Replacing rotted lally columns in MA: Help!
Recently purchased a 1926 Farmhouse outside of Boston. Had structural engineer do an assessment before I started my planned (non-structural) renovations. From his assessment, the main support beam (6×6) is solid but the house has some minor sagging. Given the old foundation, he suggested replacing the 2 existing lally columns with 3 new ones (on new footings) to reduce the spans. (House footprint is 24×24, foundation of concrete block, 1.75 story, standard platform framing, pitched roof )
So, couple of questions:
1-He mentioned footings should be 4 ft deep. Assuming the depth is due to frost line? And is this depth correct? Reason I ask is that most articles & discussions mention footings that are much more shallow.
2-From my reading, doesn’t seem to have consensus if pad should be level to or above the floor line. Advantages/disadvantages to either? (I do intend to finish the basement someday, but I anticipate having to box in the lallys)
3-Same goes with a single or multi-phase footing pour. From what I’ve read, a multi-phase pour can help reduce any lally settlement/movement issues due to continued foundation/ground settlement. Advantages/disadvantages to either?
Thanks in advance for your advice!
Jen in MA