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metal roof attachment on new construction

SCBO1

SCBO1

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Not sure if this meets the IRC code or not.

Q. Can metal roofing be attached to 2x4 cleats (sometimes called purlins) on 24-inch centers? The cleats go across the roof trusses. Is the metal required to be attached to roof sheeting?

Plans call for a reflective vapor barrier below the metal.
 
If the IRC does not have specific provisions for metal roofing then I suggest that the applicable code is the IBC.
 
R905.10 Metal roof panels.
The installation of metal roof panels shall comply with the provisions of this section.
R905.10.1 Deck requirements.
Metal roof panel roof coverings shall be applied to solid or spaced sheathing, except where the roof covering is specifically designed to be applied to spaced supports.

In other words manufactures installation instructions
 
cda said:
Maybe let the owner know it may leak??
Click to expand...

The owner is the builder, a metal barn builder, and this will be his home, he sez. Eventually they become someone else's home or nightmare.

mtlog, I'm with you, I found that nugget of information when doing the review. The manufactures install instructions allow for spaced supports. (Terms used: nailer's, purlins, cleats) not to exceed 24-inch o/c. The engineer the looked over the plans didn't make any hub about it either.

Water and condensation will get it eventually I predict.

So far the plans meet R905.10.1 spaced supports (2x4's) over trusses
and R905.10.2 (1) (5/12-pitch roof)
 
Forgot to include
R905.10.5 Underlayment.
Underlayment shall comply with Section R905.1.1.

not sure how to comply with the code using space supports

R905.1.1 Underlayment.
Underlayment for asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles, wood shakes, metal roof panels and photovoltaic shingles shall conform to the applicable standards listed in this chapter. Underlayment materials required to comply with ASTM D226, D1970, D4869 and D6757 shall bear a label indicating compliance to the standard designation and, if applicable, type classification indicated in Table R905.1.1(1). Underlayment shall be applied in accordance with Table R905.1.1(2). Underlayment shall be attached in accordance with Table R905.1.1(3).
 
Manufactures written installation instructions always win over the code

IBC 2015
1507.1 Scope. Roof coverings shall be applied in accordance
with the applicable provisions of this section and the manufacturer’s
installation instructions.

IRC 2015
R903.1 General. Roof decks shall be covered with approved
roof coverings secured to the building or structure in accordance
with the provisions of this chapter. Roof assemblies shall
be designed and installed in accordance with this code and the
approved manufacturer’s instructions such that the roof assembly
shall serve to protect the building or structure.
 
Pcinspector1 said:
Not sure if this meets the IRC code or not.

Q. Can metal roofing be attached to 2x4 cleats (sometimes called purlins) on 24-inch centers? The cleats go across the roof trusses. Is the metal required to be attached to roof sheeting?

Plans call for a reflective vapor barrier below the metal.
Click to expand...

Yes absolutely you can attach the roofing.
 
I would not allow glue only for the furring stripes. The stripes need to be properly fastened to the roof structure (rafters, trusses). The use of glue/adhesive between fasteners would most likely be okay.
 
As mtlogcabin provided, it is all dependant on the manufactures installation instructions/specs. Attaching to spaced purlins is usually a commercial design but not always. This arrangement precludes the installation of the lighter gages of roof panels, when it is allowed.
 
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