Hi All,
I’m doing some new year planning and that includes a new detached garage with a second-floor studio. Structure will be 24 x 28. I want to clear span the garage for workshop reasons so I’ll need floor joists that will span 23′-6″ without support. I like how easy it is to band block the truss joists when I’ll have rafter tails hung out over the top plate but the TJIs are cheaper. I know some folks here hate the truss joists but I’m thinking detailing will be much easier especially since I will have to double a few for the stairwell opening.
Your thoughts?
Tim
Replies
Floor trusses
I would usefloor trusses.
You are probably going to be speced 13" tall on a 19.2" centers.
Wood joists would be a minimum of 14" on a 16" center.
As much as I love I-joists, the longer spans (over 20') result in a stiffer floor with trusses.
Your local lumber yard can help with the specifications.
Terry
Floor Trusses
Hi Terry,
By floor trusses, I assume you mean Truss joists and not TJIs?
Yes, but the term Truss joists is not the typical name for them around here.
When I see the phrase Truss joist I first think of the name Truss Joist Macmillion (sp?), one of the first manufactures of wood I-joists.
Terry
Thanks & another thought for anyone
It seems everyone has a regional name for anything . . . like rim joist and band joist (banding).
Another thought I had after reading one of Mike Smith's posts:
I might be able to get out even less expensive if I just run an LVL and use dimensional lumber for joists. I could run the beam across the 24' width and use 14 foot 2 x 10 SYP joists and maybe hangers to keep my full 10' ceiling height.
Tim
If you want to clear span that and have a decent floor, the floor system needs some depth to it. To span a 24' wide garage I'd want to see something 16" deep.
Either I-joists or floor trusses would work. Just follow the receommendations of the manufacturer.
Several eyars back I did a thread about floor vibration. I'd recommend reading it before you make a decision about the depth of your floor system:
http://forums.finehomebuilding.com/breaktime/general-discussion/floor-vibration
If you're doing a 1.5 story design, you might consider attic trusses. Just make sure you observe the same rules of thumb about length over depth ratio for the room suze.
Thanks, Boss
I was leaning towards the TrimJoist (floor trusses with trim on the ends for rafter tail cuts and such) for ease of use. I know they're going to be 14" deep but I haven't done framing in 10 years and, although I still have all my necessary pneumatic and power tools and such, dimensional lumber is much easier to wrap my mind around. With all the squash blocks, web strengtheners, band joist issues and then having to frame and sheath the floor before setting rafters, not to mention figuring our how to double load bearing and point bearing joists with I-beams.
Trusses would be great if I had the studio mapped out but the roof will be a double gable/pent roof design and that's easier to frame with sticks.
Cheers,
Tim
I have several comments.
No way would I recommend using 14" deep floor trusses to span that far. Did ya read the thread on floor vibration?
There's no reason to pay extra to get trimmable ends. Those are for angled walls or other odd situations. Just have them made the right length with a notch in the end for a ribbon board.
I don't understand your description of the roof style. However you frame it, make sure there are no roof loads applied to the floor trusses unless they're specifically designed for it.
You don't need squash blocks, band joists, or web stiffeners with floor trusses. Strongbacks are recommended, but they're no big deal. Just slide a couple of 2x6s in through the webs before you close in the ends.
L460 Span Charts
say I can use a 14" 560 or 360 TJI or a J14 TrimJoist to span the 24' dimension no problem. L460 should be plenty stiff for a studio above a garage and have enough live load left over for a small dance party.
As for my jumbly description of the roof; it's a gable roof running east-to-west on the 28' run with a dormer-gable on the south (front) that extends from the gable roof peak, and a full-width shed dormer on the north (rear) side.
Strongbacks is a term I've heard but not real familiar with. Are they the same as web stiffeners? Again, regional terminology confusement requires some translation.
Cheers and thanks for the help,
Tim
Listen to Bosshog. He knows more about wood trusses than most anybody on the forums. It's his career.
Here's a good drawing of a strongback in a floor truss:
http://www.chamberstruss.com/terms/Strongb.htm
Your post started out with "say I can use a 14" 560 or 360 TJI or a J14 TrimJoist to span the 24' dimension no problem."
I assume you left out who told you that. But I don't really care. My recommendation to use deeper floor members is based on a lot of years of experience and research. As a result of that research I'm very conservative on floor design. Not everyone is.
Whoever told you that was O.K. probably believes it. Ask them if they can tell you the frequency the floor will vibrate at. That will give you an idea if they know what they're talking about.
Thanks again, Boss
I think I'm coming to a better understanding now. I went to a factory in Brevard where they actually build these things and learned pretty much what you're imparting here. While I hadn't planned to do more than use the second floor space for myself, I am going to rough in plumbing and such for future use and if someone down the line builds out for a mother-in-law apartment the stiffer floor will come into play when you start adding partition walls and furniture and appliances.
So thanks, again for the lessons.
Tim
I'm glad I could help.
???????????
TJI stands for Truss joist International
Their patent wore out so now lots of people make truss joists but they are basically the same thing
Is it open web floor trusses you are thingking of comparing to? I prefer thoise when running utilities throught them, but for a simple garage see no need.
As for rafters - what you can do is lay a plate across top of the floor system, then mount rafters to that. Works the same with either type of truss.
Hey Piffin
Sorry for confusion, a lot of guys I used to frame and finish with used the term interchangeably and I guess it stuck with me. When I said truss joist I was thinking of something along the lines of TrimJoist or TrussJoist. TJI were pretty much anything that looked like an I-joist, like this:
http://www.woodbywy.com/floors/f_TJI_joists.aspx
I'm leaning that way but I've read some threads here over the years that weren't too kind to them. I do like buttoning everything up without drilling a bunch of wire and plumbing chases.
Cheers,
Tim
We do quite a few garages with living space over, clear span below. I prefer to use a steel beam across the full span and then use conventional framing. Easy, inexpensive and you'll have a stiff floor for years to come.
Hmmm . . .
There's another thought, but extra steps also. I guess there's still no easy way out.
A few years ago, I built a house with a 30' (w) x 26' (L)clear span garage as part of the structure. I ended up using 9.5/12 attic trusses which gave me a very good size room above with 8' ceilings and around 6' 6" headroom at the sidewalls. The trusses were spaced 24" OC. When I figured the extra cost of the trusses over materials and labor for framing a floor, sidewalls and roof, there was not much difference and the actual time savings were quite significant.
A few years ago, I built a house with a 30' (w) x 26' (L)clear span garage as part of the structure. I ended up using 9.5/12 attic trusses which gave me a very good size room above with 8' ceilings and around 6' 6" headroom at the sidewalls. The trusses were spaced 24" OC. When I figured the extra cost of the trusses over materials and labor for framing a floor, sidewalls and roof, there was not much difference and the actual time savings were quite significant.
Thanks for thinking of options . . .
It's just me and a front loader up here on the mountain so smaller pieces would be easier on the old back. I'm kind of a loner when it comes to projects, although I do have friends who are always willing to help. I've seen their nailing patterns though . . .