Home Foundation Turndown Slab Drainage System
TronPlayer
| Posted in General Questions on
How many of you have installed a below grade “french drain” system for your slab foundation? The footer is 12″ below the frost line. It gets fairly rainy here in the summer but all three different concrete companies I’ve taken bids from say you don’t need any below grade drainage system. The pad is graded for drainage and rain gutters will be installed. I’d rather not put it in but I’m tossing and turning about it. 🙂
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Replies
Tronplayer,
You will be fine. If the site is wet enough you think it needs addressing, rather than perimeter drains, deal with the areas with standing water with grading or trench drains.
Make sure to include a layer of free draining washed rock under the slab to stop any ground water from moving upwards by capillary action.
Or as Martin much more succinctly put it:
"Below-grade foundations require perimeter drains, but above-grade slabs do not. That said, site drainage -- meaning good grading -- is always important. The grade should slope away from a slab in all four directions."
You may find this article useful: https://www.greenbuildingadvisor.com/article/different-types-of-insulated-slabs