Truss spacing on building quotes

[Oldmaple]

I have 2 quotes I am considering on a 40x40 (or longer) pole building. The truss span will be the 40' width with 4/12 pitch. One contractor is spacing the trusses 2' centers, osb on that, then metal roofing (sounds similar to home roofs). The other contractor is spacing them 4' centers with metal roofing. I have another pole building with trusses at 4' and haven't had any problems with snow or wind but it is only a 24' span. I assume that they would both meet code. Prices are within $1,000. Any opinions?

 

[rburke65]

Wow....... Well for the difference of 10 hundred dollars there should not even be a question. Good luck.

 

[Nekit]

Either would work, but for the small cost I would go with the 2' and sheeting. It's more than needed, but should hold up better too.

 

[Nekit]

Just noticed you are in W. Michigan. If you get much lake effect snow the stronger setup might be a nice piece of mind too.

 

[Sureshot]

The bigger the span the heavier the truss. Mine were 6', lots are 8'. Around here commercial buildings are 4'. The ones I have seen are generally spaced the same as the poles. If someone goes 4', 6' or 8' spacing on the poles the poles are also sized accordingly.

 

[83c10submariner]

2' for sure!!! If you ever have to get up on the roof for a repair or something at least falling through a 2'oc you have a chance of catching yourself. Also the extra support for snow load and ice. People seem to forget about the ice. Going with what commerical building do is not always the best. A mall roof clapsed in Ontario a couple winters ago. Also look up the Montreal ice storm. Also most products are made for 2'oc ie. lighting supports and chimney bracing. So it might also save you some headaches further down the road.

 

[larry_g]

Without knowing the engineering specs on the trusses and the other construction details of the building and roofing system then the information your getting here is no more than a guess by the poster.

lg
no neat sig line

 

[s_ontario]

Have your contractor price out 6/12 trusses mine where $18.00 a piece less then 4/12 and since house was 6/12 matches the look and snow slides right off

 

[finn]

Ask both contractors what the design load for their roof construction proposal is.

Logically, my first impulse is to select the closer spacing and osb, but thinking about it, the osb adds to the dead load and not all truss designs are equal.
Number of trusses an spacing are only part of the equation.

 

[bczygan]

A couple of factors.

The 2' spacing allows for easy attachment of ceiling and insulation to bottom chord of trusses. 4' is more problematic.

The statement above about load bearing capabilities of each alternative is very important to check. Not just the wind and snow load capabilities, but the bottom chord of truss dead loads. This will tell you what you can hang from them or what you can put in the attic space.

I would also go with a steeper pitch and consider beefing up the trusses to make storage in the attic space. You may be limited on height by zoning, but a narrower and longer building can help with this. That also helps by reducing truss spans and cutting their costs. I never design a square building, but use the "Golden mean" for the length to width proportions. Will 32x50 work on your lot?

Bill

 

[boiler7904]

Make sure they both meet local wind, uplift, live, and dead load requirements for your area and put that in the quote.

I'd prefer 2' on center with osb sheathing if money is basically the same.

As previously mentioned, steeper pitch will shed snow better.

 

[G McKay]

The metal buildings you see have steel 4"X4" studs and rafters. They are 5' apart. They will hold up to 3 feet of snow. If the steel roofing is placed ACROSS the roof, you aren't going to fall through if you have to go up on the roof with only metal on the roof. The only problem with the roofing running across the building is that it is harder for the rain to run off of it. But it is stronger than if it is run up and down.

So, if your roof has 4 feet centered trusses, it should easily hold you up without the sheathing. There isn't going to be that much difference in the two as far as strength.

The only problem you might have is: without the sheathing, the roof may sweat if it gets air tight or if you have heat.

 

[danfromsyr]

never let engineers/builders offer up minimum code specs..
sure minimum specs are deemed safe and satisfactory.. but who wants just that..
it's quite cheap to add a bit of overkill into roofing/framing/foundation/slab compared to if the minimum is ever not enough..

 

[nfk]

IF its an apple-apple comparison I would pick the 24" centers. Are the trusses the same other than spacing?

 

[yeldogt]

IF its an apple-apple comparison I would pick the 24" centers. Are the trusses the same other than spacing?

Not a pole building .. When I did mine the wide spaced truss configuration used massive trusses that were much more expensive. I liked the more open look.

 

[Oldmaple]

Thanks for the input. I don't have the specs for the trusses. I assumed that the 4' center ones would be beefier since there wouldn't be as many. Both contractors are longtime, reputable, and local so they both should meet code. I do like the osb for sound deadening. I am not planning on finishing off the inside, just maybe hanging a deer or 2 if I'm lucky.

 

[Sureshot]

You better have fall protection if on that metal roof. Mine was 3.5/12 and even a little sprinkle made it very slippery. I had another that was 4/12 and was tough to walk on.