I need help on finalizing my footing drain design. If this is not the appropriate forum, pls let me know where to ask.
The house will be on a hillside with a walkout basement. Located in Central PA. The land is sloped an avg of 15% or so. Quite a bit of my land is on the uphill side of the house (NW). In a heavy rain (like PA got last year) a lot of water comes down the slope. My planned swale/berm/curtain drain combo will divert runoff around the house. Since I have nothing to base it on, I want to plan on the conservative side to keep water from rising up thru the basement floor. I want to use both interior and exterior drainage. Interior drainage system will double as a radon abatement system (if necessary). The exterior drainage will be directed to daylight further downhill. I would like the interior directed to sump(s) and ejected.
I have attached two drawings in pdf format. One shows the current design for the foundation and drainage. The other shows the planned final grading. As you can see on the foundation plan, we are going to use 8” Form-A-Drain (FAD) on a large portion of the foundation. Not sure how to configure the rest (downhill/walkout), hence my questions. Assume the rest is perf 4” Pipe (PVC/Corrugated).
1. Do I need 1 sump or 2 (as I have shown)? I called for 2 thinking the front half and back half of the foundation would be pretty “compartmentalized” due to the strip footing running the length of the house. Pls there is a lot of floor to manage.
2. How do I configure the interior drain along the walkout wall (foundation wall is all concrete, no framing). With a trench footing the drain would sit on top of the footer at the footer/wall junction. But this would make it too deep to exit into the sump basin. If I raise the drain to the sump height, I leave a large space for water to accumulate. I don’t want to connect the interior and exterior drains (with cross connection thru footers). I believe this would compromise the radon abatement and allow for more potential air infiltration issues.
3. I’m planning on a strip drain inside the garage does (to collect). What would be the best way to outlet that? Right now I’m planning to go thru the side foundation wall of the garage and then connect it to the footing drain. Don’t like this since it would give “critters” a highway directly into my garage. Since this is forested area, there are lots of critters.
Any advice/comments/opinions/thoughts?
Replies
bozo
Sounds like what I went through 25 yrs ago.
We are built into the hill- maybe 8' of fall back to front..........(or front to back)..............
We swaled at the high point at the detached garage (uphill and off to one side of the house) over and around the house location.
Wanted to move uphill water away from the house and that worked. The swale is gradual-can't really see it (we are fairly flat for a hundred ft at the high side of the house), we go upgrade driveway to road. Quite a bit of water runs down the drive-enough to move small stone. This exits down the hill off to the side of the house.
We had thoughts of Radon, and did an interior drain. It's all passive-exits through the low side foundation to daylight. Stands up at the end-caged cap-no vermin. Also drains back to perf. pipe in stone (for the water).
EDIT: I ran perf. pipe below the stone fill, next to the exterior and interior wall footings (we formed the footings both sides-so we easily could lay pipe either side of the footing). The radon-interior drain was all passive-no sump pit or pump. Heavy visqueen laid over top and lapped (for the radon) 2" foam on top of the stone taped also. Then wire, hose strapped to that-concrete and tile for finish. You going radiant in the slab?
No sump inside nor out.
In addition-no gutters. Being in the woods with locust and walnut-I didn't want to battle those small leaves. We ran coating on the block (after parging) , then 2" rigid fibreglass (Warm and Dry at the time), perf. pipe NEXT to the footing and completely backfilled with #57's stone to grade. Exited to daylight down the hill. Hipped roof with a valley uphill side (probably wouldn't do that again-large amount of water comes down there)- but no problem with infiltration.
NW Ohio with damn impenetrable clay. Stuff don't perc here-it evaporates.
Make your swale good and passive and you'll have half the battle won. All you gotta worry about is roof water.
Foundation Drainage
I'm pretty sold on interior footing drains so I need to work out something.
My soil drains. We even passed for a conventional septic system!
Our land is also heavily forested like yours. Not sure what all the trees are. I've seen lots of poplar, oak, sassafrass. I speced out gutter guards (I don't want to constantly clean 167' of gutters!
I plan on using drain pipe to bring the rainwater away from the house.
boz
Check my edit in the post above.
Foundation Drain
No Radiant - Thought about it but, it didn't make the budget
Back to the drain - I'm not seeing how your interior pipe drains then. Where's the outlet if you have no sump?
Using both interior and exterior drain won't cause a problem,
even if not necessary. Like Calvin, I'd suggest diverting as much water as possible by installing a swale/berm and/or french drain up-slope of the house site--say at the 840' elevation. That won't negate the need for footing drains, but this is the kind of issue where a "belt and suspenders" approach is worth while.
I'd try to avoid the use of sump pumpby using gravity drains for both interior and exterior footing drains. The worst case scenario, I guess is a storm that dumps so much water that the exterior drains can't deal with it and then the power goes out and your sump pump quits.
You mention that with a trench drain, "the drain would sit on top of the footing." Actually, the drain pipe should be below the top of the footing to be most effective. You might this helpful http://www.greenbuildingadvisor.com/green-basics/foundation-drains-0
One additional thought about site drainage--be sure that the water from your drainage system doesn't flow over the septic system or drainfield.
Foundation Drainage
I will keep as far from the septic/leach field as possible.
If they are trenching in to pour the footer, in order to get the draintile down at the foot base I will have to excavate after the footer is poured. Or am I missing something?
Still don't understand where the interior drain dumps any water it collects if you don't use a sump or runi thru the foundation/footer?????
Yes- you get to dig
If they are trenching in to pour the footer, in order to get the draintile down at the foot base I will have to excavate after the footer is poured.
Yep. I try to get that digging done as soon as the footings are poured and trying to beat the wall pour - easier to work without being up against the wall. I would bed that tile in peastone (regardless how porous the existing ground seems) and cover with filter fabric.
Terry
boz
Why not excavate for the pipe under footer now-slip a pc of plastic pipe that your drainage pipe will fit through in that hole-form the sides, top w/stone, suspend rebar across that and pour.
Like Calvin, my walkout is in lousy soil, mine being a blue clay.
I tilled inside and out, interconnected through the footing and everything tied to a daylight drain.
I (being a coward) also installed an interior sump just to be on the safe side.
Used a decent 6 mill visqueen under the concrete (unfortunately, no Styrofoam).
I detest floor drains in garages, there always seems to be a bit of a lip around the drain that puddles water, freezes and leaves a slick spot. That or it freezes in the drain basket and won't drain. My preference is to slope the floor 4-5" out towards the overhead doors.
I have the same lower footing detail that you are concerned with. I first thought to run an additional daylight drain at that lower level, but I didn't have enough slope to my grade to make that work. In truth, It hasn't been an issue.
Terry
The reason I want the floor drain is I want to use the heavy duty "lipped" floor gaskets under the garage doors. I have them now and they seal great, too great. I always end up with a lake on the inside of the garage door due to the dam effect of the gasket.
Look into usiung Formadrain for your footings