Thread: I-Joist Spacing

I'm seeing I-joists spaced at 19" on center. Whats with that? Why not the normal 12, 16 or 24"?

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Originally Posted by John Dirks Jr

I'm seeing I-joists spaced at 19" on center. Whats with that? Why not the normal 12, 16 or 24"?

Dyslexic Builder????

Originally Posted by James Risley

I-joists can be sized for 19.2" centers. This allows one less joist in 8 foot and can still use regular 8 foot plywood/osb. Note that there will be no joist at 48" so the stagger will occur at say 38.4 inches. Look at your measuring tape some but not all have a black diamond on the tape at 19.2", 38.4", etc. This is to aid the framer.
JR

I stand edumacated. Just checked my tape. At 19.2 theres a little black diamond. I never had seen it before now. Thanks.

Originally Posted by James Risley

I-joists can be sized for 19.2" centers. This allows one less joist in 8 foot and can still use regular 8 foot plywood/osb. Note that there will be no joist at 48" so the stagger will occur at say 38.4 inches. Look at your measuring tape some but not all have a black diamond on the tape at 19.2", 38.4", etc. This is to aid the framer.
JR

What James said, plus: We often use roof trusses set at 19.2, it takes the wavy look out of the roof when the sun is at the right angle and you don't have to use clips for the sheathing.

I have never seen floor joist at 19.2" or 24" oc. but I-joist like trusses (roof or floor) are designed by an engineer, so if installed per drawings will meet code. I think that I-joist are a great solution for second story floor systems that span over large first story rooms, sure beats the I-beams and flitch plates we had to use. I-joist, especially longer spans, do have some deflection, so while the 19.2" may be acceptable IMO it is not the best way to keep the dishes from rattling in the china cabinet when you walk across the room.

It's all based on design and load 12",16, 19.2, 24, all work if designed properly, sometimes getting the insulation to cooperate is another thing.

We have used 19.2" spacing for floor trusses. It's a little more efficient and can save some costs on a large building.

I have done 19.2 centers a few times... designers idea not mine. I didn't really care for it. Really doesn't save much time or material. Just a hassle getting 16" wall studs to stack.

As an insulation contractor, I hate this..."special order" for fiberglass batts and correct size lightning rods (supports)....so the framing contractor can save a joist or two....and use the little black diamond on their tape measure

Originally Posted by Larry Morrison

As an insulation contractor, I hate this..."special order" for fiberglass batts and correct size lightning rods (supports)....so the framing contractor can save a joist or two....and use the little black diamond on their tape measure

Just curious, is the overall cost of furnishing and installing "special order" (19") insulation actually more or less than standard insulation (16")?

Originally Posted by Rich Goeken

Just curious, is the overall cost of furnishing and installing "special order" (19") insulation actually more or less than standard insulation (16")?

Where we are it is just a few cents more but the real pain is a contractor that awards you the job and then wants it done tomorrow because he has scheduled drywallers the day after tomorrow...In larger cities 19.2 inch batts probably aren't that big a deal to get. If it is a small job, many times we have used 23" batts and "made them work".

We mainly do blown cellulose both walls and ceiling/attic (because fiberglass is crapola-- IMO) we don't stock fiberglass as a rule.

With construction being as slow as it is now many places aren't even stocking a good supply of standard size and R-value batts. So that also comes into play.

Everyone needs to have this I-Joist pocket guide on their computer or wherever. It is for Weyerhaeuser joist but all brands have similar requirements. I could not upload the file due to the size but this is the link to the document.

http://www.ilevel.com/literature/TJ-9001.pdf

Ditto on what Scott said. Look around on job sites. They are left laying around all the time.