Expert: Ted Barnhill (Principal, Design45 LLC) - 2/24/2009

Question
Hi Ted- I converted an attached garage to a room.  City says I need to have a vapor barrier below the concrete to be permitted.

I live in sunny So. California; is there any other way to satisfy the city other than digging up the concrete, laying down a vapor barrier and re pouring the concrete?

Can't I roll some polymer type coating on top the existing concrete and below the pad / carpet?

Thanks so much!!!

Dan

Answer
Dan,

I do agree that there should be other ways to minimize the movement of moisture and soil gasses into your room.  Tearing up the slab is quite a project to address that detail!

There are many coatings tested to act as vapor retarders, but you'll have to find documentation to show that your proposed floor paint satisfies the perm rating that your city is looking for.

Another possibility is to put a poly vapor barrier on top of your slab, seal it at the perimeter, and lay a floating floor on top of that.  This can be a finished product, or an unfinished interlocking subfloor that you could then carpet over.

However, dealing with code officials is a sensitive business.  I suggest that you approach them with respect, ask for their opinions, and try to work out a solution that they will approve.  Good luck, Ted