I need to remove an old plank subfloor; however, that subfloor runs underneath an exterior load bearing wall. This wall runs parallel to the joists. No idea if there is a joist running underneath that wall (parallel to all other joists). I would assume that there is. Question: is it safe to sawzall out the plank subfloor all the way to the wall, leaving only the portion of each plank that is stuck underneath the wall?
These are my thoughts on it, but I’m no expert: I do not believe that the subfloor performs any load-bearing function with that exterior wall; however, what I am worried about is that the subfloor helps with ensuring that the bottom of the exterior wall does not “pull away” from the house. If I sawzall out the plank subfloor, I am afraid that there will be nothing from keeping the bottom of the exterior wall to move laterally, i.e. pushing or pulling away from the house. What is the exact function accomplished by a sub-floor running underneath a wall?
Here is a photo of the job. No idea why the plank subfloor curves downwards as it gets closer to the exterior wall, but that is part of the reason why I’m putting in a new subfloor. The exterior load bearing wall runs all along the right hand side of the photo. House dates from 1919.
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I suspect that the planks curve downward because the weight of the wall is bending them. They're probably not bearing all the weight of the wall -- the outer edge appears to be resting on the rim joist -- but they're bearing maybe 20-30% of the weight.
(The wall looks kinda funky -- the near edges I can see look like drywall, and I see a piece of 1x2 lath (but not plaster lath) sticking out of from behind the wallboard in the first shot. So no telling how the wall was constructed, or what was done to it in the past 92 years. Some archaeology is merited before you go doing anything major.)
More info...
Thanks Dan. Please see enclosed for more detailed photos. I believe that the load-bearing is all being done by the sub-floor planks and a few 2 1/2" x 10" that are about 2' feet long, interspaced by 24-30" and which are perpendicular to the joists. This floor is on the 2nd floor of the house; there is another floor above it with a dormer window centered along the front facade of the house. All that weight is bearing down on these few elements. The sub-floor planks curve more downwards along the center of the house then on the edges; I believe this is because the two walls that are perpendicular to the front wall must be sharing some of the load that the front wall supporting structure should have been supporting.
I suggest that I should use the load-bearing-capable structure that is the located the closest to the 2nd floor wall (the one I am trying to better support). That load-bearing-capable structure would be the exterior brick. If that isn't suitable, the next available one is the interior wall form the 1st floor (see photos). It would be good to be able to use either of those to better support the short 2 1/2" x 10". Also, it would be good to better secure the 2 1/2" x 10" against the joist.
Note: the last photo of the outside of the house shows how much the 2nd floor protrudes from the house by about 9-10".
You're going to need a structural engineer to take a look at this. The cantalever is all wrong on this. It's supposed to be 1/3 catalevered out, 2/3 support side. Right now, the uplift force on that interior joist connection is 2 times what that whole outside wall and roof weighs!
I've attachec a basic diagram of what should be done, but you will need expert help in shoring up that outside wall while the worke is being done.
Basicly, those short 3x10s that are there have to connect to the next joist in... at least one more joist in, possibly 2. Take the measurement from the outside edge of the 1st floor stud wall to the outside wall of the upper floor that is cantilevered (say 12"). The next joist should be 24" OR MORE away from that wall to be of use. It would also be a beam, not just a regular joist.
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Where'd the rest of the posts go in this thread?