Should I use joist sisters that fully span support beams?

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hepcat72
Posts: 6
Joined: Thu Apr 13, 2017 4:18 pm

Should I use joist sisters that fully span support beams?

Post by hepcat72 »

My house was built in 1920. We're down to the studs in our second floor DIY bathroom remodel. I plan to sister the joists to level the floor for tile. It dips over an inch in the middle, and it squeaks in places.

I have a problem however. I thought I would be able to install joists long enough to rest on the support beam of the exterior wall all the way to the next support beam in the middle of the house, but looking at it now, the next solid support (a first floor wall) is 4' past the wall with the hall closet. There's no way I can get a full length joist sister in there.

So I'm trying to decide whether I should partially demo the closet to install support/beam-spanning joists or just screw the sisters into the current joists.

I don't know how well advised or ill-advised it would be to not fully span the supports. How do I decide whether I should demo the closet?

The joists were sistered on the bottom with smaller beams by the previous owner to level the kitchen ceiling. I don't yet know how far they go, but they are much smaller than the original joists (which are the heftiest pieces of wood I've ever seen, honestly.

I know the wood in this house is very dense and hard to get a screw through. Supplemental question: when I sister, should I use bolts or screws, and what kind/size? If I do screws, I imagine I will have to drill guide holes, otherwise, I won't be able to get them in.

hepcat72
Posts: 6
Joined: Thu Apr 13, 2017 4:18 pm

Re: Should I use joist sisters that fully span support beams

Post by hepcat72 »

You know, the previous owner is the one who remodeled the kitchen below and he's an electrician. I'd pinged him about power lines a month ago or so and I'd mentioned sistering the joists WRT the power lines running through holes in the old joists and he said to just notch the sisters instead of redoing the wiring because I only wanted to level the floor.

He has seen those joists from below, so if I assume he knows about carpentry and structural issues, then it suggests I don't need to span those beams...

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