Expert: Dave Johnson - 2/22/2009

Question
We currently have an enclosed porch on the rear section of our bungalow, the room spans ¾ the width of the house which is 24’ and the living space is seasonal  in that there is no functional heating other than a wood stove. We live in upstate NY and would like to expand the room to occupy the full width of the house and convert the area into a year round family room. Although the room is completely finished there is no actual foundation. The room is currently supported with steel pipes sporadically space underneath and a mortared flat stone skirt around 2/3 of the porch.  My question is how or should we go about getting a foundation installed without tearing down the entire structure or do we even need a foundation? The room is structurally sound and there is no indication of any movement between this room and the main living spaces.  

Answer
Hello Ivan,
Apparently the posts (pipes) must be well into the ground, because given the amount of frost you get in your climate it would otherwise have moved by now.
So, the question becomes; do you want a foundation?  The upside of one would be to guarantee never having movement and that you might better be able to keep the floors warmer. An addition with no cellar
is going to have very cold floors. Adding a foundation might allow
you to have an in-floor type of heat.

If you opt to go with a foundation, I would suggest holding the porch in place and excavating to either a frost wall or a full foundation depth, pouring a footer then using ICF's to pour the wall.
(icf's are insulated concrete forms and are becoming ever more popular, especially for this type of job.)
You could bring them up to above grade, pour them, then finish the wall with P.T. lumber.

I hope I have answered your question, and if not, please mail me again,

Best of luck,

Dave