Sorry for the long post — this is complicated without pictures.
I am working on an old, old house for my mother in law. I’m good with general carpentry — putting in replacement windows, hanging kitchen cabinets, but I’ve come across something I’m not sure what to do with, and I have some contractors coming soon for plumbing and HVAC, so I need to figure out if I can resolve this quickly, or if I have to push everything back.
The kitchen and mudroom sit in a 12X24 single story portion (each room is about 12X12). In pulling down some of the old basement ceiling to prep for the plumbing work, I noticed that the floor joists (which run the 12′ width) do not actually sit on top of the foundation (this would explain why the kitchen floor is like a trampoline). The house is 150+ years old, and the joists clearly used to be notched into a beam, but somewhere along the line, the sill was replaced and the notches go nowhere — just hanging in space.
Someone put in one 6″ steel i-beam to reinforce the floor (the sub floor is old barn boards, so pretty strong), and then nailed 3′ extension 2X6s from the “floating” joists to the sill plate (so, these “extensions” sit on the sill, and then are sistered for about 2-3′ to the joists).
Here’s my issue — without completely pulling up everything and starting over, I’d like to stiffen and reinforce the floor from below.
I am thinking of either adding more 6″ steel i-beams running the 12′ length of the floor between the existing joists OR I could build a new beam on either side of the basement running the 24′ length, to catch the joists (so, the joists at both ends would sit on a bean, which would sit on columns that would sit on new footings). The joists themselves are large (varying from 2X8 to 4X8 across their 12′ span, maybe 20-24″ on center), so giving the joists something to rest on would help reinforce them.
What would the space o.c. need to be for 6″ steel ibeams to strengthen the floor to an L/360 deflection? Anyone have any advice or alternate ideas?
Replies
It sounds like you are saying that these joists are 24' long?
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What does the foundation look like in the area directly under the ends of the joists? Is it solid concrete? If so, you could fasten 2X12's to the foundation with a few large concrete anchors, to support the joists.
Edit: You'd need a hammer drill for that. You should be able to rent one.
Edited 11/7/2007 4:43 am ET by Hudson Valley Carpenter
Good question. The foundation is, unfortunately, field stone.For Piffin: the joists are 12' long, and run the width of the room. The room itself is 24' long.
The foundation is, unfortunately, field stone.
In that case, I'd probably just build a standard 2X4 wall, single PT plate on the bottom, double plate on the top. Install close to the stone wall. Maybe add a shelf system to take advantage of the wood framing.
Edited 11/7/2007 10:20 am ET by Hudson Valley Carpenter
Can you add a steel beam under the notched ends of the old joists?
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