# Metal roofing question.



## idonutn0 (Nov 18, 2011)

I'm new to this community and have made a few posts on here. I havent started homesteading yet because Fannie Mae wont get off of her overinflated ----- and get the paperwork done so I can close on my new home! Sorry for that, but closings been extended three times now. :badmood:

Anyway, one of my first projects is to install a metal roof on top of the shingles that are currently on the house. My plan is to lay down a layer of tar paper on top of the existing shingles, and then put on some 1"X4"s down to attach the metal to. My question is this, do I put down the 1x4's only horizontally like in the top drawing below, or, do I set up a perimeter around the entire outside edge of the roof with the 1x4's and then run the horizontal boards inside that like in the very bottom drawing?

Doing it the first way leaves the ends exposed and a gap between the two roofs. Doing it the second way is the same, however, the ends are closed and it looks better in my opinion. 
Which way is the correct way of doing this?

Thanks for the help,


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## Elevenpoint (Nov 17, 2009)

Bottom....nice clean finished look.


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## am1too (Dec 30, 2009)

I would run the furring strips horizontal. You can run some vertical strips on the ends to make it look good and better tack the edges. Personally I would tear off the old roof shingles then you prolly won't even need the strips. Makes for a lighter roof for a better snow load, too. If you have a dirt drive take the nails out and put the shingles on the drive way.


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## jander3 (Feb 20, 2011)

Get pole barns screws that are long enough to reach the plywood under the shingles. Put the metal right on the old roof, don't bother with the strips.


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## Evons hubby (Oct 3, 2005)

jander3 said:


> Get pole barns screws that are long enough to reach the plywood under the shingles. Put the metal right on the old roof, don't bother with the strips.


Yeppers, this is the way I would do it. It relieves you of condensation and ventilation issues. The longer screws really arent that much more expensive. Your idea of the tar paper is good though... that will keep the gravel on the shingles from wearing through the metal roofing.


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## TnAndy (Sep 15, 2005)

The end strip running vertical won't be needed, and won't be seen if you use a rake trim piece ( which looks like a 90 degree corner ) that covers a couple inches on the metal, and laps down over the existing gable rake board......and you DO want to use that rake trim as it REALLY helps keep wind from lifting that edge on the metal down the road, in addition to making the whole thing look better.

The use of 1/4 strips or not will depend on what type of roof decking you have under the existing shingles....if it's simply 1/2" plywood or even worse, OSB, then I would definitely furring strip the roof....here's why......thin roof sheathing simply doesn't hold metal screws well.....you look at a roof with a thin sheathing in a couple years, and you'll see all kinds of screws backed out anywhere from a 1/4 to 3/4" where the roof metal expanded and lifted the screw out because ( I think ) the decking it was screwed into simply didn't have enough material to hold the screw.

SO, look at what type of decking you have, and unless it's solid 3/4" lumber ( old style ), I'd use a furring strip, and make sure you screw/nail the strip into the rafters.


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## idonutn0 (Nov 18, 2011)

Thanks for all of the answers.
The existing roof is tongue and groove and is exposed on the inside, so long screws will poke through. The wood is about 3/4 inch thick. With the strips down first, I can secure those with a 1.5 inch screw and then use a 2 inch barn screw to hold the metal without poking through the inside ceiling.
I was planning on using the barn screws with the rubber gasket to keep water from getting through screw holes. I also planned on the rake trim/flashing for the edges.
The reason for keeping the old shingles on the roof is because its an extra layer of insulation. I'm about an hour north of Houston, so snow weight isn't a consideration. (wish it was)


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## dirtman (Sep 15, 2011)

I am a builder in northern Michigan and have done alot of these metal roof overs. I'm not sure about texas but here we prefer no space under the metal as mold can build up. Metal directly on shingles will telegraph all the laps on the shingles. If I use furring strips I fill in between them with rigid insulation boards. Another option is to cover the roof with 5/16 OSB or better yet. strip the shingles. You can get one inch gasketed screws so you won't penetrate you finished ceiling.


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## Wylie Kyote (Dec 1, 2009)

idonutn0 said:


> Thanks for all of the answers.
> The existing roof is tongue and groove and is exposed on the inside, so long screws will poke through.
> The reason for keeping the old shingles on the roof is because its an extra layer of insulation. I'm about an hour north of Houston, so snow weight isn't a consideration. (wish it was)


From what you have said I would be using your #2 sketch with 2" to 3" gable flashing.

The other alternative is to locate the line of your rafters and use longer screws to secure the roof sheeting into the rafters. This would be far better if you live in an area with high winds.

Wylie


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## Seymour (Dec 15, 2011)

i would use the bottom picture but definetly use the 1x4's if not 2x4's! the more dry air space under your steel the better! if air flows under there then it will clear out excessive moisture and keep the steel from rotting. i also agree with the trim for the edges. i wouldn't worry about the tar paper it won't really do anything. never put steel roofing on without rubber washers on your screws, unless you want it to leak!


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## MO_cows (Aug 14, 2010)

The screws shouldn't poke thru your finished ceiling because the framing should be at least 3 1/2 inch dimension lumber (2 X 4). The ceiling material is attached to the underside of the rafters, the sheathing and roofing is attached to the top side. There should be 3 1/2 inches in between, hopefully full of insulation. So don't let that stop you from laying the steel right on the shingles. You don't have to worry about the shingles chafing the metal because once it is installed, it doesn't move. 

If your sheathing is good and solid, and if you mark where the rafters are and get screws down into them whereever possible, it is perfectly fine to lay the steel over the shingles. We did that on our garage at least 10 years ago, no problems yet. One old shed of ours, we put steel right over cedar shake shingles and it has held up for even longer than the garage.


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## travis91 (Jul 26, 2005)

here in south alabama we dont use 1x4 under the metal just put the metal right on the shingles. reason being is in the humid hot summers condensation builds under the tin if there is a 1x4 there, and it will build up on the 1x4 and rot it out and when they rot the roof will drop and allow a gap to form between the tin and the screw head


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