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Metal Roofing INSTALLATION question

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Metal Roofing INSTALLATION question

Old 09-25-2020, 12:46 PM
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3 things that are super important!!!!!!

1: take off the 3 tab junk down to the plywood (replace any bad sheets)

2: Put down 55 to 60 mil peel & stick down over the entire roof even over any hip and valleys.

3: if you are using screws through the roof onto the plywood ONLY use ZAC SCREWS!!!! Do not let them talk you out of it, ZAC only!
Old 09-25-2020, 12:59 PM
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If it was mine I would have the roofer remove the shingles and install a new underlayment (felt or synthetic) over the existing decking. At that point you can decide if you want the 1x4 nailers (what does the manufactures installation instructions say?). I would think that a metal roof installed over the shingles would cause moisture to be trapped.
Old 09-25-2020, 01:11 PM
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Originally Posted by buzzellc View Post
If it was mine I would have the roofer remove the shingles and install a new underlayment (felt or synthetic) over the existing decking. At that point you can decide if you want the 1x4 nailers (what does the manufactures installation instructions say?). I would think that a metal roof installed over the shingles would cause moisture to be trapped.
Good points. The roofer said that the nailers leave an air space that can cause wind to get under the roofing and lift it, whereas screwing directly to the roof's surface eliminates that. Moister is a question, but where would moisture come from?
Old 09-25-2020, 01:17 PM
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Moisture will be coming from inside the house and possibly condensation from the different temperatures and humidity (above and below) the metal roof. The underlayment (felt or synthetic) is somewhat breathable to allow the trapped moisture to escape
Old 09-25-2020, 02:11 PM
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It can be done, just don't be surprised if it doesn't last. The roofer I use only does standing seam because he says the screw down metal doesn't last any longer than shingles. The metal its self may, but the rubber washers on the screws don't.

Also there were houses here in florence where the metal came off. There just isn't much for screws to bite in the sheathing. Especially if it's old and dry. I'd recommend 2x nailers. 1x tend to split if you don't pre-drill. But on a house you won't know that until the roof pulls up or screws leak.
Old 09-25-2020, 02:19 PM
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Disaster waiting to happen.

That metal gets hot - like really hot and will degrade, rather quickly, any asphalt product underneath. Will contract and expand.

Should be a tear off, Hi-temp wintergard and then new metal.
Old 09-25-2020, 02:30 PM
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Originally Posted by onokai View Post
The boards seve several purposes. !st strength. They are screwd to the Rafters not the weak roof shingles. Second they provide air space so when roof sweats it drys underneath -metal can sweat.3rd tney provide a sound barrier for rain and other noise.
SDure you for go this and save as in any construction you can save by not doing it right.The best way is strip the old roof put down a sound insulation barrier and use the 1x4 and do it right. But since its an apartment building for rental money we know it will not get done right.
This is what my roofer did 15 years ago at our lake home. No problems and still looks good.
Do it right, do it once.
War Eagle!
Old 09-25-2020, 03:33 PM
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Originally Posted by Shore Native View Post
Disaster waiting to happen.

That metal gets hot - like really hot and will degrade, rather quickly, any asphalt product underneath. Will contract and expand.

Should be a tear off, Hi-temp wintergard and then new metal.
What's your $$ estimate of doing it your way and doing it the OP way for a 3,000SF roof?
Old 09-25-2020, 03:40 PM
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1) ALL metal roofs fasten to the sheeting

2) Go by the roofing/reroofing code. The secret is adequate slip sheet between the metal and the shingles

3) You may need longer screws
Old 09-25-2020, 05:05 PM
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I have a number of homes and apartments to re-roof all at once, so cost is definitely a factor in the decision. I also don't expect to own them for another 10 years, so longevity isn't a factor. If I pay for the premium product, then rents will have to go up in order to pay for the cost, and I'm not inclined to do the caviar menu when i know that tenants would rather have a dry roof without having to pay for a long-term dry roof. Hope that makes sense to some of you.
Old 09-25-2020, 05:25 PM
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Originally Posted by bamaboy473 View Post
modest apartment buildings that need shingles. A roofer said that metal is almost the same price as 3-tabs, so I'm leaning that way. .

If you go asphalt shingles i wouldn't do 3 tab They don't even meet code here, but the price difference between that and Architectural is minimal
Old 09-25-2020, 08:41 PM
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A lot of opinions here with too many variables, metal over, tear off, furring strips, no strips!
My roof didn't leak, insurance companies go nuts over age of a roof.
I had them put down synthetic felt to add another layer of waterproofing and to protect the underside of the metal.
They also installed ridge vents which will add to the life of the metal.
Mine is permitted and inspected, if it is good enough for the county it is good enough for me!
The State of Florida has really upped the codes since hurricane Andrew in the low 90's.
Old 09-26-2020, 05:16 AM
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Code = the bare minimum.
Old 09-26-2020, 05:42 AM
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You should always have a gap between the metal and the roof surface to allow it to breathe a bit and keep moisture down.
Metal roofs are very forgiving to mild variances.
Old 09-26-2020, 06:14 AM
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Originally Posted by bakerjw View Post
You should always have a gap between the metal and the roof surface to allow it to breathe a bit and keep moisture down.
Metal roofs are very forgiving to mild variances.
Not necessarily. I've NEVER seen it done, but Florida code requirements may be differemt. It's all about preventing the roof from blowing off.
Old 09-26-2020, 06:59 AM
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Old 09-26-2020, 07:10 AM
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Do what pierdude said above! Do it right once!
Old 09-26-2020, 07:42 AM
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Your location gets it's fair share of tropical storms, hurricanes and daily afternoon t-storms in the summer that will test any roof you install.

Not sure going "cheap" on a roof is the smart way to go.
Old 09-26-2020, 07:57 AM
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Not sure about your area but I would guess $1.00/sq/ft. for the tear off. Also agree that 1x4 or 2x4 strips are way better. I bet the roof sheathing is 3/8" plywood, most apartments were.
Old 09-26-2020, 08:09 AM
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Most Florida roofs/reroofs are designed to withstand 150mph or more. Only roof which really holds is metal.

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