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Thread: Questions on truss spacing and roof design

  1. #16
    Quote Originally Posted by John K Jordan View Post
    Yes, I’d sit down with the truss manufacturer for recommendations. On my shop I used 4’ spacing, 2x4 purlins, a layer of OSB sheathing, and felt underlayment with metal roofing on top. I chose 5v galvalume roofing in a heavy gauge (I forget what) with a good ridge vent, of course. Lots of bracing inside. My building was only 62’ long. I built with 6x6 posts every 10’ around the perimeter with double 2x12 beams, (several posts in the center inside interior walls, 2x6 studs on 16” centers, 2x4 girts, with smartsiding over OSB, 1/2” ply on interior walls. BTW, most trusses I’ve seen were 2x4. I opted for 2x6 top and bottom chords and 2x4 web. The whole building is very solid. The biggest effort was setting the 16’ 6x6 posts and putting up the beams. (I got someone to help with that.)

    I’ve seen barns put up with 10’ between heavy trusses. I thing they used 2x6 perlins.

    I’m planning to put up a 24’ or 30’x76’ equipment shed soon. Probably go with 8x8 posts and same roof construction. However, I’ll go with steel trusses on this one. They have built-in channels to hold 2x6 perlins; those I want to use provide a lot of interior height down the center of the building - nice for excavator, etc.

    There are lots of books on building design and I found a lot of recommendations on the internet. Again, whenever I’ve ordered trusses the truss designer provided options and details.

    JKJ
    John I am curious, how do metal trusses like this compare price and strength wise to a typical wood truss? I would probably be able to get by with an 8ft to 10ft spacing with metal trusses and the purlins like you mentioned. If I build it 180ft x 40ft then I could use two 20ft beam style trusses times 18 all the way down. How would you compare the two?

  2. #17
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    Quote Originally Posted by Bobby Robbinett View Post
    John I am curious, how do metal trusses like this compare price and strength wise to a typical wood truss? I would probably be able to get by with an 8ft to 10ft spacing with metal trusses and the purlins like you mentioned. If I build it 180ft x 40ft then I could use two 20ft beam style trusses times 18 all the way down. How would you compare the two?
    I don't know, never used them before. They are much smaller than the wood trusses. What got me interested was a guy down the hill who had a big equipment shed put up a couple of years ago. Someone he found recommended steel trusses and built the whole thing in way less time and for less cost than he imagined. (looks like he put them about 8' apart) The guy said they hauled them in from out of state somewhere. I don't know about the availability of the steel trusses now.

    One web site I looked at said the steel trusses are more expensive but you typically need 5 times more wood trusses. https://www.americanpolebarns.com/po...e-a-no-brainer

  3. #18
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    OP you might benefit from watching some RR Buildings YouTubes and/or Texas Barndominiums youtubes, although the latter hasn't posted anything in several months.

  4. #19
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    Quote Originally Posted by Lawrence Duckworth View Post
    for how long? My son had that crap sprayed in when he built his house (8,500 sq ft) . When he remodeled a few years later and opened up an exterior wall and found the stuff had shrunk away from the studs and osb.
    That sounds like a defective installation. If you've ever had to physically remove the stuff, you'll have found it really takes a lot of effort and at the junction between the foam and the structure, you literally have to cut it away with a blade.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #20
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    Quote Originally Posted by Eugene Dixon View Post
    OP you might benefit from watching some RR Buildings YouTubes and/or Texas Barndominiums youtubes, although the latter hasn't posted anything in several months.
    Yea, RR is the bee's knees when it comes to post frame structures...few builders go as far as Kyle and Greg go when it comes to straight and square for the same, too.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #21
    Got a quote from a guy in Louisiana on using steel trusses. He said I would need 19 of them, and they are 20ft long each that bolt together in the center for a 40ft span. They are going to run roughly $700 each x 19. Which is cheaper than wood trusses using a 4ft spacing on center per the Manards website. I need to contact some local truss companies and get some quotes. I built a couple of triplexes a couple of years ago and got the trusses locally at $185 each. Can’t recall the span or number that I used, but I am guessing they would be significantly cheaper than Manards.

    I would of course much prefer to not have to sheeth the roof. That would save me a ton of money and since I am paying for this out of pocket and not getting a loan I need to save money where I can. I have a local company to get the metal roofing panels from that run $3.59 per foot with up to 55ft lengths. They might be able to get that price down even lower according to their salesman.

    We don’t get much if any snow. We do get a lot of strong wind and rain though.

  7. #22
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    Quote Originally Posted by Bobby Robbinett View Post
    ...

    I would of course much prefer to not have to sheeth the roof. That would save me a ton of money and since I am paying for this out of pocket and not getting a loan I need to save money where I can....
    Some sort of insulation would be needed to prevent condensation in many areas. I've seen several metal-roofed buildings where moisture condensed on the underside and dripped into the building. Some recommend a bubble plastic insulation just under the metal roofing. A spray on foam should work. I used the OSB sheathing under the metal and synthetic roofing felt to help manage the condensation, for the strength when walking on the roof, and to add to the overall rigidity of the structure. For areas open under the roof I painted the bottom side of the OSB.

    JKJ
    Last edited by John K Jordan; 06-29-2022 at 8:42 AM.

  8. #23
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    The bot-together metal trusses are a viable option and worthy of comparison. You mention wind and with your reference to Louisiana...I'm making an assumption here since you actual general location isn't displayed...makes for the importance of proper engineering for wind. Structures are stressed with different kinds of loads in different geographies and wind really has to be dealt with. It's ok to try and mitigate cost as much as possible, but one place you can't afford to cut corners is ensuring that that building remains standing over the years through heavy weather.
    --

    The most expensive tool is the one you buy "cheaply" and often...

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