Expert: Ted Barnhill (Principal, Design45 LLC) - 9/9/2008

Question
A friend would like to build a home extension at the back of her house to extend the kitchen and living area (not sure of dimensions but sounds like a considerable size).  Can the extension be built without digging a basement ( only digging to below frost line for foundation/footing, backfilling and having a heated floor system? or does the new extension have to have a basement matching the depth of basement for the existing building?  The house is in the very cold climate of Montreal, Canada.

Thanks

Answer
Janine,

A full basement is not necessary; other options include piers (open below), crawlspace, or slab construction.  The foundation/footings will need to go below the frost line; for this reason, in very cold climates homeowners often choose to include a full basement at relatively small extra cost, thereby doubling the new square footage.  Your friend's designer or builder will be able to advise on the relative costs and benefits of these various options, including the impact on recommended heating system, i.e., in-floor heat or not.  I hope this helps; feel free to post any follow up questions you may have.  -Ted