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I have a 10ft wall that spans only a third of the width of the house but is perpendicular to the 20' long 2x10s below it. One end of the wall could transfer load to the foundational wall but the rest is out over the joists with no columns or supports below. This 20' span has a beam 3' from the foundational wall and spans 15' to the next carry beam. Functionally, this wall could offer support for the floor (2x10 joists as well) of the dormer above but it only spans 2/3 the width of said dormer. It has no wall below nor directly above and the studs do not line up with any of the joists below. There's nothing special about the framing either, no double plates or studs. Any insight?

update

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Yes, the new plan really helps. Let’s call North going up. So, I see the basement bearing walls/beams run East-West and is on the South side of the stairs.

So, 2x10 joists at 16” on center will support say live load (people and furniture) of 40 lbs. per square foot plus a dead load (framing, ducts, etc.) of 10 - 14 lbs. per square foot, depending on the species and grade of lumber. This is perfect for current Code compliance.

However, the joists in the 2nd floor sitting room appears to span much further than that if you remove the wall between the kitchen and dining room.

The risk to removing this wall is that the floor will sag and crack the ceiling in the kitchen and dining room...or worse, the 2x10’s are spliced over this wall and they will fail.

So, you’ll need to do a little more investigation. On the 2nd floor, what is the distance from the South wall of the stair to the South exterior wall?

  • 2x10’s can span about 19’ and support a live load of 30 lbs. per square foot and a dead load of about 10 lbs. per square foot without cracking the plaster on the ceiling below. – Lee Sam Nov 29 '18 at 23:08
  • Ok, south stair wall to south exterior wall is 19.5 feet. After some investigation, I know two big things. The joists aren’t spliced over this wall and they are in fact 2x8’s. I didn’t account for multiple layers of subfloor on the 2nd level. Safe to assume something will have to carry the load that wall is currently holding, if 2x10’s can only do 19’. How far could a 2x8 span with the same load spec? Considering replacing the wall with a header above where the secondary beam is 4’ from the exterior south wall. – Rob Schmidt Nov 30 '18 at 2:53
  • 2 x 8’s at 16” o.c. With 40 lbs. psf Live load and 10 lbs. psf dead load will span about 12’-6”. I used Hem-Fir species and Standard No. 2 grade. – Lee Sam Nov 30 '18 at 4:13
  • Looks like I’ll need a beam in that location. As moving it north/south in line with other walls would make the span ~15’. Looking at LP’s LVL specs, I could do a 5.25”x7.25” flush beam or a 3.5”x9.25” header, but I’ll need to add a 4x6 post/column for the interior point load in the basement. Does this all sound accurate from your experience? I’m considering saving the $2500 I’ve been quoted for the header and tackling this with a carpenter I know. Trying to get my plan together before I call the code office. – Rob Schmidt Dec 1 '18 at 15:38
  • Yes, that all sounds fine, except remember you’re transferring the load to the ground (dirt). So, you’ll need a footing or fasten the posts to the walls that have a footing under them. Distributing that much load to an existing footing can be tricky. If your carpenter friend isn’t comfortable figuring it out, I’d contact an architect or structural engineer (not civil engineer). – Lee Sam Dec 1 '18 at 17:06

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