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How far can you run ceiling joists

WadeH's picture

My question is this, how far can you easily span your ceiling joists. I going to build a gargae/shop, built like a garage but it will be my shop, and most of the people that I have talked to want me to use truses instead stick built. I thought with a 10:12 pitch it would leave room upstairs for storage, office, or for any use. My idea is just 24x32. If 24' is to far with out a support wall is there is reasonable alternative. Cost is a factor, I do not want to double my cost just for a small room up stairs. Any ideas would be greatly appreciated. Thanks.


(post #98347, reply #1 of 7)

To span 24' you'd need deep I-joists or a beam down the middle.

Attic trusses are expensive to buy, if you only consider the cost of the materials. But the labor is a lot less than conventional framing.

If the upstairs room is too expensive, you might be able to simply make the building bigger for roughly the same amount of money.

When everyone owns everything no one will take care of anything. [Aristotle]

(post #98347, reply #2 of 7)

First of all, if you're talking about using that attic space, you're not talking about ceiling joists at all, you're talking about floor joists.  You'll need either attic trusses or I joists to span that far without another midspan carrying member like a wall (not such a good idea) or a carrying beam... most likely with lally's (not such a bad idea.)

You've got options, but you're not going to span any conventional framing lumber that far without midspan bearing.

Best bang for the buck would be to have an LVL or similiar midspan beam sized by your lumber supplier... to keep it cost effective you'll probably want a lally or two to break up the span and keep the cost of the beam reasonable.  Then you can probably joist with 2x10's.

This is not engineering for you, but I just built a garage as part of a house I framed.  It had a center beam clear-spanning the 24' garage... it was  5 1/4" X 24" X 24' and carried the 2x10 floor joists similar to your arrangement.   I can't imagine the size of the monster you'd need to clear span 32'.

Do you have an architect or are you winging it?

EDIT:  It wasn't a triple 5 1/4" beam.... it was a triple 1 3/4" beam = 5 1/4"!!  Good thing I'm not your archy!   LOL.

Edited 5/24/2005 7:07 pm ET by dieselpig

(post #98347, reply #4 of 7)

No Archy just kind of winging it. Spent allot years in contruction years ago. I live in South Georgia, as long as you stay close to the Southern buliding code, they are not to perticular what you do. If you know what I mean. I have just about got my wifes permission to build it, so I am trying to have everything ready when she does. :) I thought the up stairs would be just an added benifit. Thought maybe a dark room for her or something like, but the upstairs is not manditory. I have a program that was given to me called PUNCH 3000 and have been playing with that, but it basicly just gives you a basic plan since it knows none of the basic rules. I figured it would take a beam to make it work, but a 32' would take an army to raise. Thanks for you help.


(post #98347, reply #6 of 7)

Why would you run the beam the 32' way and not the 24' way?

Joe Carola
Joe Carola

(post #98347, reply #3 of 7)

Your title is about cieling joists, but the nature of your project calls for floor joists. What's the difference? About 30# / sq ft.

Unless you want a beam with 2 or 3 posts bel;ow, order attic trusses designed for the project.



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(post #98347, reply #5 of 7)

You are right, I miss spoke before. But if you are downstairs and looking up they are still ceiling joist, and if you are upstairs and looking down they become floor joist. It is amazing how that happens. :) Thanks for your help.


(post #98347, reply #7 of 7)

Wade, I have framed a garage similar to what you are describing, in which we used I-joists to span 24' (why I don't know, there was no living space above and a 6/12 roof). These were either 12 or 16" deep, 16" OC. I have also framed a garage with a 24' span and a bonus room (small, mind you) using 2x12 #2 at 12" OC. BTW I'm in lower Alabama but we use the IRC.

If I were you, I'd find out what size I-joists are needed to span the 24' and use them. You will still have whatever ceiling height as the height studs you plan to use (i.e., 8', 9', etc.) but your exterior walls will be 12-16" higher. Which in turn the siding materials you use may extend several courses above any windows and doors you plan on having.

Of course, if you used trusses, you could just build bigger and the cost difference would more or less even out.

Jason Pharez Construction

   Framing & Exterior Remodeling

Jason Pharez Construction

    Framing Contractor