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Tdoggy187 02-21-2008 10:15 AM

Metal roof???
I got a shingled roof. Looks like 4 layers. They are old and worn. I got someone who says we can put a metal roof right over them. Is this a good idea? Or should we have to do a complete tear of, put down some plywood, and then the metal roof? I'm not sure how metal roofs work exactly? Any help would be great. Thanks...:thumbup:

perpetual98 02-21-2008 10:31 AM

I'm curious about metal roofs too. I can't imagine anyone would tell you that it's OK to put a metal roof over 4 layers of shingles though. Maybe someone will chime in with some good links for metal roofs. :)

ajh359 02-21-2008 10:48 AM

I put a new metal roof on over the shingles, and put foam insulation on too. I see a big difference in the summer with AC not coming as much. The retailer I got it from leave the shingles on. He also said the lighter the color the more heat reflection you will get.

Ed the Roofer 02-21-2008 11:01 AM

That just seems insane to me, and probably against the code too.

The integrity of a metal roofing system depends on the flashing details and the fastening of the system. Going through that many layers of old, brittle and decrepit aged roofing shingles would seem that the fasteners would be too prone to back out due to expansion and contraction and also by the toggling effect.

That would not be adviseable and would probably cost you much more money to fix correctly in the long, or even short run.


ajh359 02-21-2008 11:43 AM

I only had one layer of shingles.

Ed the Roofer 02-21-2008 12:35 PM

I was referring to the poster who already has 4 layers on now, which already is in violation of any codes I know of.


Tdoggy187 02-21-2008 05:37 PM

Its a house...
Its a house in upstate NY in a small little town. I don't think its breaking any codes. I'm not positive though. We bought the house and it was like this. This roof must be at least 40 years old...

Guess I shouldn't put Metal up over 4 layers of shingles???:eek:

Ed the Roofer 02-21-2008 07:22 PM

It most definitely is against the national codes, which all towns reference, even if they do not enforce them.

You may be mistaken if you counted the layers yourself, because each layer of shingles look like 2 layers to the untrained eye.


Tdoggy187 02-21-2008 07:32 PM

ok so if it has 2...
Yeah i could be wrong. Maybe it only has 2 layers of shingles. Then can I just put a metal roof over it? Does this make a difference? Again it is a very old roof. And their have been leaks and water damage to ceilings inside...:eek:

wire_twister 02-21-2008 08:50 PM

Around here people will strip the roof with 1x4 lumber then install the metal on that, seems to work, but I wouldent care for the extra weight. I put a metal roof on my house when I built it, no plywood decking just 2x6 strips across the trusses and metal screwed down to the strips kinda like a barn roof. Oh, lest I forget to mention if you use this method count on r-40 attic insulation to hold out the cold.

Tdoggy187 02-21-2008 09:15 PM

here are some pictures please help guys
6 Attachment(s)
Pictures of the inside roof structure. Any advice would be welcome! Thank You all :thumbsup:

Tdoggy187 02-21-2008 09:22 PM

a few shots of the outside of the roof
6 Attachment(s)
The outside. :thumbsup:

And some of the damage it has done inside :eek:

roofboy 02-21-2008 09:29 PM


With the snow load that you may get each year I would advise you to tear it all off and start fresh. I install a lot of metal and the added weight of that plus the snow, plus the old roofing would be too much weight(IMO). Ed makes some very good points about the codes and such also.


the roofing god 02-21-2008 11:46 PM

new york should only allow 2 layers,and if it`s upstate we`re talking mega snow,basically you`re better to remove an old roof with moisture problems than to cover it and allow it to get worse underneath,possibly even grow mold,rip it fix damage,then do the metal-the guys are right,especially the guy who mentioned r-40 insulation,and the weight of the snow load as Keith mentioned

Ed the Roofer 02-22-2008 06:47 AM

With the amount of moisture that has already affected the rafters and decking, not to even mention the soaking of the insulation, this should be a "No-Brainer" to decide on removing the existing roof layers, whether 2 layers or 4 layers, just for the fact of repairing the wet and rotted wood and to have access to the attic to efficiently replace the wet insulation.

From your interior attic photos, I would guess that this home once had a cedar shingle roof on it, which lasted at least 50 years on top of skip shething, space board decking. Then, either after an additional layer of composition shingles were added, which would have lasted 20-30 years, the previous owner had the roofs removed down to the skip sheathing. The decking is now solid sheating, with either the gaps being filled in, or the new sheathing being applied over the spaced decking.

I doubt, from your photos, that you have 4 layers on there currently, but you still need to remove the old roofs to do the repair properly and replace the rotted sections. There also may be more evidence of mold growth gowing on, as the section of rafters in one photo clearly showed significant growth already.

When the roof is being done, ensure that you have a properly balanced system of fresh air intake ventilation and roof top, ridge exhaust ventilation.


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