For a loft floor I have a 24' span and I want joists to be 24 O.C. and no center support. Should I use I-joists or LVL. Also does anyone know PSF for floor? The roof will sit on knee wall on top of floor directly above 2x6 first floor framing.
Tom, I hope PEG jumps in on this one.
I had the same problem with mine. LVL isn't what it's cracked up to be IMHO and I wouldn't use it for that span. I was going to build my own laminated beam with a 1/4" steel core.
Finally, I shrunk the loft to 12' for a number of reasons. The span is certainly doable, but I wouldn't be comfortable with it without a support.
Your live load for a loft is 35psf and normally you would use 10psf for dead loads so size for a 45psf total load. Here's a preliminary calculation for rough sizing.
For a 24' span you should go no more that 1/360 for allowable deflection. At 24" o/c that would be 90plf to the joist. For an LVL you could use a 1.8E 1 3/4" x 14" (from GP Lam book 1997 - only chart I have that can be used this way. So, check w/ local supplier).
Thanks guys...are I-joists stronger than LVL's apples to apples and which is more cost effective. I will be be trimming in beams so it doesn't matter which I use.
I used 16" I-Joists to support bedrooms over a 26' wide garage. They worked well and the bedroom floors are solid. Floor trusses would also be a possibility but they seem to cost quite a bit more per foot that I-Joists.
Jerry
When you factor in trimming out I-Joists for appearance are LVL's now more attractive cost wise???
Don't forget to take into account the weight difference....an I-joist would be much, much lighter!!! A 24' LVL? Yikes, that is gonna be heavy!! :o