Cottage - foundation type

[cmarines]

Hi All,
I would like to extend my small cottage (actual area size 13' x 12'),
situated on cold climate forest hill area.
This is a very small cottage, cathedral roof, no basement, only one
floor. The actual foundation is based on post and pier foundation
(slab, flag stone).
So, I would like to keep the existing cottage and to build another
construction as an  "extension" for more room,  wood framing, the new
area would be 20' x 30', also one level, cathedral roof (eventually
mansard), no basement
My question is regarding the type of the foundation for the new
construction(extension).
What kind of foundation should I use for the new extension? Should I
keep it the same as the actual construction? Or I should go with
foundation that the bottom of the footing sits on soil that is below
frost depth. Which is the solution you suggest?

Thanks,
Chris

[jraabe]

The first thing to do would be to assess how the existing foundation is holding up. Are there any signs of frost heave or settling? Are the floors and roof level? Do the doors and windows stick?

If the current foundation is solid and giving good service you can probably do an updated post & pier extension such as shown in my free report: http://countryplans.com/foundation/index.html.

If not, or if the building department has other requirements of your addition, then you are probably better off lifting the cottage and putting a new concrete perimeter foundation under both the new and old sections. Then you will be able to re-level the old section and add on with confidence.

[cmarines]

Thanks for reply John. The actual foundation seams to be pretty stable. From the previous owner, I understood the requirement is to keep the same type of foundation (post & pier). If I go with the same type of foundation, will this be adequate to hold the cottage "extension" (with a surface 20' x 30')?
May I attache some pictures of the existing cottage and also some draw with what I plan as extension?
Thanks again.