2x8s or I-joists (TJIs) for my floor framing
My floor joists don’t need to hold insulation (unless I add some later for sound insulation) because my crawlspace has insulation outside the stemwall.
I could use 2x8s at 16 o.c. and spend $612 on lumber. Or I-joists 9.5 inches deep, 24 o.c., and spend $894.
-Are I joists kinder to the planet? In terms of trees used it seems like yes, but what about processing footprint?
-Are I joists a lot easier to use? I know they’d be lighter and more uniform than 2x8s. 2x8s can vary a bit in depth, but it seems relatively easy to modify the depth at the joist hanger if necessary so that all match. More annoying to deal with: twist, bow, cupping, etc. Might it come down to the quality of lumber I can get? I can get kiln dried 2x8s. I know to put all joists crown up.
-cost of hangers seems comparable. I’m hanging the joists from the sill plate using top flanged hangers, which apparently has the advantage of eliminating a rim joist, which is apparently expensive for I-joists.
-2x8s give me a little more headroom in the crawl space. but I’d still have about 30 inches even with the I-joists.
-the joists will be ~18 feet long, with a beam to support in the middle. Plans don’t seem to make clear but I assume the beam is under the joists, not at the same height (so not requiring joists to be cut).
-since crawlspace is conditioned, I think plumbing and electrical won’t have to be punching through the joists. (I believe I joists are easier to poke holes in than 2x material.)
Are there other things I should consider? I look forward to getting some more perspectives.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part