SLAB ON GRADE

Dirthog · Mar 16, 2007

You cannot pour the footers and floor all in one for that type of building at least the ones I have worked on you pour the floor after the building is up to fasten it to the footers.

RichNJKubota · Mar 16, 2007

We used a "haunched" (spelling?) slab (12' x 26') for our breezeway between the house and garage. The footings are 4ft deep by 1ft wide and filled with 3/4" clean stone. The edge of the slab is 1ft thick concrete while the center is 6" thick. No rebar.
So far, after 10 years, there are no cracks.
PT 6x6 posts sit on the outer edge of the slab to support the breezeway roof above.

flINTLOCK · Mar 16, 2007

Can I place 12" footers @ grade on 6" stone and use 10 inches of stone under 6" slab to make up the difference. I prefer monolithic pour to minimize time and get tractor locked up under roof ASAP.

dirtworksequip · Mar 18, 2007

Check with some area cement contractors and see what they say about setting it up that way.

jimmysisson · Mar 18, 2007

flINTLOCK said:
Can I place 12" footers @ grade on 6" stone and use 10 inches of stone under 6" slab to make up the difference. I prefer monolithic pour to minimize time and get tractor locked up under roof ASAP.

I'd say if you have good draining soil this haunched design will work. If you have clay or wet soil the frost will go right through the slab and footers and might heave the building. It's always a shock how easy frost lifts something big and heavy.
Everything hinges on how well drained the site is. That and what the building inspector/code has to say about it. For common sense though, if the frost can't get under the footer, you're ok. Some 1" EPS foam will keep frost from going through the slab, and keep down the sweating in summertime too.
Jim

RichNJKubota · Mar 18, 2007

The area the hauched slab is located is very well drained. No chance of any water getting under the slab. I also put 4" of rigid foam insulation between the crushed stone and slab. And just in case the breezeway ever gets closed in for living space I put PEX tubing in the slab.

jimmysisson · Mar 19, 2007

Sounds like you did the work already? No input from the building officials?
If not, the haunched slab will work just fine.
Jim

flINTLOCK · Mar 20, 2007

Yea, I'm going to end up with a foundation you could build the empire state building on till I'm done. Need to go at least 42" deep for frost, 12" wide with 6" slab. Who knew.

jimmysisson · Mar 20, 2007

flINTLOCK said:
Yea, I'm going to end up with a foundation you could build the empire state building on till I'm done. Need to go at least 42" deep for frost, 12" wide with 6" slab. Who knew.

Well, it's nice not to have to think about it any more. Until you want to change it!
Good luck,
Jim

RPK · Mar 21, 2007

CT uses the 2003 International Building Code for out buildings on residential properties. Table R404.3 shows design requirements for a monolithic type slab on grade with (2") foam board insulation around the outside perimiter of the slab. A piece of foam goes verticle against the concretel and a piece lays flat against the verticle piece around the perimiter of the slab. Sort of L-shaped. The crushed stone is to help provide good drainage under the slab. The foam board is an alternative to a full frost-protected footing and concrete wall 42" deep (CT frost depth). This is common design for smaller buildings such as yours. Find out from your Building Inspector what version of the code your town uses and do a little re search to see if this may be acceptable for your area.
RPK