Residential Slab

[jrtm76]

I am a residential designer and have a renovation proyect of an existing home with a single story 20'X20' addition. The foundation will be a monolithic slab with turned down perimeter footings. What are the reinforcement requirements/guidelines for this type of slab? This is in North Atlanta where the frost depth is 12".
The county has no specific requirements or guidelines but does require an inspection. The concrete contractor won't pour until we have drawings showing rebar and steel reinf. Homeowner cannot afford engineered drawings(it is such a small proyect). I have searched my residential code books and have not found anything that would point me to the right direction.

All help will be appreciated.

 

[PSlem]

It's in the foundation section. One #4 top and bottom in the footing. They only require gravel for basement slabs but slab on grade or basement require the poly.

 

[boo1]

we need more information, what is the soil condition?
Red Georgia clay?
Is there a brick veneer?
One story or two?
Grade beams?

Typically with non-expansive soils use 2-3 #4 grade 40 at bottom with 2 inch cover, 3000 psi mix, 6-mil polly, 10x10 wire or fiber additive. I would dowel the slabs by drilling and epoxy a 12 inch #4 (six inches) in the existing slab @ 4' OC to prevent movement between slabs.

 

[boffintech]

If the turn down edge of the slab is cast using earth as the form the cover requirement is 3”. If wood or metal is used as the form and then the area is backfilled, the cover requirement is less.

ACI-318
7.7 — Concrete protection for reinforcement
7.7.1 — Cast-in-place concrete (nonprestressed)
The following minimum concrete cover shall be provided for reinforcement, but shall not be less than required by 7.7.5 and 7.7.7:
Minimum cover, in.
(a) Concrete cast against and permanently exposed to earth = 3
(b) Concrete exposed to earth or weather:
No. 6 through No. 18 bars = 2
No. 5 bar, W31 or D31 wire, and smaller = 1-1/2

 

[jrtm76]

Thank you for the responses.
There will have to be a masonry legdge for brick and or stacked stone. There is a portion of the addition that will be supporting a second floor.

Jr

 

[boo1]

Consider using three #5 (one in the brick ledge) 20 inch wide x 20 inch deep (6 inch in the brick ledge).

Can someone else recommend the dowel pattern?

You did not indicate the soil condition.

 

[Ron]

jrtm76....I knew Georgia was a bit lax in their engineering requirements, but I'm surprised that you can get a permit for a 2-story structure without some engineering input and signed/sealed plans.

 

[kxa]

I think all the reinforcement bars are now grade 60. I would use #4 rebars as dowels and space them no more than 18" oc for the slab. Dowels between the new premeter footing and existing would have to be based on the load it would have to support.

 

[boo1]

All the residential foundation contractors in my area (Northern Florida) use gr 40. I never design residential for 60 since I know I would have to fight to get them installed. It's hard enough to get them to use 10" long anchor bolts. lol

I would not use/design dowels to support loads, for residential additions we use them too prevent uneven settlement