Answer: 68 inches Explanation: We've always done 6 to 8 just for foundation purposes 
SouthPac Construction 
Answer: 46 inches Explanation: Standard concrete floor slab thickness in residential construction is 4 inches. Five to six inches is recommended if the concrete will receive occasional heavy loads, such as motor homes or garbage trucks. 
Colorado Concrete 
Answer: 46 inches Explanation: Normal slab for residential structure would be 4". There are grade support beams through the slab also. 
Design4 

ProMatcher 
Answer: 46 inches Explanation: Our average thickness is 4in and we use #3 rebar on 16in centers with 3000 psi concrete. 
A to Z Fence and Concrete 
Answer: 46 inches Explanation: 4 inches except for perimeter which should be a 8 inch minimum 
DIRTCO CONSTRUCTION 
Answer: 46 inches Explanation: Residential concrete slabs should always be poured at 4 to 5 inches with compacted fill and footers at blueprint spec,to avoid any sinkholes in the future. 
Lals Concrete Company,LLC 

ProMatcher 
Answer: 46 inches Explanation: This really varys it all depends on how the house foundation is built and also where it is built. I have done homes in Georgia that where post tensioned and the footing only where 12 inches. Then I have done homes in Michigan and footing where min 27 inches. It depends on the specs and the climate you live in 
h and h company 
Answer: 24 inches Explanation: Residential concrete slabs are typically 4" 
Concrete & Beauty Design 
Answer: 46 inches Explanation: Sometimes 8 inches and with wire mash 
Garcias Concrete Service 