Expert: Stephen Major (Owner--Major Design Group) - 8/1/2007

Question
My home has a mono slab and I am adding an addition to my house. Join one slab to another slab both are Mono slab.
Someone, said! that to join the new slab to the old I have to drill 6" holes into the side of old slab and put #4 rebars 1'long in to the holes then pour concrete so the slabs won't seperate.
Is  this Rihht?


Answer
Doug,

It is common practice to join the slabs so their surfaces remain flush at the joint.  The correct way is to use smooth rebar (not deformed), and grease the protruding ends prior to pouring, so the new slab can pull away slightly during curing (to minimize cracking).  

It's important that the subgrade be well compacted so that little or no settling occurs after concrete placement.

Best of luck and let me know if you have additional questions.

--Steve Major