Metal Roof Diaphragm 2

[JStructsteel]

Looking to use a metal roof diaphragm...26 gauge. Looking at the ESR report, it has span, and then number of spans.

I am assuming that the span is the span between the nailers, and number of spans is just that, number of spans per sheet?

My architect has the nailers at 2' o.c., 4' truss spans. Design those and let that dictate the spacing/span?

 

[dik]

The Steel Deck Institute has an excellent publication Steel Deck Diaphragm Design Manual on using roof decks as diaphragms. You might want to dig up a copy.


-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JStructsteel]

Dik, I should clarify this is using the metal roofing as the diaphragm over wood.

 

[structSU10]

I think it may be appropriate. My first look however would be to see fastener capacity into the wood vs. into steel if the ESR is based around steel support. I would guess the slip potential in the wood, or lesser fastener capacity, would affect the diaphragm capacity and stiffness in some way.

 

[dik]

Not recently, but I've used Hilti metal fasteners with PSL material... based on CSA S136 CFS code values for shear considering the load is so close to the lumber that the deck and fasteners are loaded in shear only. I then had to convince myself that the PSL could take the loading. Wasn't too difficult....

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[ZXLeung]

Typically, we run with the online calcs via the link below for roof deck diaphragm check:

Link

 

[hokie66]

Using roofing as bracing defeats the purpose of the roofing, which is to shed water. Steel roofing should be either standing seam which is connected with sliding clips, or other profile screwed through the crowns, not the valleys.

 

[dik]

For pre-finished metal roofing, with standing seams, generally... most metal deck has a waterproof membrane applied over and the fastening generally occurs in the 'valleys'.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[hokie66]

The application of a membrane over metal roofing would be a new one on me. Metal roofing is intended to shed water on its own, if installed at enough slope, which depends on the profile. Now if you are talking about metal deck, that is a different animal all together.

 

[XR250]

This is pretty common in residential and barn construction (at least in my area of the States)

 

[JStructsteel]

The shear load is low, 150plf. Im using published guidelines from a manufacture, I assume they have the water details worked out.

 

[XR250]

screwed through the crowns, not the valleys.

This has been and always will be debated by roofers.

 

[hokie66]

The thing with metal roofing in the United States is that it is not the roofing system of choice in either residential or commercial buildings. You use those shingle things on houses which need to be replaced every 20 years, and built up flat roofing systems on commercial buildings, which also have lots of maintenance issues. So you really don't have a track record of metal roofing. Barns, fine, it doesn't matter so much if they leak. But if you are serious about metal roofing for large structures or for houses, there need to be better standards developed or used. And those standards should not consider that the roofing provides diaphragm bracing, IMHO.

https://www.lysaght.com/sites/default/files/LysaghtRoofingWallingInstallationManualJul2015.pdf

 

[slickdeals]

An excellent document is this

https://vercodeck.com/wp-content/uploads/2021/04/Roof_Deck_Design_Guide_V2021.pdf

 

[hokie66]

slickdeals,
Yes, that is a good reference. But it is about steel deck, not steel roofing.

 

[driftLimiter]

What is the profile of the roofing your aiming to use? & Does the manufacturer provide diaphragm strength and flexibility values?

Generally if its less than 1.5" deep I have had to use horizontal bracing because it doesn't have diaphragm values.

 

[JStructsteel]

I was looking a panel that was 1.25" deep and had published values. Arch told me the contractor bid a panel with 3/4" deep ribs. So not sure if they have values for that.

 

[hokie66]

For roofing, the architect should specify and verify that the profile is installed on a roof of appropriate slope and slope length.