Expert: Michael Curry - 10/21/2007

Question
QUESTION: Michael,

I'm trying to add a walk in closet to my master bedroom on a preexisting slab
under a shed roof.  the slab is at the same level as the interior floor.  I'm
looking for some advice on how to insulate the floor (I'm assuming I need to
since I live in a cold climate) without jackhammering the slab and how to tie it
in to the rest of the house.  Thanks

ANSWER: Hi Andy,
You can't tie into a slab in a cold climate unless the slab is part of a slab your house is on. The frost will move the slab every year and separate the addition. An alternative is to remove the slab and pour a foundation below the frost line (4' is usually good) or build on piers that are buried below the frost line.

Thanks,
Michael

---------- FOLLOW-UP ----------

QUESTION: the slab is at least 5 years old, perhaps 10 and the house is 70 years old.  
there's no noticeable movement or settling of the slab.  the posts and framing
on the porch roof are way overbuilt. would I be crazy to go for it (building on
the pre-existing) anyway?

Answer
Hi Andy,

The problem is that the house has a foundation below the frost line and does not move. The slab almost certainly moves with the frost and goes un-noticed. Once you build walls and attach the to the house they will get pushed up every winter. Theres no way you will even get a permit to do this. I would remove the slab and pour some piers, as a cost effective remedy.

Thanks,
Michael