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Design help with framing a gothic arch greenhouse in snow country

Design help with framing a gothic arch greenhouse in snow country

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  #1  
Old 03-16-14, 12:27 AM
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Design help with framing a gothic arch greenhouse in snow country

I am framing a gothic arch greenhouse in snow country (plans below). The main structure consists of 4x4 beams with 2x8 purlins and 2x6 rafters trussed with a 2x8 cross member. All are set 4' on center.

In addition, I will bend and glue laminate clear poplar to form 2x4 arched bows (spaced 4' on center) which will anchor to 4x4's (attached to concrete piers) and also tie into the 2x8 purlin via Simpson strong ties.

Not shown in the drawing are 2x4's horizontal bracing between the bows and rafters (every 2'). The greenhouse material is 5mm Solexx.

Strength Questions:
Can you advise whether this design is likely to support a 3 feet snow load (40 psf)? Due to design, cost, and effort to laminate, I need to keep the poplar bows to 2x4's. However, due to their steep slope, I don't expect that part of the greenhouse will have significant snow build-up.

I have enough experience to be dangerous, but I have not attempted something as unusual as this.
 
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Last edited by mseifert; 03-16-14 at 02:22 AM.
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  #2  
Old 03-16-14, 03:54 AM
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I would think it could handle a snow load on the top portion, and anything on the curve may not be crucial due to the design. My question is what type windows/glass are you installing, and where? It seems most of your glassable area is curved, and I wouldn't think you would want curved glass.
 
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Old 03-16-14, 10:58 AM
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"what type windows/glass are you installing, and where?"

I am using Solexx 5mm rolls. They will roll / cover from bottom to top to bottom in one 30' x 4' sheet without any seams. It is flexible enough to bend over the arch peak yet should be strong enough to support snow load. R-value is 2.3. The bottom two feet on either side is vertical and will be framed (between the 4x4's) with a set of windows that run the length of the greenhouse for cross ventilation.
 
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Old 03-16-14, 11:03 AM
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Detail on the framing

Attached is my concept of how the post, purlin, and joist will meet. I would appreciate comments on this.
 
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Last edited by mseifert; 03-16-14 at 11:28 AM.
  #5  
Old 07-19-14, 11:21 PM
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Design help with framing a gothic arch greenhouse in snow country

Its funny - I was looking for plans for how to build one of these things and came across this thread. I did not take the trouble to check the date of posting and so went through the registration process - I now realise this was posted in 2005 and therefore most unlikely that the originator will read this!! Anyway - I located the original Mississippi University plan (6298) on this design and I cannot understand the reason for the author of this thread choosing to add lateral rafters. The whole idea is that the strength lies in the geometry of the gothic rafters and thus there is no need for bracing across the centre. Final comment; if 5mm twinwall polycarbonate is used and properly pinned to each rafter then it will, in my humble opinion, hold well. Hopefully this will help subsequent builders (after 2005)!! Regards to all
 
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