Recently ran across a steel roof on a two year old house. The roof trusses had been strapped and the steel roof was applied to them. There was no roof deck beneath the steel roof material. Is this ‘kosher’?
No. How would you screw the roof down? Hope to hit the truss every time?
HI NICK
NO, The roofing is screwed to the strapping which in turn is attached to the roof trusses. So, when viewed from inside the attic you see the bottom of the steel roofing and the bottom of the strapping to which it is attached.
Many thanks to Mon Cher Marcel Gratton who is much better at googling than I am. I had barely posted when Marcel sent me the answer with illustrations ! Merci !
Could be ok??? But probably not! Depends on the manufactures specs…. This is no deferent that a cement tile roof installed on skip sheeting like back in the old days. In today’s world there should be a solid deck with felt but you never know! Write it up!
What does that mean?
And what did the illustrations depict?
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Garages and barns are built this way, but the strapping is actually 2x4s or 2x6s that are considered framing, over rafters or trusses 24" on center.
The strapping is in effect a roof purl in. Perfectly appropriate if it is sized sufficiently for the roof loading. Depending on the spacing it could be described as skip sheathing. Also common under metal roof around here.
It all boils don to the roof truss MFG installation guidelines. The installation of roof sheathing may be required for the strength of the roof system.
Also, the metal roof MFG warranty comes into play, here in the NE I would like to see a moisture barrier under that roof.
I am with Peter, I would be a little skeptical installing any type of metal roofing on strapping furring unless it is a shed, barn, or chicken farm building.
On a house, it is a fact that it can be installed on skip sheathing, but that is different than furring say every 16" spacing.
Even the cheap corrugated metal I have installed on chicken barns a long time ago were 2x4’s at 16" o.c., which provided the lateral stability of the trusses somewhere close to a full sheathing of the roof.
Pictures would be helpful, but then maybe Marcel Gratton knows more of what Vern is talking about.
Check out this link where this was mentioned;
http://www.nrca.net/consumer/types/panel.aspx
Roof deck
Architectural metal panel roof systems and structural metal panel roof systems are installed over a large variety of substrates. There are two general categories of substrates: continuous or closely spaced decking that provides solid support for the metal roof panel, and the other is composed of spaced structural supports (such as purlins) where the metal panels must span between supports. Most structural metal panels are used over spaced structural supports without being supported by a solid roof deck.
Metal shingles and metal shingle panels should be installed over continuous or closely spaced wood decking, furring strips, or metal or wood purlins using a batten or counter-batten system. These roof coverings typically are considered to be watershedding roof systems, so the roof slope should be 3:12 (14 degrees) or greater.
:)
you guys need to come out here to CA we have roofs installed over skips allover and waht sucks the local building dept. ALLOWED This chet to go on! Now let me put my roofing contractors hat on…this all comes back to the manufactures specs…if they say ok them it goes! This does not mean I will install it that way but I would like to see pics of this roof to know what kind of metal we are dealing with…then we can say ya or na onit…my 2 cents!
I agree Brian. I would not be the first one to recommend strapping on a house to install a metal roof.
I have know idea if we are talking about a standing seam metal roof or the cheap corrugated metal that people have been installing on failed roof shingles over here to save money. And when I say cheap, it is cheap that you would install on the hen house. :mrgreen:
We have wind, snow, condesation, poor ventilation, ice dams, and everything else in the book up here to think about.
Sheathing, waterproof underlayment, and go, is the only loggical way.
Manufactures recommendation is the best protection for their product design. Especially if you want to inforce warranty when something goes wrong. 
do you think that would not sag with a foot of snow on it some times two feet with drifts