Expert: Ted Barnhill (Principal, Design45 LLC) - 3/4/2008

Question
I live in a townhome (built in 1860)in a downtown area of an upstate New York city.  I would like to add an addition (apx 16' by 16') to the back of the house.  There is no access to the back except through the house. The addition would be on the first floor level where a deck (on posts)stands now.  There is a basement apartment that has a rear egress that comes up next to the deck.  Two questions:  1) Is a pier foundation an option in this climate?  2) Should I expect that contractors' estimates will be higher than usual because of the necessity of bringing materials through the house and, perhaps, modifying usual construction methods?

Answer
Eileen,

You have a very unusual situation!  I am curious why you couldn't have contractors use the rear access route that the basement apartment uses.  It will certainly be much more difficult, and cost more, to build an addition "from the inside."  Excavation and foundation work is typically done by heavy machinery; in cases where anything must be hand-dug, or concrete placed without truck or boom access, costs and time to build would rise dramatically.  

A pier foundation is certainly possible in your climate.  Floors can be insulated well with modern foams, but you'll have to be careful with any plumbing you intend to run in that area.  Depending on your soils, and the difficulty of getting quantities of concrete to the site for your footings, your contractor may consider helical steel piers.  These are a premium product but require no concrete so may help in your unique situation.

Good luck!  -Ted