Wall of Windows
Wall of Windows
(OP)
I've got a wall of windows on a gable end with possibly two methods of framing it (so far). Can anyone tell me what is wrong with the first picture? Note that 22 ft. of roof is tributary to to the glulam beam at the ridge (actually only half of that 11 ft is tributary to the gable wall). The load is the S + D, the dead load is approximately 50% of the total load.










RE: Wall of Windows
I much prefer the second option with the two full height columns taken to the roof diaphragm.
Mike McCann, PE, SE (WA)
RE: Wall of Windows
Have I passed the quiz?
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Wall of Windows
With the 189 plf load on the glulam beam in its weak direction, neglecting any straps that may counteract this lateral load, even sistered with two 2x6 (top and bottom) I get the following:
fb = 4500 psi > Fby' = 2530 psi (CSI = 1.78) ======> NG
Also if the beam doesn't snap it will deflect 15.2 inches. Granted the wall may act as a web to some degree and resist this lateral deflection but I wouldn't count on it.
Then you take the vertical loads which will only make matters worse (hinging effect).
Hence Rev. 2 of the design... and I need to explain to the architect/designer why his wall of windows won't work.
RE: Wall of Windows
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Wall of Windows
The load coming out of both ends of the Glulam would be in the range of 4,000+ lbf - not your average wind load.
A quick glance at your Second drawing (much better design in my opinion) gives me concern about the 2x12 rafters.
Tall gable end walls always need special concern for the lateral support at the roof decking.
I would frame the wall full height to the roof decking and attach a 2x4 or 2x6 ladder spanning at least 24" (your first roof truss / rafter past the wall), possibly 48" depending)
The Ladder framing runs at 12" OC. perpendicular to the wall with:
-nails to the roof decking to transfer lateral load to the diaphragm
-nails to the double top plates to transfer load to the ladder framing
-this allows you to cant out for overhang as well
See the attachment for a similar design I have done - pay attention to the lower right hand for the ladder framing detail
RE: Wall of Windows
How about something like this:
If more strength is needed put another 2x4 block in line with the outlooker to the next rafter (and strap tying the two together).
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Mike McCann, PE, SE (WA)
RE: Wall of Windows
I think it's unlikely that you need the capacity of a 6x6 over a short height like that.
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I usually just call it a cripple post / cripple stud (same as I call the studs below sills)
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off topic question: where abouts in the world are you, and what is the 'standard' lumber species you use. I see a lot of D.Fir being used, but where I am if you spec anything other than SPF you get a lot of angry calls
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Those are pretty extensive calcs and sketches. How are you making any money on these jobs?
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The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
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If you go to the internet and type in "ilevel residential wall guide" that will take you to Weyerhaeuser's specifier's guide to walls that you have shown in your sketches and drawings. The guide has a lot of typical details that might help you in your design.
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As the youngins would say, 'Mad props, yo'
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Not often, but on occasion I have seen the contractor install hangers that did not have the published capacity required. One guy tried to use fence brackets.
Would it have ever been a problem? Unlikely, but I'm not one to argue with the published capacities.
RE: Wall of Windows
How does the LVL receive lateral loads if the roof diaphragm uses the LVL as a chord or drag strut? Or use the whole roof as a diaphragm and strap the rafters to each other over the ridge.
Can you use balloon framing 6x6 post between the windows and use connectors to the roof boundary members.This eliminates the continuous header. You can use 2x6 plates in the strength plane as headers. For extra strength you can use buckets and blocking at the post bottoms. Since the end SWS carry the lateral loads the 6x6's are carrying gravity and wind force perpendicular to the wall,