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Old 08-20-2009, 02:52 AM   #1
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gravel under slab?


We are building a 22x19 addition crawl space foundation and like to know if gravel necessary under the concrete slab besides vapor barrier?
Thanks.

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Old 08-20-2009, 06:50 AM   #2
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gravel under slab?


Yes!! It allows drainage somewhere to flow, it allows some movement from weather changes, etc. And there should a a perimeter drainage system as part of the design.

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Old 08-20-2009, 08:44 AM   #3
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gravel under slab?


Generally, 4 inches of #1 washed stone (#57 or the like) is required by code to aid in under-slab drainage.
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Old 08-20-2009, 09:15 AM   #4
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gravel under slab?


if its mine, crush'd stone,,, according to specs over/down here in sc/ga, compact'd sand-clay - UNLESS a soils test sez different i'd still use vapor barrier over a sand cap, too !
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