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I am planning to turn unfinished attic space into living space, however, it seems that the entire house (including ceiling joists and rafters) was framed with rough 2×4, as was the practice 75 yrs ago. I need to, for obvious reasons, beef-up the first floor ceiling joists. I can use 2×8 and 2x10s to span most of the attic space, but there is one part that needs i-joists to span about 18′ or so.
Here is the problem:
There is only 5.5″ of clearance from the inside edge of the top plate to the botton of the rafter. I cannot cut an I-joist past the inside edge of the top plate (at an angle), so nothing larger than a 6″ I joist will fit (won’t do much good).
Short of adding a beam here and there to break up the span (so I could use smaller lumber), anyone have any ideas? Raising the roof up isn’t really an option.
Thanks.
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Are you certain that those are the spans you need to cover....I would think there are some walls beneath there somewhere for some bearing and therefore breakup of span lengths.
Pete
*Believe it or not, these are the distances in a couple places. The livingroom is about 18'x12' and has rough 2x4 ceiling joists running length wise. It sounds like the easiest thing in this case would be to put a beam down the middle and cut the span in half to 9', then frame it up with 2x8s. Needless to say, the ceiling is neither flat nor free of cracks at this time. More than one person has stepped on the lath from above it seems...andrew
*Why can't you cut the I-joists past the inside of the top plate?Another way to shorten your span needs is to add knee walls in the finished attic. That would be the wall that runs from floor to rafters along the sides and is only about 4 or 5' high. You use the studs in this wall to "hang" you joists from the rafters.Pete
*Fred,I made that suggestion with standard lumber in mind for joists.Andrew, I also had another Idea. I have lots of Ideas but this one pertains to this. Is it possible to run the joists over this 18' section in the other direction so that the span is only 12'. you could tie the ends into a stacked joist (4 or 5 assembled side by side.) Is it also possible to decrease the required height of these joists if you double each up side by side for the 18' direction so that you will in effect have something along the lines of 4x? joists.Still thinking,Pete Draganic
*I've done something like you suggest with floor trusses a time or 2. You can hold the top chord back a foot or so, and have the webs run down to the bottom chord at the end. You may or may not be able to convince a truss supplier to do this - they aren't known for being flexible. I could sketch up a drawing and fax it to you if need be. It's kind of hard to describe here.
*Andrew, I gotta go with Pete on this one.Set a glue lam or something running the 12' lenght at the mid-point of the 18' ceiling below. The you can joist hang some 9' 2x6's off the sides of the glue lam supported at the bearing walls at either end. You may have to cut a hole in the roof to get the glue lam into the attic. The draw back is you loose some ceiling height. Ed.