The basement under the original house is 6' 7". Not impossible but I have been in a house where they dug the basement floor down to get nearly 8' ceilings and it changed the quality of the space enough that I would bear the cost to try and get a little more height. I have popped the house to 2 story 10 years ago and did a 16' addition on the back that included a basement addition that has near 8' ceilings. You have to walk through the short part to get to it. I have a father-in-law and 5 brother-in-laws that are all 6' 5"
The house is a brick 1923 bungalow in Denver. The basement walls are 14" poured concrete on a roughly 14" spread footer. I know that sounds wierd but I have confirmed that the walls are poured on a seperate footer that is roughly the same with as the foundation walls.
The concrete foundation walls are about 4' above the floor and then they change to triple wythe brick laid with a weak lime and sand mortar that was popular in that era. The above grade walls go to double wythe above the joist pockets. The floor is 2 1/2" to 4" thick and the bottom of the footer is is roughly between 2 1/2" and 4" below the bottom of the floor slab.
I have a room that is 27' x 12' wide that I would like to get down at least 10" making the ceiling height 7' 5"
I have checked the options and I can underpin the exising foundation which I will have to have someone else do and is very expensive.
The other option from an architect friend is digging down flush with the outside walls below the foundation and pouring a 4" reinforced wall next to the foundation and below it. Sort of a retaining wall. And pouring the floor up against it to hold the retaining wall and earth below the foundation. Since it's 4" I can frame the wall right on top. I can do this which is less expensive that undepinning.
I understand that I can go down at a 1:1 but I don't want to lose the 10" in an already narrow room.
Those are the two ideas I have so far. Has anypone got any great ideas or comments on my two?