Any metal roofing experts?

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C

craigerlitz

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I have been told by several people not to use sheathing on my roof. They tell me to either use purlins over the trusses then a felt backed metal roof or purlins over the trusses with a foam board then a regular metal roof.

I planned on using plywood sheathing for 2 reasons. I'm not too fond of heights and it would provide a solid floor to walk on. The second reason was for dampening the sound when it rains.

Please tell me your thoughts on this. How would you do this?

Thanks,
Craig
 
We used plywood on my lakehouse,then had the local Amish install the metal roof.Worked great.........................................Jeff
 
The NY army Corps of Engineers has designed many military buildings with plywood sub decking and metal roofing on top of it without problem, however if you do this, you must use ceiling insulation somewhere under it all or you will get condensation on the underside of the plywood deck. This could cause it to rot.

Personally, I would design a commercial building with a metal roof to use a metal subdeck with rigid isocyanurate deck insulation over it. It is pretty common also to install the metal roofing panels directly on purlins, if the roofing is heavy enough gauge to carry to load of the workers installing it. This is normally the case as it must be able to carry a snow load. But again you must install insulation below it to not only keep in the heat and cooling, but to avoid underside condensation. It also cuts down rain noise pretty effectively.

The bottom line is normally cost of what you want to do.
 
New homes here often get metal roofs... Always have solid sheeting underneath. But I believe they use 3/4" plywood.
 
A metal roof, on a heated building, needs felt & osb under the metal. Don't be surprised if you see water running off of the felt.....if any heat gets thru the insulation it will cause condensation on the bottom side of the metal...
 
You didn't say what you are roofing. To me that would matter. Is it a heated home or garage, or an unheated shop building? What style of roof, and how much ventilation is already provided for?
Also, you mentioned that you don't like heights and wanted a solid deck to walk on. When I put a metal roof on my new shop/garage, it went directly on purlins. With a 10/12 pitch, it was like using a ladder - a lot easier and safer than if decking was there.
C
 
When we get around to finishing our house I am going to have the metal roof removed again....the felt torn up and replaced with the rubberized Ice Dam roofing membrane. Our building has a sealed, non vented style roof. Unless a spray foam insulation, high dollar in this area, is done it is going to be impossible to stop all the heat form escaping. In the heating months we have a bit of water traveling between the felt and the metal. Can't help but wonder how bad it will be if we get several feet of snow again. The Ice Dam membrane is a rubber underlayment. Have talked to my buddy that is going to re-roof the house for us and he told me that he went a full winter with just the Ice Dam membrane on his roof, no metal on top of it. He had zero problems with it. And he lives in the snow belt 25 miles north of us so....
 
what happens if you tin over existting shingles?
was thinking of strapping my roof with 1 by 3 and tinning it?
 
Wheels said:
what happens if you tin over existting shingles?
was thinking of strapping my roof with 1 by 3 and tinning it?
Click to expand...

Is it heated? If so and it is not insulated/insulated poorly you will have a crap load of condensation between the two roofs....
 
Wheels said:
what happens if you tin over existting shingles?
was thinking of strapping my roof with 1 by 3 and tinning it?
Click to expand...

they went over my old roof they will only do it if it has 1 layer
i am happy
 

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Wheels said:
what happens if you tin over existting shingles?
was thinking of strapping my roof with 1 by 3 and tinning it?
Click to expand...

Back when we had the tornadoes a while back I was listening to the scanner an there was a call that came in about a collapsed house out in the county. Emergency responders went to the scene to find a metal roof pretty much intact. It had been lifted off a house then landed in a field and it just had shingles that it had been attached to because the screws weren't long enough to reach any structure of the house.
 
Mine is metal roof on perlins and no sheeting. It was done 29 years ago. still no problem. You do need an airspace between the insulation and the metal. That is the purpose of a roof vent. I do not seem to get condensation only in the car port where there is no heat. Mine is well vented and I live on top of the mountain here in PA. Never a problem. By the way it is easier to stay on a roof with perlins than a sheeted roof. It like being on a ladder.
 
Oh and I am not an expert by any sort but I live in Amish country and I asked a lot of questions before I did it. And put the screws in the valley not the ridge.
 
clhyer said:
You didn't say what you are roofing. To me that would matter. Is it a heated home or garage, or an unheated shop building? What style of roof, and how much ventilation is already provided for?
Also, you mentioned that you don't like heights and wanted a solid deck to walk on. When I put a metal roof on my new shop/garage, it went directly on purlins. With a 10/12 pitch, it was like using a ladder - a lot easier and safer than if decking was there.
C
Click to expand...

This roof would be for a garage. It will have heat, but not for a year or two. The roof would be a gable roof with a 5/12 pitch. Ventilation hasn't been worked out yet. As for the heights, I am fine if on anything solid.

Thanks,
Craig
 
Oklacarcollecto said:
As Doug (inkjunkie) said felt is applied over the decking before the steel sheeting is the way it is done here.
Click to expand...

One type of metal roof I inquired about already has felt applied to it somehow. From what I've been told the plain metal roofing doesn't need the felt if used with the foam board.

Thanks,
Craig
 
Wheels said:
what happens if you tin over existting shingles?
was thinking of strapping my roof with 1 by 3 and tinning it?
Click to expand...

I read that the metal will expand and contract causing the granuals to abrade the underside of the metal.
Makes sense, by it probably will still outlast me. I did it on my barn roof becauseI didn't want the tear off.
 
My neighbor replaced his shingles with metal roofing. He had an unforeseen issue I will share... A good rain would run down with so much momentum that is cleared his existing rain gutters. As always, One thing leads to another.
 
Experts?? Around here?? You're kiddin right?? I'd be willin to bet we got an expert around here could tell you how to wipe your own *** better. We got more self proclaimed experts than any place I ever seen.
 
RustyRatRod said:
Experts?? Around here?? You're kiddin right?? I'd be willin to bet we got an expert around here could tell you how to wipe your own *** better. We got more self proclaimed experts than any place I ever seen.
Click to expand...

Rob, you're not still trying to do it sideways, are you? Lol

C'mon man, fact is, we DO have a lot of experts here on this site. And you're one of 'em. The great thing about it is the many opinions offered. Let the OP do his own research of course. But it is great to get the input from several others with similar experiences.
 
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