new shingle roof -- tear off or not?
#21
Overlay is entirely viable in your state, but it tends to shorten the lifespan of the roof. The extra weight isn't really an issue, but the ability to shed heat is. You end up cooking the shingles out of both sides. Can also cause the sheathing to delaminate if it is ply or OSB.

If you are going with comp 3-tab over more comp 3-tab, you might be looking at about 10-15 years out of the overlay before it should probably be replaced. Some parts of KY might let you go up to three layers, though I wouldn't recommend it. That's a lot of added material with very little holding power. You end up with a nail that doesn't have a lot of bite on the sheathing. The guys that do overlays correctly also know to dial the pressure back on their guns, otherwise it is very easy to deep-set a nail right through the overlay shingle.

It will most likely take the roofers less than an hour to strip it. They will probably just run a roof rake down the slope and into their dumpster or trailer if they can park it close to your eaves.

If anyone recommends staples on an overlay instead of nails, call them your choice of obscenities and slam the door on their face.
Math is tough. Let's go shopping!
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#22
I've done it both ways and will always do a full tear off. You can check the condition of the decking, replace tar paper with much better products, and the new shingles will last much longer!
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#23
I've also done both, and will never do it again with a complete tear off. The longer life is the chief reason.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#24
fredhargis said:


I've also done both, and will never do it again with a complete tear off. The longer life is the chief reason.




you mean without?

Reality is that which, when you stop believing in it, doesn't go away. - Philip K. Dick

Mark

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#25
reroofing my barn right now, and I'm doing a full tear off (all the way down to replacing the rafters)

After tearing off the shingles, its amazing how bad the plywood is in sections and I couldn't tell until the shingles were off....the shingles looked fine (for 30+ years old) but the plywood underneath in spots was all rotted to the point I'd go through it it I put my full weight on that spot. I doubt the nails were holding the shingles on in those spots.

Reality is that which, when you stop believing in it, doesn't go away. - Philip K. Dick

Mark

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#26
meackerman said:


[blockquote]fredhargis said:


I've also done both, and will never do it again with a complete tear off. The longer life is the chief reason.




you mean without?


[/blockquote]

Yep, fingers weren't doing what the brain told them..... I'd apologize but I'm old and make such mistakes on occasion.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#27
Check your local building code. Where I live only two layers are permitted.
No animals were injured or killed in the production of this post.
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#28
I hate to be gross---but to me, putting a new roof over the old is like putting on brand new clothes with dirty under ware!
Dave
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#29
tear it off. here code is only one layer. gives a better looking longer lasting roof if you tear the old one off first. run the roofers off if they want to use staples.
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#30
i personnaly didnt like going over existing shingles. if any are buckled/cupped that will show in new shingles.
if mold/moss on old shingles its not good to cover it up.
old roof may have only had felt paper on entire roof and i prefer at least one row of ice and water along edges and in valleys.
old shingles can hide damaged/rotted decking.
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