I’m a DIY’r and first-time poster here (did plumbing for a living eons ago) putting together a materials list and estimating costs for an addition, and deciding on either timber or manufactured joists. Floor sizes on the three-room addition will be 22X24, 14X34, and 8X10 over crawl space wood foundation. I’ll contract a carpenter and crew for the foundation and framing through dry-in, and plan to assist with as much as possible (this is agreeable to the carpenter as I’ve worked with him on other projects)
Subfloor will be 3/4″ T&G plywood or OSB. I’m assuming the 22X24 ‘ room will have a center beam with joists spanning 11′, the 14×34 and 8X10 rooms are configured in a “L” shape. Question is: Would you recommend DF joists or i-joists? Can I span 14’ with a reasonably sized i-joist or would I be better off with a center beam and timber joists? Carpenter is familiar with both, but I’d appreciate input from this board.
I’ve surfed around a bit on the DIY sites and find this one, although not really aimed at DIY, to be much more chock-full of information I can use. Thanks in advance for your advice.
Replies
With 14" tji's 12" oc I'm spanning 24' and topping it with 3/4 ply and 1 1/2" gypcrete. So yes, you have tji's as a reasonable option. Don't have the tables in front of me. Lots of reasons to favor one or the other, just as people favor Chevy or Dodge, but they each can do the job.
just as people favor Chevy or Dodge
Or Ford *G*View ImageGo Jayhawks
Because this is ground floor over a crawl space, you have the advantage of being able to put in mid-span support pretty much at will. The earth is down there, and using it will save you money. Probably 2x6's at 16" OC with spans held under 9' will pencil out to be your most cost-effective solution. Check with your building department and see what they require.
-- J.S.
real simple ---
Go to your I-joist supplier and they will do the specification for you.
Take your floor plans, and design loads (usually 40#/sqft).
Ask for the directions. Read the directions. Follow the directions.
The contractor's lumber yards have people who will spec the joists for you. The big box stores send you to the distribution yard.
Every brand has slightly different span tables. Every brand has different assembly directions.
I'lll go with John Sprung on this one. No need to spend the money on TJI's when you don't have to. Save a little on the floor and spend it on another part of the project.
Greg
You could probably do this with either. G was right that it can be engineered for free by the supplier. There are at least three different types of I-joist for differnet load and span applications. They range from 1.5" wide to 3.25" wide and have some differences in the web thickness too.
I-joists will cost more in material but you can make that uyp in labor really quickly unless the crew is unfamiliar with them or unless there are peculiar quirks in the design.
Take the plans you have so far to the supplier and let them recommend and quote a package.
Excellence is its own reward!