MF283
Platinum Member
It will allow more air through the ribs being it's not directly on the sheeting. 2X6 ON BARNS AROUND HERE & 1X4 on OSB as other's have stated.
Ronnie
Another Metal Roofing Question
- Thread starter Beltzington
- Start date
It will allow more air through the ribs being it's not directly on the sheeting. 2X6 ON BARNS AROUND HERE & 1X4 on OSB as other's have stated.
Ronnie
LD1
Epic Contributor
Dont worry about the metal spanning between the 1x4 strips. The ribs add strength and keep the metal flat. The metal spans 24" no problems and will support someone walking on it and remain flat. Thats how its done when attaching to purlins and and no OSB.
PILOON
Super Star Member
I did a demolition of a tin roof* that had been laid directly on plywood.
Roof was about 8 years old.
That roofing was so rusted from condensation that it had started to develop pin holes in some areas and the plywood underlay was useless as well being advanced rotting.
*This was a galvanized metal.
My wood storage shed is galvanized as well and in the spring you need to wear a raincoat as the condensation simply drips off like a rain storm. That is due to cold snow on the roof and warm humid spring air. However since the shed roof is open air it drys and not rust.
Metal in direct contact with wood simply sits in damp wet evvironment and rusts away.
Roof was about 8 years old.
That roofing was so rusted from condensation that it had started to develop pin holes in some areas and the plywood underlay was useless as well being advanced rotting.
*This was a galvanized metal.
My wood storage shed is galvanized as well and in the spring you need to wear a raincoat as the condensation simply drips off like a rain storm. That is due to cold snow on the roof and warm humid spring air. However since the shed roof is open air it drys and not rust.
Metal in direct contact with wood simply sits in damp wet evvironment and rusts away.
gsganzer
Elite Member
- Joined
- Jun 11, 2003
- Messages
- 3,035
- Location
- Denton, TX
- Tractor
- L3800 w/FEL and BH77, BX 2200 w/FEL and MMM
Go to Mueller's website and download one of their manuals. They show installation details.
Mueller Installation Manuals
Mueller Installation Manuals
gsganzer
Elite Member
- Joined
- Jun 11, 2003
- Messages
- 3,035
- Location
- Denton, TX
- Tractor
- L3800 w/FEL and BH77, BX 2200 w/FEL and MMM
Go to Mueller's website and download one of their manuals. They show installation details.
Mueller Installation Manuals
Mueller Installation Manuals
Deere Dude
Elite Member
- Joined
- Feb 10, 2011
- Messages
- 3,986
- Tractor
- John Deere 3720
Their preferred solution is to screw 1x4" strips to the sheathing to keep the metal off the roof which they believe will prevent moisture damage from condensation. Thinking this through, a problem of mine, any condensation will still end up on the sheathing so I do not see how this is a solution any better or worse than screwing it directly to the sheathing. Actual experience greatly appreciated, opinions will be tolerated.
I would think that moisture buildup would contact and corraled by the 1x4s and they would rot. I also would want this bubble wrap under the tin no matter how it was installed.
tallyho8
Elite Member
- Joined
- Aug 1, 2004
- Messages
- 4,998
- Tractor
- Kubota L4400, Kubota ZD326
I have an unconventional way of installing a metal roof that many may not agree with, but it works for me and it works well.
My shingle roof was damaged during hurricane Katrina so I installed a metal roof over it. As 1X4s aren't strong enough to hold the metal down during severe windstorms, I used treated 2X4s purlins at 24" spacing screwed down with screws rated for treated wood and made sure the screws went into the rafters. I nailed 3/4" foam insulation sheets to the roof between the purlins and this left a 3/4" air space. I cut strips of felt paper which I stapled to the 2X4s so the metal would not touch the treated wood.
I screwed the panels down on the flats and I did not use the foam filler strips that they use on low pitch roofs so that I would have good air flow under the metal. An advantage to this method is that my attic is now at least 10 degrees cooler in the summer and the roof is so well insulated that you can not hear rain falling on the metal roof.
My neighbor had a contractor install his metal roof using 1X4s and the next hurricane 2 years later blew the metal off one side of his roof breaking all the 1X4s that were holding it down or pulling out the short screws that went through the 1X4s. My roof was not damaged at all as the 2X4s were strong enough to not break and the longer screws did not pull out. Attached is a photo of his home after the hurricane.
My shingle roof was damaged during hurricane Katrina so I installed a metal roof over it. As 1X4s aren't strong enough to hold the metal down during severe windstorms, I used treated 2X4s purlins at 24" spacing screwed down with screws rated for treated wood and made sure the screws went into the rafters. I nailed 3/4" foam insulation sheets to the roof between the purlins and this left a 3/4" air space. I cut strips of felt paper which I stapled to the 2X4s so the metal would not touch the treated wood.
I screwed the panels down on the flats and I did not use the foam filler strips that they use on low pitch roofs so that I would have good air flow under the metal. An advantage to this method is that my attic is now at least 10 degrees cooler in the summer and the roof is so well insulated that you can not hear rain falling on the metal roof.
My neighbor had a contractor install his metal roof using 1X4s and the next hurricane 2 years later blew the metal off one side of his roof breaking all the 1X4s that were holding it down or pulling out the short screws that went through the 1X4s. My roof was not damaged at all as the 2X4s were strong enough to not break and the longer screws did not pull out. Attached is a photo of his home after the hurricane.
deezler
Elite Member
- Joined
- Jan 30, 2012
- Messages
- 3,470
- Location
- Southeast MI
- Tractor
- Cub Cadet 7305, Kioti CK3510seh TLB
Dang, I'm not real thrilled to jump in here and see such disagreement. I am preparing to build my pole barn this year (hopefully) and wanted to put metal over sheathing to A) strengthen the roof assembly, B) insulate a bit for noise and temperature, C) prevent condensation dripping inside the barn, and D) make insulating the barn roof interior a bit more straightforward.
However now I don't know how to do it. drat! haha.
Question: Why is there moisture under the metal in the first place? Condensation? screw holes in the metal panels? other leaks?
However now I don't know how to do it. drat! haha.
Question: Why is there moisture under the metal in the first place? Condensation? screw holes in the metal panels? other leaks?
KennyG
Elite Member
deezler, my opinion (which is worth the pixels invested here) is to forget the sheathing on a pole barn. If you think you need more strength, use 4 foot spacing on the trusses and cross brace them heavily under the top members. Install a ceiling under the trusses and you will have real insulation capability. Put on 26 ga. quality roofing per the manufacturers instructions and forget about it for the next 50 years.
LD1
Epic Contributor
Agree. Forget the sheething under the metal.
Its condensation that is what causes the issues. Look at ANYTHING metal outside. Look at your car and car windows on certain mornings. thats what the underside of the metal does.
Using osb to stop it from dripping on you....the moisture is still going to be there, only instead of dripping on you, it is saturating the OSB and it will fail sooner rather than later.
Leave the underside open with adequate ventilation, or use a vapor barrier.
As far as insulating, its best to insulate along the bottom chord of the truss as opposed to along the roof line. Which also keeps a smaller space to heat/cool as you arent climate controlling the "attic"
Its condensation that is what causes the issues. Look at ANYTHING metal outside. Look at your car and car windows on certain mornings. thats what the underside of the metal does.
Using osb to stop it from dripping on you....the moisture is still going to be there, only instead of dripping on you, it is saturating the OSB and it will fail sooner rather than later.
Leave the underside open with adequate ventilation, or use a vapor barrier.
As far as insulating, its best to insulate along the bottom chord of the truss as opposed to along the roof line. Which also keeps a smaller space to heat/cool as you arent climate controlling the "attic"