So we are fully gutted in our duplex and we realized that the middle wall of the building (load bearing) is set on railroad ties that apparently lay on dirt. We noticed this when trying to assess why the floors were slanted toward the middle of the building. I would like to remove that wall, remove the railroad ties, pour a footer and then replace wall with either posts or a new wall. I want to explain my plan and see if anyone spots any problems with it. We are planning to build temporary walls on both sides of basement between 36 and 40” away from middle wall. These walls will be 2x6 studs 16 o.c with a 2x8 or 2x10 bottom plate to help disperse weight (floor is dirt) we will then remove the middle wall and footer ties, dig down approx 18” and pour a new solid footer 18” deep 18” wide by the length of the house (42’) Is there any justice to pouring a footing under our temp walls? My only concern is while digging for the new footer we start to underpin the temp walls, that is why we are going 36” off the wall to hopefully avoid that. The home is balloon framed with a stick built gable roof that sits on the outside walls so I believe there is no roof load on the middle wall, only floor loads.
Ambitious project with lots of issues: 1) loads on walls, 2) temporary supports, 3) size of new bearing wall, 4) connections, 5) soil conditions, 6) size of footing,
1) I’d verify that the roof does not sit on the wall. If it does, it makes things more complicated, but not impossible. Is this a single story house? Is it located in (a.) high wind area, (b.) seismic area, or (c.) high snow load area,???
2) I like your plan of having two temporary walls...is this due to joists lapping on the bearing wall? Keeping each temporary wall about 3’ from the bearing wall is reasonable. Remember, the transfer of load into the soil is at a 45 degree angle. That is to say, the transfer of loads from the temporary wall should not impact the soil (and edges of you 18” wide trench) 3’ away. (We’ll talk about the width of your footing later.)
3) If the new bearing wall will only be 8’ or 9’ high, then 2x4 studs at 16” oc are acceptable. Will it sit on the subfloor or is that balloon framed also?
4) How the new bearing wall is framed will determine how it’s connected to the footing and ceiling (above).
5) The type of soil will determine the size of the footing, required reinforcing (rebar), likelihood of sluffing, etc.
6) I like the continuous footing idea, but it may need to be wider. (Going from a timber width to 18” seems reasonable, but if we knew more about the type of soil and total load, we could determine if it’s wide enough to support all the loads.
So, to answer your question, no, I don’t see any major problem, but if you could answer the above questions, we could help more.
Btw, a few pictures of the attic, etc. would help.