Exposed fasteners versus hidden for metal roof

[reader2580]

As I said above .. read the specification of the exposed fastener roofs. They leak and need a base -- you still cant use them if a building requires a "roof".

I'm confused on why exposed fastener panels would not be considered a roof?

I have already made the decision to put a plywood substrate on the roof when I build my building. I will almost certainly use hidden fastener metal if I do metal.

 

[yeldogt]

I'm confused on why exposed fastener panels would not be considered a roof?

I have already made the decision to put a plywood substrate on the roof when I build my building. I will almost certainly use hidden fastener metal if I do metal.

Because they leak ...

If you go online and download instructions and specification -- some get into the weeds.

A "roof" is not supposed to leak.

I have a good friend who reps metal roofing -- you can't specify exposed fasteners for any kind of job that's got specifications that call for a waterproof system. Basically -- the roof protects the base sheet. The best you can do is go with a good base sheet that is somewhat self sealing and hope any drips fall on a fastener that's also sealed by the base sheet.


If you look at my roof above .. that's basically acting as both a base sheet and a slip sheet .. they use large head nails. It would be suitable as a sealing membrane.

I my case I had to fully cover the roof to avoid moisture migration from the building -- and the back of the panel is plastic coated .... that's Zinc specific. With a metal roof .. you have to understand what's going on.

 

[Farmall450]

One thing I didn't realize is the majority of the hidden fastener panels require a substrate and can't be put over open framing. I was planning on open framing.

90 sheets of OSB or plywood is not a small cost plus the labor for installation.

^^^^^
I don't think many people looking into this do

 

[bradpac]

Put a 2" standing seam on it, open framing. No plywood. Spend the money for plywood on spray foam and coat the underside of that sucker when you're done.

 

[MrSurly]

I briefly considered standing seam for my Texas build (the 2" tall stuff) and I was willing to consider the extra three grand in metal.... but then the guy added the "oh by the way... you'll need to sheath it in plywood". This was bad in more than one way; There's the extra cost for the plywood of course but there's also having to
re-submit to the engineering firm for new drawings
send the new engineered drawings for permitting again
buy different, more expensive trusses due to the change in loading...
it got carried away really quickly.
I assembled with 26 ga open fasteners on the flats on #2 SYP kiln-dried purlins.
Spray foamed underside straight to the metal,
For around five grand premium for the standing seam, I decided to just buy some extra screws.

 

[jkeyser14]

Put a 2" standing seam on it, open framing. No plywood. Spend the money for plywood on spray foam and coat the underside of that sucker when you're done.

You can't. The clips need to go onto sheating and the sheating helps keep the panel from bending between rafters and opening up the seam.

 

[JamesW84]

I was 100% against an exposed fastener roof also. I wanted to shingle it because I was comfortable with that. The truss manufacturer said I would need trusses 2 ft O.C. if I sheeted it for shingles, so that would double my truss cost ($3000) + the cost of the plywood ($1500).

I was looking into the snap lok (central states preferably, but others also IIRC). It was going to be $250/sq for snap lok vs $85 sq for panel loc plus (My roof is 32 sq = $5200 more for snap lok + sheathing ($1500) + extra trusses ($3000) = $9700 more for standing seam vs exposed fastener (In my case).

I ended up going with 26 gauge central states panel loc plus and using screws with EPDM washers instead of neoprene. I was also very careful to install the screws with the correct compression on the washer. My roof has roughly 2500 screws. I missed on some, so I went back underneath and sistered in some more purlins to give the screw something to bite into. I would not put caulk over a hole.