I have appreciated your “What’s wrong with this truss #__”
Now I have a question about a particular building design, and would like to know how you would accomplish what the customer wants.
A customer wants me to build them a 32′ x 40′ garage with a gambrel-style roof incorporating a second floor with dimensions of 20′ x 40′, and with two dormers on one side. They would like to use trusses.
Can this be accomplished with a truss?
If not, how would you accomplish this?
Anyone can chime in as to how you would go about this.
Thanks,
Bryan
“Objects in mirror appear closer than they are.”
Klakamp Construction, Findlay, Ohio
Replies
This can be accomplished with trusses. If you want a clear span for the first floor you will have to use trusses or a couple of large steel beams. If you don't mind a girder running down the middle of the garage with posts supporting it, you do not need to use trusses. The roof could easily be stick framed with lumber.
You should see your local supplier for a design and a quote,
Gambrel Attic trusses are fairly common. I threw a quick design together and attached a picture. It may or may not work, depending on the loading requirements in your area.
With a 20' room you'd need a bearing at or near the center of the truss. You can make a design work with a 20' clear span room, but it will bounce like a trampoline. (Don't let a manufacturer talk you into this)
If they really want a clear span truss, the room would need to be about 16' 6" wide or less. And with a 32' truss there would still be a bit of "spring" to it, I think. Anything 32' long and made of wood will flex a bit.
Hey Boss.....what program do you use to draw with?"If 'tis to be,'twil be done by me."
We use software specifically written for designing trusses. A lot of folks ask me if we used AutoCAD. But what we do is computer aided engineering (CAE) not computer aided drafting. (CAD)Our software comes from a compine called Alpine. http://www.alpeng.com/ Most truss companies buy their plates from a company like Alpine. Then the cost of the software and engineering is considered part of a "package deal", and is included in the cost. So it's not a program you can buy "off the shelf".
There's two theories to arguin' with a woman.
Neither one works. [Will Rodgers]
Thanks for your reply, Boss. I am working with Gordon Lumber here in Ohio, and their truss plant said that a truss could not be made with the layout that my client wants, and that you have proposed. I did request it to be made for a 40# live load.
So, here is what I proposed, and they said it would work:
Use two 2-ply 16" LVL's, set even on top with the second floor, positioned under the 40' long walls of the second floor room. Span between the beams with 11 7/8" I-joists. Install 3/4" t&g ply on for the floor and to extend onto the tops of the beams. Use an 18/12 pitch truss on each side, which will set on top of the ply and a bottom plate, and would also be the second floor walls. Double plate the tops of these walls, then install a 4/12 pitch x 20'8" gable truss on top of the walls. The 16" 2-ply LVL's would have a bearing point 16' from one end, as there will be a dividing wall on the first floor. This building is a garage/workshop, with the second floor space available for a family room/craft room.
Hope this clears up any questions anyone has as to the design.
Thanks,
Bryan
"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio
Edited 4/6/2005 10:41 pm ET by Bryan Klakamp
I wonder why they said they couldn't build a gambrel attic? I wonder if maybe they just didn't WANT to for some reason. Did you ask for a 40# live load on the roof, or on the floor of the attic? Sounds too high for the roof in your area, but appropriate for the floor. What they're proposing sounds like it could work. (Although I would want to see it before I would say for sure) But it also seems like a lot of labor and $$$.Have you thought about asking another truss company?
My Wife is so frigid when she opens her mouth a little light comes on. [Benny Hill]
The 40# live load is for the floor.
I believe you said in a previous post to not let anyone sell me a truss like the one you posted without a center bearing point, because it would be too bouncy.
Also, the two beams will be 3-ply 18" LVL's.
Spoke with a gentleman from the truss plant today. Showed him your drawing. He said we would need a good-sized beam for the center bearing point. He could not tell me exactly, as he would have to calculate it. By doing it the way I described, there will only be approx. 6" of beam extending below the ceiling.
I have not asked another truss company. Gordon Lumber is really the only true lumber yard in this area, other than three big-boxes. We do have an 84 lumber, but I prefer working with Gordon. They have helped me on other projects, and I appreciate that.
Thanks, Bryan"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio
I wouldn't do any kind of truss without a minimum 40# live load on a floor. And I don't blame you for sticking with a company you've grown to trust. But I do wish they'd be a bit more flexible with you.
Thank you for sending me a copy of your book; I'll waste no time reading it [Moses Hadas]
Do you have any other suggestions as to how I should frame this building?
And, to show my ignorance, what is a parallel chord truss?
Thanks"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio
Tha gambrel attic trusses were my best suggestion. The only other thought that I have which might help would be to make your LVL beams flush. If they're not in the "room" part of the structure, the bottom of them could be flush with the rest of the framing.
We grow in character through service. [Augustus Thomas]
I would like to make the LVL beams flush on the ceiling side. But, there will be two dormers on the one side. Since I will not be able to make that one flush, I might as well not make the other one flush. I am also going to run the plywood subfloor onto the top of the beams to help tie everything together.
And, I took your suggestion and met with another truss supplier today. I had some time, and was right down the road from them. He will have something for me in about a week. We'll see what he comes up with.
One further question: What is a parallel chord truss?
Thanks,
Bryan"Objects in mirror appear closer than they are."
Klakamp Construction, Findlay, Ohio
This will answer the question and give you some idea of what's what with trusses. It's a pdf, 24 pages and takes a while to load (I'm on dial up).
http://www.ufpi.com/literature/siteprodtech-104.pdf
A parallel chord truss just means that the top and bottom chords are parallel - Like a floor truss.
Why do people pay to go up tall buildings and then put money in binoculars to look at things on the ground?
Ron
Would using a parallel chord truss in place of the single member bottom chord remove the need for center bearing? Would that be something that could be made a part of the gambrel attic truss?
"Would using a parallel chord truss in place of the single member bottom chord remove the need for center bearing? Would that be something that could be made a part of the gambrel attic truss?"
Maybe. But there are some disadvantages to that.
First would be that it adds a lot of depth to the floor system. That also means that to keep the room the same height, the truss has to be taller. That can mean the difference between piggybacking the truss or not.
Also, this can add a lot of pieces, which means a lot of added cost.
I've probably only done one or 2 like that in 20 years, for those reasons.
There are very few problems that cannot be solved with a suitable application of high explosives.
Boss could you span farther if the bottom cord was a truss joist design??
Kinda combine a parrallel chord floor truss with a attic truss.
I'm not a truss designer, I just play one on TV :)We always get it right!!!
the third time....
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"Almost certain death, small chance of success.... What are we waiting for???"
Ralph Wickland alread asked that. See post #9 in this thread.
She is a peacock in everything but beauty [Oscar Wilde]
saw it right AFTER I hit the post button!!!
DOH!!We always get it right!!!
the third time....
<!----><!---->
"Almost certain death, small chance of success.... What are we waiting for???"
Well, it hard to be good looking AND brilliant. The world just can't expect too much out of guys like us.(-:
A conclusion is the place where you got tired of thinking.
The 30' by 42' shape is highly economical for spanning the entire distance with steel framing, such as open bar joists.
Another suggestion would be to use light gage steel framing to form your trusses.
Also, you could span the 32' direction with a couple of steel beams and then frame between them with conventional wood joists and build the roof with whatever method is most economical. Steel beams of sufficient size are often found at steel scrap yards at greatly reduced rates.