Foundation question for two story addition to old home
Having a second floor 14 x 18 room added over an existing single story room on our balloon framed 1870's house by a well established contractor. The existing room's hip roof would be removed, and the new second floor floor and flat roof would be supported as follows:
Contractor plans to place four "mushrooms" below frost line supporting cement columns which then would support 4 X 4 wood beams going through the existing first floor wall. The beams would then rise to carry the load for a 14 x 18 room and it's flat, slighly pitched roof.
Support for the new floor and roof would totally be on ledger boards attached to the house (one for the new room's floor and the other for the roof) at one end, and the four 4 x 4's at the other.
There is not an acceptable foundation for the single story room. Currently the wall that would receive the 4 x 4's in the single story area is supported by four lally columns resting on cement "pancakes" 16" round and 10" deep. It remains perfectly level.
Is this pier type foundation with 4 x 4's tried and proven?