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).