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-   -   shouldn't I have gravel under concrete footers? (http://www.diychatroom.com/f105/shouldnt-i-have-gravel-under-concrete-footers-158306/)

wspev 09-28-2012 07:00 PM

shouldn't I have gravel under concrete footers?
 
I live in the state of Georgia and I am having a couple of second story decks built. Our contractor is telling me that a layer of gravel is not needed under the concrete footers. I called the inspections office in my area and spoke to the lead inspector in my area and he told me the same thing, but couldn't tell me why gravel isn't needed under the poured concrete. I called the inspector for a second opinion. But everything I read says you should have gravel under concrete footers for drainage purposes of water. I am wondering if I should just ask the contractor to put some gravel in anyway before the concrete gets poured into the holes in the ground for footers.

Opinions out there?

GBrackins 09-28-2012 07:20 PM

Welcome to the forum!

footing should bear upon undisturbed virgin soil. the only time gravel/stone comes into play is when the excavation has been done too deep and instead of placing more concrete you decide to use structural back fill (which by code is to be designed by a professional engineer).

here is the code section from the 2009 International Residential Code, the basis of most local and state building codes:

SECTION R403 FOOTINGS

R403.1 General.
All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other
approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.

hope this helps! :thumbsup:

wspev 09-28-2012 07:38 PM

Thanks Gary for the code. :thumbsup: Not sure why the inspector couldn't tell me this. I guess I am used to they way I saw footers being done in New York State. Gravel was always used under every concrete job (footers, slabs, driveways, etc.).

I see from the code that you sent me that gravel isn't required and that the concrete should be on Virgin soil, but where the heck does that rain water in the earth (and around and under the concrete) go when it rains I wonder? hmmm.

bbo 09-28-2012 07:48 PM

it percolates at the same rate as the soil. it would be the same under the footing as the surrounding soil, right?

Bondo 09-29-2012 11:28 AM

Quote:

Originally Posted by wspev (Post 1019519)
Thanks Gary for the code. :thumbsup: Not sure why the inspector couldn't tell me this. I guess I am used to they way I saw footers being done in New York State. Gravel was always used under every concrete job (footers, slabs, driveways, etc.).

I see from the code that you sent me that gravel isn't required and that the concrete should be on Virgin soil, but where the heck does that rain water in the earth (and around and under the concrete) go when it rains I wonder? hmmm.

Ayuh,.... It goes to the same place, in the same way it did, Before ya put in the footers...


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