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Discussion Starter · #1 ·
In the pic attached, standing seam panels are apparently installed over purlins, instead of directly atop the papered or membraned roof.

This roof is done with SIP panels, and the top surface of the SIP is 7/16" OSB.

So, what happens usually?

I'll not use the SIP, but will likely use OSB, maybe Huber's Zip-wall coated product.

Rafters will be 24" on center. What is the preferred thickness of the sheathing for the deck? Must the roof be strapped with purlins, as shown in the pic? If so, what is the makeup of the purlins?

Wood? Rollformed steel hat sections?
 

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There are some standing seam profiles that can be installed over top of purlins. That being said I don't think it's a good idea.

Standing seam especially mechanical lock does best over a solid substrate or at least skip sheathing.

Two layers of 15 pound felt is best, one layer of 30 pound felt minimum. There are synthetics out there but I've not been totally pleased with any that I found yet.

24 gauge is preferred and nominally more expensive than 28 or 26.

My 2 c

Mike
 

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It depends in what type of panel profile they are. There are 2 types of panels, architectural panels & structural panels. Most of the time if the rib of the panel is over 1.5" it is consider structural. If it's 1.5"or under it is Architectural. Structural can be installed over purlins and Arch. Are to be installed over a solid deck. Generally 7/16" to 5/8" is what we install our panels over. We will use ice/water over the entire area to dry it in or sometimes use a synthetic if we need to cut down on cost and ice/water only where it's needed.
 

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I always use 5/8" OSB and 30 pound felt in IL.The only time we use purlins is with structural 1.5 rib on pole buildings.
 

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Discussion Starter · #7 ·
7/16 on a roof? Why sure, not just in TX, but in vast areas in the lower 48. Vast areas.

Checked the manufacturer's spec (Berridge) and they say OK right on deck, it needs to be 5/8" minimum, and over it, two, not one, layers of 30# felt.

And try to find real 30# felt. What is sold today is phony, and the make it seem OK by putting the # sign on the other side of the 30.

Thanks for the replies.
 

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Nothing less than 1/2 on any of my builds. For our house I used 5/8 for a lower roof and 3/4 for the main roof.

I've used it on some jobs, but most customers don't want to pay the extra however.

As to the felt you must specify astm 30, a little more money but definitely worth it.

Mike
 

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Only 7/16" glued to ISO Board over a metal deck, sorry didn't mean all by its self. 5/8" over rafters. A lot of builders around here are installing a metal deck then installing7/16" OSB glued to and ISO Board then will install metal roof over it.

2 layers of felt?

What manufacturer specs 2 layers?

We only use 24 gauge coil we buy from Englert and PAC - CLAD and neither of them have that in there specs, but there are on every corner now days anyway so I wouldn't be surprised if some did.
 

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Discussion Starter · #10 ·
ASTM D-4869 #30 felt, roofing-spec felt, must be what we're talking about.

Two layers, it's right there in Berridge's spec, best achieved by half-lapping the strips. It's why one of those dashed alignment lines is right down the middle, I guess.

Thanks again for the insights.
 

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In the pic attached,

Must the roof be strapped with purlins, as shown in the pic? If so, what is the makeup of the purlins?

Wood? Rollformed steel hat sections?
The picture you posted is what you want to avoid. If you strap your roof , run your battens on a slant to allow the roof to breathe and any moisture to escape.

1x wood material is fine.
 

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What Berridge panel spec's 2 layers of 30? The cee locs only spec one. If they spec two I'm guessing because of the slope. Under 2-3:12 maybe?
 
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