How to Overlap Rebar? 

Rebar is manufactured in 20-ft. lengths.  When rebar must be spliced to make it continuous or joined at corners, the length of the lap should equal 30 bar diameter, as shown below.  Always refer to your structural drawings and details, as of the splicing may change depending the strength of the wall and the use for such.

How to calculate the overlap 

The structural drawings will usually show the desire splice for the rebar, depending on each size.  For example, a typical detail will show 60 bar diameter splice for all footing bars. 

This  formula can be resolved as follows:

Thickness of rebar = ½” = Bar Diameter.

½ x 60 = 30    

The bars will tie together 30”

How many ties do you need for the splice?

Try to tie your splices evenly depending on the length of you splice.  for example, For a 30 bar diameter splice use 4 ties to make sure your rebar is secure.