Sub-slab drainage stone size
JTyler
| Posted in GBA Pro Help on
I know the typical recommendation is 3/4″ no fines. Foundation contractor and stone supplier are recommending I use 1.5″. Foundation contractor is trusted and has used product a great deal including under some very dry basements that I’ve been in. Stone guy says he has 3/4 no fines – but it’s more money for no gain. I have seen the product they are calling for; it’s a mix of ragged and round stone that would surely drain very well. I can tractor stone in, so will be able to minimize trying to stick a shovel in it. SDR 35 interior footing drains. Any reason not to follow their recommendation?
Thanks!
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Replies
Jim,
The main reason I prefer 3/4" stone is that it can be moved with a shovel or rake. If you are very good at leveling stone with your tractor, bless you. Not everyone is that good with a tractor.
I always end up filling low spots and raking high spots by hand.
Jim,
Has your contractor used it under foam? I can see it working well directly under a slab, but levelling 1 1/2" fill so that foam lays without voids underneath sound like a difficult job. 3/4" clear crushed interlocks into an almost flat surface. larger rock, especially if it includes round stones, might make this difficult.
Thanks for the input guys.
It would be incredibly tedious to try to level 1-1/2" with a small machine or by hand. You could get it flat using a road roller, but that seems unlikely for a residential slab. We use 7/8" clean and it can be done fairly easily by hand raking and a plate compactor.