Expert: Bruce E. Johnson - 4/7/2009

Question
Hi, Bruce. I am preparing to enclose my carport into a bedroom and just started trying at getting the permits.  It's a concrete slab with a roof overhang.  The inspector we (my wife) talked with mentioned that we'll need a frost wall.   I haven't heard this term before.  Is he talking about pouring a footing below the frost line around the carport slab?  He said it's to prevent moisture "sweating" of the pad.  I have seen this sweating before but how will a footing prevent this?   
Also, is it best to break away the edges of our slab to pour a footing directly under the roof line, or can we dig it at the edges and form it in over our pad to support the wall?   
Thanks for any and all help.

Adam

Answer
Hi Adam, The purpose of a frost wall is to contain an area of dirt that will be heated and stay contained during heavy freezing.  And yes this will cut the condensation down.  So, I guess you could do the wall outside the slab to achieve this.  I think you need to go down to the building department and get them to clarify exactly what they want you to do.  Apparently this is a common thing in your area and there are probably several accepted practices to address your particular needs.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com