Thread: Metal Roof Installed on 1x4s

I've always have seen metal roofs installed onto a roof decking system with an underlayment. Is it acceptable to install a metal roof onto 1x4 slats?

thanks,

brian

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How old is the structure? Are the 1x4's spaced out? Depending on the age this could have been an acceptable method of roofing at the time.

the home's age is 1989....spacing is about 4 feet on center.

What type of metal roof were you looking at?

It really depends on the type of roof when it comes to the sheathing or decking. Skip sheathing is very common with metal roofs.

I could not upload the file that I have attached the link for. It should tell you what you are looking for. http://www.fabral.com/downloads/details-postframe.pdf

Most corrugated panels can be installed on the skip sheathing, but all (as far as I know) standing seam roofs must have solid sheathing. As Scott said it all depends...but the 4' spacing seems a bit much.

That is how the tin often gets put on homes up here on acerages and farms.

Some contractors feel that 7/16" OSB roof decking is a poor choice for the supplied screws, preferring the "solid 1X4's". The 1x4's are usually applied right over the shingles once the sheeting and shingles overhangs are cut-off. Better contractors screw the 1X4's to the joists, others simply used framing nailers and straight nails.

Never seen or heard of anyone using any underlayment, until they built the community hall. The architect spec'd horizontal 1X4 strapping over the sheathing, and then #15 roofing paper over that, somehow thinking that the paper wouldn't sag between the strapping and cause "damming", not to mention the logistics of trying to hold down all the paper while bringing tin onto the roof without making holes in the paper

Eventually, he consented to having the strapping placed over the paper provided 1/2 rabbet/saw kerfs were created on the bottom of the straps to create weep/drain holes.

Depends on the metal roofing.

Most you see on homes and many commercial building is non-structural metal roofing and needs to be on solid sheathing.

On metal frame building and the like you will likely see structural metal roofing installed on purlins (that is what those 1x4 are - purlins) and THOSE metal roofing panels are rated for that type of installation.

Installing non-structural metal roofing on purlins will allow the panels to flex, bend, crimp, and otherwise become damaged in some way, which is why they are "non-structural" metal roofing panel and need to be installed on "structural" solid sheathing.

From Pro Panel's web site:

Pro-Panel II is designed to be utilized over open structural framing, but can easily be used with a solid substrate.
The recommended substrate is 5/8" plywood with a 30 pound felt moisture barrier. To avoid panel distortion, use
a properly aligned and uniform substructure.

I have it installed on my house on 2x4's spaced every 24". I wouldn't recommend it, because you have to be careful where you step or you can kink it pretty easily. Other than that it's been almost 20 years on a low slope application (1.5:12), and we've had no problems other than at the skylight, which is not unusual.

From Westform Metals' website
"We recommend prolok be installed over solid substrate, installation over strapping is possible."


From the Canadian Sheet Steel Building Institute

"Is it necessary to strap the roof first before installing the steel roofing? Not always. Some roofing manufacturers require strapping to fasten down their products, so they should be consulted. In a re-roofing application strapping can be useful to provide better anchorage to the roof trusses and to level out the roof surface. There is also some advantage to having an air space behind the roofing, but not all manufacturers insist on it. Consult the manufacturer."




Hope those links help ya!

Thanks,

Based on Jim's pdf, the house has 5v crimp and requires the 5v on roof decking not slats....here's the picture; do you agree its 5v crimp?

brian

Originally Posted by brianmiller

Thanks,

Based on Jim's pdf, the house has 5v crimp and requires the 5v on roof decking not slats....here's the picture; do you agree its 5v crimp?

brian

Yep if it is 5V then it needs to be on solid decking.

Originally Posted by brianmiller

Thanks,

Based on Jim's pdf, the house has 5v crimp and requires the 5v on roof decking not slats....here's the picture; do you agree its 5v crimp?

brian

Originally Posted by brianmiller

I've always have seen metal roofs installed onto a roof decking system with an underlayment. Is it acceptable to install a metal roof onto 1x4 slats?

thanks,

brian

Originally Posted by brianmiller

the home's age is 1989....spacing is about 4 feet on center.

Regardless 1x4" decking slats aren't acceptable. 5/4 x 4" slats are acceptable decking still not if just 4' OC supported (24" OC), if hitting nail penetrations full 1" + nail penetration into 2"x + structure stock on panel sides. 2x4"s on flat 24" OC is what Scott's PDF said as a minimum even if overlay on existing decking and old roof covering or a raised roof (for coolness & less condensation). You'd still need 24" OC and 2" stock on flat for maximum stability but 5/4 is acceptable with low snow/rain loading on lower structures.