KC wrote:
What is the proper layout to build a concrete patio for a slab house in Georgia with the heat? Does it require 2" inches gravel or no gravel, wire mesh vs rebar and 4" concrete? What is the differences with 3500 psi vs 4000 psi and 5000 psi concrete mix?

Answer:
Great questions, KC! I apologize now for the lengthy response but that's what you get when you ask 6+ questions at once! For a residential concrete patio, you don't really need a gravel base unless you have perpetually wet soils or other moisture problems on your property and need some drainage. If you are enclosing this patio, make sure you treat the underlying soil with an approved termite chemical, lay down a 6-mil plastic vapor barrier before you pour your slab. The perimeter should transition from a 4" slab to a minimum 12" wide x 12" deep "thickened" slab. Per the building code, the footing should extend a minimum of 12" below the exterior soil level… this keeps the bottom below the "frost line" and will prevent the footing from heaving upward in one of our cold snaps. Don't forget to add (2) #4 (1/2" diameter) reinforcing bars along the length of the perimeter footing. The proper type of wire mesh is perfect for your 4" slab. No need to go with rebar. For your purposes, a standard 3,000 psi concrete mix will be fine. Higher strength concrete would be used for surfaces that are subjected to high wear-and-tear such as in a warehouse, etc. It would have to be one heck of a party to wear out your 3,000 psi concrete patio! Beware of the contractor that adds gallons of water to the concrete mix when the truck arrives! Diluting the concrete to make it "easier to work with" or to make it "go farther" will lead to weak concrete that will crack and wear quickly. That's the gist of it! Call us if you need more information.