crawl space and basement, soon to be filled in
farmgirl6
| Posted in General Questions on
Hi, I’m going to tear down an old house and build in the same spot. The old house has a 2ft dirt crawl space and a 10x10ft basement. The new house will have a concrete slab, 40ft by 32ft. I’m wondering if anyone has ideas for using the basement and crawl space in designing this new building. I’m planning to ask the engineer about using the crawl space for horizontal geoexchange. And I am thinking about trying to locate a rainwater cistern in the basement. I just want to consider the possibilities before the hole is filled in. Anyone have any experience with this situation?
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Replies
Your problem is your new slab needs a very solid base. If over time the ground under the slab settles the slab will crack and shift. What left of the now tilts to the left and other side of the crack tilts the other way by 1 or 2 degrees the gap at the slab is tiny but 20 feet up the gap wants to be 2 inches. This will try to tear the house apart.
Getting the fill properly compacted is difficult enough without worrying about not crushing a heat exchanger.
Ask the engineer how many times the contractor needs stop filling the basement and compact before adding more fill my guess is about every 8 inches.
In an ideal world the slab would be on undisturbed soil when that is not possible clean crushed rock fill is the next best option as it tends to lock its self in place.
I say if you want a hole dig a new one someplace that will not be under the slab or if can drain it to daylight a full basement.
Walta
I'd see if it would be possible to use the existing basement as a mechanical space. You'd need a way to get down there, so a stairwell would have to tie into your existing design. Then it would just be a matter of framing a floor over it (assuming the foundation walls are in good shape), and getting that up to the level of the slab that would be the floor for the rest of the house.
Bill
More than anything, I’d just be sure to have a solid capillary break and a hefty layer of sub slab insulation!
There is the occasional older homes around me that is built partially slab on grade with a small basement. The basement in these is usually used for equipment, great spot for you DHWT and HVAC.
I would keep the crawl and basement and use them similar way. There is no point in filling it in unless you have ground water issues. Make sure insulate and take care of drainage.
Geo loops need area, partial area under a house is nowhere near enough. I might be just enough for a pre-heater for an HRV/ERV but even there is hard to get any ROI on energy savings.