I am building a cement pad. In the future it will be a floor for a garage. I am including a 1 foot wide and deep perimeter. The inner space will be 6 inches deep. I am not sure on the rebar spacing. Any help is appreciated.
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Concrete Slab Foundation
I gather from your description "concrete pad" you are talking about a monlithic concrete slab type foundation.
The thickness and strength of the concrete, and the size and spacing of the rebar will be determined by the soil the it will be sitting on and the load /.weight of the structure that it will be supporting.
The IRC (Internation Residential Code) sets out some minimums for slab foundations for various soils etc.
Since you did not fill out your profile, I don't have a clue as to where your located. Geographical location can be a major factor in the design. Are your soils sandy, gravely, silty or clay.? What is you frost line?
Are you located where a building permit is required? If so, they will take all of the guess work out of it and tell you what you will be required ot do.
The foundation you are proposing is fairly large. First impressions is that the perimeter beam / footing is too small and the interior slab is unneccessarily thick. Size and spacing of repar, I would not care to speculate.
Look at similar foundations in your area? Talk to a concrete contractor? Talk to an engineer. What you are wanting to do is not all that simple. Good Luck.
Standard construction.
Standard construction would call for the footing to be 12" deep X 12" wide. (The depth of the footing is measured from grade, not the top of the slab.) With # 4 (1/2") rebars at the top and bottom of the footing. A 6" slab is excessive; 4" nominal is required.
Slab reinforcing is often not required. All this assumes decent soil conditions. Non expansive, no fill, 1000 psf soil bearing capacity.
Hire a pro
There's more to concrete work than just pouring mud. Often, the details are deal-breakers.
Example: In northern Nevada, there are many examples of flawed concrete pours- primarily because the contractor did not know how, or care to, properly deal with the effects of high altitude, high heat, and strong sun on the pour. As a result, the surface was tooled far too long, the concrete lost moisture before it cured- and the result is considerable spalling.
Probably the most often overlooked detail is to make sure the slab has good drainage under it. This means both a good bed of gravel- as well as a place for the water to go. Depending on your site, it may be advisable to divert ground water around the slab
Related to this is the integrity of the soil under the slab. It should be 'undisturbed' as much as possible. Since it may be fill, you might even want to compact it. The idea is to minimize movement in the soil as time goes by. Soil movement = cracks. Likewise, tree roots will break the slab in a few years, if the trees are too close. Folks seem to forget that trees grow..
Folks often attach wood framing directly to slabs. This can be a serious error, as it places wood too close to the ground. Wood near the ground will rot, and may attract termites, ants, and other vermin. Far better to incorporate a 6" "curb" atop the perimeter of the pour.
Finally, how will you finish the surface? A contractor will have a machine he can ride about on the slab. He'll have practice in making the surface just rough enough - and in giving it just a wee bit of slope - especially at the entrance - to prevent water from pooling inside the garage. The contractor will know when & where to add expansion joints and stress grooves.
A Florida mono slab will have a 12x12 perimeter with 2 #5s in it. You can use 6x6 #6 wire but I usually tie in #3s at 3-4' intervals just to hold the wire flat and get better support from the chairs.
You do want a well compacted base and gravel if local conditions warrant it.
If you are ever thinking about electricity out there, attach a #4 copper wire to the footer rebar and bring it up in a place where it will survive the building process, near where your electrical panel will go. That is your best grounding electrode and may even be required by your code. Some places will just let you bring up a piece of rebar in an accessible place that you can attach to later but this is usually where block construction will be used.
Also think about J bolts on the perimeter to anchor the walls if this is stick framing.
Again Florida will have additional requirements for uplift.