back fill with 3/4" rock? my pad and back yard are flat with about a 3' slope from front door to curb.
thanks
steven
I am putting in a gravity french drain around my house to dry out my crawl space (6"-1' of standing water during big rains). they are very popular in my neighborhood due to heavy water runoff from the surrounding hills. my house has a perimeter foundation (likely with a t-footing) with about 2-3' above the ground (believe 2-3' below grade also) and has concrete piers inside.
some drainge contractors locate their trenches 2-3' on outside of foundation and 12" below, while others put it right against the foundation. if you put it next to foundation, wouldn't you undermine the structural intergrity? especially if you dig 12" below it-are there not some type of lateral forces on the soil that could cause foundation shifts since you back fill with 3/4" rock? my pad and back yard are flat with about a 3' slope from front door to curb.
thanks
steven





RE: French drain next to foundation?
RE: French drain next to foundation?
RE: French drain next to foundation?
Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve
RE: French drain next to foundation?
thanks all,
westcoastr
RE: French drain next to foundation?
RE: French drain next to foundation?
If it's surface runoff (from nearby highpoints), the you really only need to follow lha's advice above (simple perimeter drain just below surface, smack adjacent to your crawl space wall). You would really only need to do this on the sides of the house that are in the path of the surface runoff.
If it's a high water table, then I probably would go with a full perimeter drain. As others have stated, don't undermine your footing by putting the drain below the very bottom of it - that's overkill anyway as you just want the water to stop ponding whereas you really don't need to drain every bit of water from 0" to 36" below the surface.
The trench you dig can be put right adjacent to the foundation wall and then sit and rest atop the footing (the T as you call it). Again follow lha's advice on how to construct. This will keep you dry and safe.
Aside from putting in a drain, does the ground surrounding your house pitch down, so that rainwater runs AWAY from your house, and NOT towards it? Are your downspouts properly disbursing water AWAY from the house? Consider these simple-fix items too!
Do overthink this one! & good luck!
RE: French drain next to foundation?