Expert: Stephen Major (Owner--Major Design Group) - 4/26/2007

Question
We just finished an addition about a year ago and are ready to install the concrete driveway. We had 3 estimates, and 2 out of the 3 wanted to "Pin" the slab to our foundation. The third contractor made it clear it wasn't the way to do it. What is right? Note we are in the Northeast where the frost does it's damage..  

Answer
Daren,

I pulled you question from the "Question Pool".

I would not pin the driveway.  If the backfill against the foundation is not well-compacted, it will settle and a void will develop.  The concrete will crack and tilt whether you pin it or not.

It is best to be sure that the ground is firm and that any settling has already taken place.  Typically a year or more with rain and traffic is adequate to accomlish this.  Your contractor can power tamp the (well-wetted) area down to an effective depth of about 36" as a precaution.

Lastly, if you do pin it, it must be pinned with smooth bars that are greased just prior to pouring, so the slab can pull away slightly, unhindered, during curing.

Let me know if you have additional questions.

--Steve Major