Hi all,
I am interested in having a garage built and assume that most contractors
would be using a truss system. A neighbor has a garage with “storage” or
“box” trusses so that he has some attic-type storage space. His garage has
a 7/12 roof. I would like to get a 2-3 car garage built using these types
of trusses, but to better match my house I would need a shallower angle
(6/12 or 5/12). The span of the trusses would be ~34 feet.
Does anyone know if there are storage trusses made to shallow roof angles?
If so, how much storage space would a 5/12 or a 6/12 storage truss provide?
Is there a site that has this information or a way to calculate this?
Thanks,
Bart
Replies
Bart -
Since trusses are typically made to order, you can get about anything you want. (Anything that works, that is)
There are 2 types of trusses which could fit the description you used. The first would be what I call a "storage truss". (The term varies by region, though) It would look more or less like this:
http://www.wsitruss.com/trs08.asp
The bottom chord would probably be a 2X6, and it would be designed for added storage load. the advantage of these is that they're relatively inexpensive. (Maybe 25% more than a standard truss) The downside is that you get limited storage room and headroom.
The second type would be an attic truss. (Also called "room-in-attic") The following is a relatively poorly designed example of such a truss:
http://www.wsitruss.com/trs41.asp
The advantages of these trusses are that they're basically all the framing for the room in one shot. The only real downside is the cost - They're about 2.5 times the cost of a standard truss.
The headroom you get varies. But if you figure out the overall height of the truss and knock off a couple of feet, you should be pretty close.
Also - what part of the country are you in? That may have a dramatic affect on what kind of truss will work.
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Boss,
I guess I was thinking of the second example. I can't really see how you would get much storage out of the first one you listed. I live in Virginia, so snow loads would be minimal. Is there any way I can figure out the amount of "space" available with the attic truss in a 5/12 roof with a 34' span? If it turns out to be minimal, I'd probably not bother spending the extra money.
Also, what is a reasonable load limit? I think my neighbor told me his was 20psf. Seems like that isn't really very much, and an average person's weight and distribtuion would exceed that (although he hasn't had any problems).
Thanks
Bart
Take a look at this one - It's probably roughly what you'll be able to make work.
Note that I've raised the heels at the end to try to get some headroom, but you still don't have much.
If this is all that you'll get, I wouldn't really recommend it - It just isn't worth the extra money.
As for loading - Any walkable room should be designed for a minimum of 40 PSF IMHO. I only use 20 PSF for the "storage trusses" I mentioned, and only if the ceiling height is 6' or less. Keep in mind that there are as many morons doing truss design as any other job, so you might get attic trusses with 20 PSF if you don't specify something else.
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Boss,
Thanks for the information. I assume that the diagram is for a 5/12 roof? I will have to see what I can get as far as truss design and load.
Thanks,
bart
Yup, that was a 5/12. A 6/12 roof would get you much better headroom, but probably not 8'.
To gain more headroom, you might be able to drop your garage walls a foot or so, and add that foot to the heels of the truss. That's an old trick that works once in a while. (Depends on how much headroom you have in the garage, though)
I can run something else tomorrow if it will help any.........
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Boss,
As my wife and I are relatively short, we wouldn't need too much headroom, I would say a maximum of 6' would be fine (and that is accounting for some type of light fixture). Any way of figuring what the minimum slope in a 34' span would give 6' of headroom?
Here's a 3DHA drawing of what I am proposing.
I REALLY appreciate your help.
Bart
Take a look at this one. I'm still not sure it's worth doing, given the short ceiling height.
Could be better if you can lower the walls and raise the heels like I mentioned in a previous post.
The more you complain, the longer God makes you live.
If your 3DHA drawing is an accurate depiction of your addition - with an offset ridge lower than the main house ridge - you could gain somewhat by matching the roofline of the house and supporting the section of truss overhang with post and beam. This would create a covered patio or you could just close it all in as part of your new garage, expanding the enclosed storage area. If you'll post the overall width of your house I'm sure Boss could quickly draw up something.
Ralph,
Thanks for the input. The 3DHA drawing is of a detached garage plus a workshop storage section. In any case I am not really sure I understand what you mean (although I certainly would like to increase storage space!)
Here is a webpage with the floorplan and some elevations. I would be glad to get any input offered.
Thanks in advance.
Bart
For a 34 foot span at 6/12, you will have about 7-1/2' high, about 9 or so feet wide in the middle "A" frame, or triangle. Not a whole lot.
In my house, I have a 28' span with a 6/12 and what I did was put a 4x4 piece of plywood in the "A" part where 4' was the span between the legs of the "A". I did this on both sides of my attic access. This allows me (or somebody) to crawl under this huge "shelf" and provides room for Chirstmas decorations, Summer/Winter clothes, etc. etc.