# maximum simple 2x4 truss span



## fulton 22175 (Mar 16, 2011)

ok number 1 the osb or plywood you want to use is way to thin especaily in the mountains , use 1/2 osb or plywood , do you now how much a square of shingles weigh average 220pounds per square , i see disaster ahead if you plan to do this the way you want to


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## Bud Cline (Mar 12, 2006)

"Reasonable snow load?"

What's the actual anticipated snow-load?
Or annual average snowfall in that area?
Is 4:12 suitable there?


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## mrroofer (Aug 24, 2011)

Fair enough.

3/8 or 7/16 has been the predominant thickness of roof sheathing here for as long as I have been in the trades, which is about 20 years. I know there wont be an issue there.

I think OSB is made differently here in Canada, or something...

A bit more thought into the situation has led me to concur with the disaster statement.

With regard to snow load, the location is about 10 km from the nearest measurable centre at 150 cms.

I also dug this information up from jabacus.com;

*<H3>Specified Snow Load *

S = Is[Ss(CbCwCsCa)+Sr] [4.1.6.2] 

*Factors *

Location: Calgary, Alberta
Ss = 1.1 kPa / Sr = 0.1 kPa 
Importance Factor, ULS: Is = 1.15 / SLS: Is = 0.9 
Roof slope = 26.6 degrees 
Slope Factor 
For non-slippery roof: 
Slope <= 30 degrees. 
Cs = 1


*ULS: *

*S = 1.15[1.1(0.8*1.0*1*1.0)+0.1] = 1.13kPa *

*S = 1.13 kPa *

*S = 23.5 psf*



*SLS: *

*S = 0.9[1.1(0.8*1.0*1*1.0)+0.1] = 0.88kPa *

*S = 0.88 kPa *

*S = 18.4 psf*





</H3>

I do not know how to interpret these figures however :huh:.

The snow load here I have discovered to be surprisingly light compared to many places not so close to the mountains, specifically eastern Canada.

Looking into things more I think it might be best to construct either a Kingpost or a Howe set of trusses at a 6 or 7/12 pitch (as suggested by the info above)

If the trailer needs to come out there is always the chainsaw... 

There are actually a lot of 4/12 shingled structures in the area. The biggest concern as far as loads go would be trees snapping off in a wind storm. There are lots of tall spindly black poplars around which tend to snap off about halfway.


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## fulton 22175 (Mar 16, 2011)

Your from CANADA that explains everything ! LOL just kidding friend, alot of OSB is made in CANADA almost all of it as far as i now , if it were me i would go with 1/2" osb with H-CLIPS it would make for a more secure roof


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## mrgins (Jan 19, 2009)

fulton 22175 said:


> Your from CANADA that explains everything !


LOL
I agree with what fulton says, although I still prefer 5/8" cdx in snow country


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