Roof Truss Question

[ALHILLDIRT]

I'm planning a Shed type storage building that will use a right angle triangular shaped roof truss, and need some help from the engineering types out there to size the materials. Will be using standard spruce 2x from the lumber yard. The bottom chord will span 20 feet. The top chord would taper from flush at one end, to a height of 5 feet at the other end. Would like to use 4 foot spacing on the truss. 2x4 purlins on edge, and a metal roof. Snow load in Alabama is minimal. I can get a 20 ft 2x6, but haven't found 2x4's that long. Which makes me think I'll need to splice the top chord. Anyone have any thoughts on the dimensions on the lumber to use or links to information on truss like this?

 

[Lasgambler]

The Truss you want to build is called "A Monotruss" It is O.K. to splice top or bottom cords. However it takes an Engineer to make the call where. Splices are put together with "gang nail plates" The truss plant uses a press to install them. The gang nail plates at the Big box stores are stamped with "not for use on trusses" Probably a liability thing to keep the novice from building trusses.

I take it you are in an area with no inspections. You need to find some engineered trusses like you want, take a picture Print and scale your picture. Or you can get and estimate from a big box store, Tell them you need the "Truss Calcs". You will get a drawing you can build from. Terry

 

[CurlyDave]

Look up a truss place near you and get prices.

When I built a roof for a much smaller shed than you are looking at, I got all the trusses made up for me for less than the materials to build them myself. Plus they did the engineering calculations and gave me a stamped drawing of the trusses.

I think the secret was they get the wood wholesale and do the calculations for free.

Mine were small enough so I could pick them up myself in my own truck, which saved a bit on delivery charges.

 

[Lasgambler]

Good point CurlyDave, My work requires Engineered trusses with Calcs. I could not buy the material and use my time to build them for what they cost.
Terry

 

[kenmac]

when I built my garage. My father in law talked me into building my own trusses ( he is a retired engineer.) I should haver listened to him. They were alot of trouble to build ( trying to work with all the twisted lumber ) & by the time I figured cost of my mat/labor I lost $. Next,,I built a 12X24 shed . I ordered the trusses for this & very happy I did

 

[woodlandfarms]

We were going to build our own trusses for an overhang, got a lot of expert opinions. But with this economy, truss companies are cutting prices and you may find a better and easier deal to go pre-made. We did.

 

[ALHILLDIRT]

Thanks for the feedback, I have so much useless information stored in my brain, I couldn't remember what this type of truss was called. This is just an add on for equipment storage and we don't have building inspectors snooping around out here in the country. I hadn't checked the prices of a fabricated truss yet, but if I go with a fabricated unit, will probably go with steel. I've got a calc sheet on a 40' 4-web truss, could I not use 1/2 of this for my mono?

By the way for those interested in farm buildings this is a good refrence site

Free MWPS Building Plans Information Page

 

[yooperdave]

You first need to find out how much load you need to support. Dead load, live load, etc.

I would buy some i-series joist (TJI or similar) and be done with it. Build 1 wall taller than the other for the necessary pitch. The joist are light weight, and come in any length or depth you want. Bevel your bearing wall plates and provide Simpson connectors. The mfr will also have published load tables which you can justify your design.

Good Luck,

Yooper Dave

 

[CurlyDave]

I would buy some i-series joist (TJI or similar) and be done with it. Build 1 wall taller than the other for the necessary pitch. The joist are light weight, and come in any length or depth you want. Bevel your bearing wall plates and provide Simpson connectors. The mfr will also have published load tables which you can justify your design...

That is a darned good idea. You also get a higher ceiling on one side of the space. Always an advantage.