Footer problem or not?
I appear to have a problem with my contractor, because he is not preparing my footer per my plans. I need to know if this is a real issue worth disputing, though I can’t figure out any way to fix it if it is.
I’ve designed a closed, conditioned 3 feet high crawl space in Virginia (climate zone 4A). Most of the stem wall is below ground level.
Moisture control is a major concern of mine. This will be a poured concrete wall, with dimple membrane on the outside and drainage pipe to daylight beside the footer (not on top). The foundation is also surrounded by #57 gravel.
My plans show the footer to be dug so the top of the footer is level with the crawl space floor (which is dirt covered with Stego 15 mil sealed plastic). This keeps the foundation drainage pipe several inches below the floor level.
It appears that the contractor plans to pour the footer at floor level, not below it. (It’s the weekend, so I haven’t been able to ask yet.) The footer trench has not been dug, the backhoe is now gone, and the depth of the existing excavation would require this. The excavation can’t be changed back to my original plan, as the required undisturbed subsoil is now gone.
So, I’d like to know if there are any potential issues with increased water leaking into the crawl space because the drainage pipe is now above floor level (can water seep under the footer)?
I am NOT happy that my contractor appears to be changing my plans without consulting me. But I don’t want to force the issue (if I can even figure out how to fix this), if his changes aren’t going to make a substantial difference. But we ARE going to have a discussion about his not following my plans!
Thanks for any suggestions.
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Replies
Debra, it is a code violation (of the IRC codes, anyway) and poor practice to have the foundation drains above floor level. Doing so can cause or exacerbate moisture problems.
You could add gravel fill to raise the floor of the crawlspace to be above drains.
Debra,
It may be a misunderstanding. We don't trench our footings, but rather excavate the whole building footprint and add sand-fill or gravel inside the foundation to bring the finished surface up above the junction of the footings and foundation by several inches. Maybe that is what your contractor is planning?
The contractor had originally told me that he planned to trench the footings, with a form on one side to leave room for the foundation drain. Every local contractor trenches their footings.
I really wanted the footing and drain to be below the clay soil of the crawl space floor, so the water would have a chance to drain away before it could get high enough to penetrate the foundation.
If we just add sand or gravel to raised the crawl space floor height, the water could still penetrate the foundation, pool beneath the gravel, and raise the vapor pressure differential at the crawl space floor (I think).
But it's good to know that this is an option. I wasn't sure how to straighten this issue out. I'll need to ask the contractor what his plans are, but I wanted to understand all my options before doing so.
Debra,
If that's what you agree to, and that's what is commonly done where you are, then your contractor should trench the footings. That said, there is no mechanism by which water can bypass the perimeter drains, flow under the footings and cause pressure under your crawlspace floor.
It's my experience that where trenched footings are standard practice the foundation drain is routinely placed on top of the footing and where formed footings are used the foundation drain is placed beside the footing. Neither practice is likely to give trouble if the backfill and final grade are correctly installed. If backfill and grade are nor correctly done and storm water is permitted to percolate to the foundation drain then no matter the location of the drain it will eventually will be clogged with silt and then all bets are off. This is why I prefer to think of the foundation drain rather as a vent to prevent the accumulated hydrostatic pressure which no amount of waterproofing can finally resist.
The plastic on the floor will prevent moisture from rising into the crawlspace even if there is water. Gravel fill also adds radon mitigation options (if needed).
Jon is right. If water infiltrates into the crawlspace, it will pond under the liner.