Contraction Cracks
Cement concrete expands and contracts by changes of temperature in the same way as steel. It is, therefore, necessary to cut joints which will allow for this expansion and contraction. The concrete must be cut entirely through to the bottom of the slab with a trowel, cleaver or other instrument, the joint formed being from ⅛ to ¼ of an inch wide. Blocks formed in this way should not be greater than 6 feet square (36 square feet).