Expert: Ted Barnhill (Principal, Design45 LLC) - 12/5/2007

Question
I would like to have an extension built (18' x 7') in Dec-Jan in Montreal, Quebec (hardiness zone 5; nights could be as cold as -15 C or 5 F).  Could this be done given the weather condition?  Would building a Frost-Protected Shallow Foundation solve this problem?  If this is possible, how much of an increase in price should I expect (vs. summer construction)?
Thank you.

Answer
Year-round construction is possible in your climate, but there are drawbacks.  Any concrete work will require additives to ensure proper setting; this includes poured foundations and mortar in block foundations.  Some feel that winter concrete is more likely to experience failures over time.

Frost-protected shallow foundations still require pouring concrete so would not get around this potential hitch.  There are panelized (factory-built) foundations in concrete and treated wood that can be put up in a day.  The excavation would need to be protected against freezing by blankets, straw, or other measures.  

There are often winter surcharges for building, but depending on your local economy, this may still be an affordable time to build.  Overall, housing is down, and with fewer winter jobs, you may find costs to be very competitive.

Good luck with your extension, and feel free to follow up if you'd like.  -Ted