Unsure about this roof


It’s a old farm house, parts of the house was build in 1900. The asphalt shingle roof appears to be in good shape. (6-10 years old)

When you look at the roof from the attic. There is an old metal roof and boards, No sheathing? My question is to install shingles over a metal roof wouldn’t you put sheathing on the metal roof then the shingles? Is it better to completely remove the metal roof or is it better to keep it as support???
One of the photos show a hole in the metal roof and it looks like sheathing?

Please see Photos

Thanks for your Help








Looks like a handyman special to me… If it is 6-10 years old, and isnt leaking, I would file this one under “irregular instalation” and inform the client that the life expectancy of the roof has been shortened by the lack of willingness to pay a contractor, and advise him not to make the same mistake when he re-shingles it. The rusting nails are not good, and always remove metal before re-sheeting:)

Thank You Michael for your response. I have to tell you I have never seen this. One question is snow load? Is this installation strong enough?


I’m surprised to see that the shingle field is not wavy from that installation. I’d simply report that the shingles we installed over metal roofing which is improper.

Proper installation would consist of simply removing the metal material, filling all the holes for the roof backing and then installing the shingles (with proper ventilation).

Where’s the venting?

We can not determine the adequacy of snow loads on a roof. I simply look for signs of settling throughout the roof field and the underside rafters.

Thank You David: I agree it’s time for a licensed, certified, insured, roofer

You won’t find a licensed roofer in my area. They are licensed construction contractors who have no absolutely no clue how to install an ideal roofing system. Most roofers here in Massachusetts are hacks.


Are you sure they didn’t overlay metal with thin ply/OSB for nailing surface?

Was drip edge flashing present?

Did you look at eave/rake???


Now that (IMO) would have been one idiotic move if they did. Trying to secure nailing to a plywood sheet with metal roofing on the underside is definitely a brainless move.

Barry…I’m not stating that this can’t be done as I’ve seen many brainless acts in my life.

Hi Barry:
One of the photos has a hole in the metal roof and thru that hole is plywood. I beleive your correct that they installed sheathing ove the metal roof as a nailing surface. The shingles look even and have lasted years. Some nail are loose and some have rust on the inside of the attic. I followed David’s and Michael’s advise, and reported it as improper installation.

Thank You Guys it is really good to know you are there to help. I know this might seem simple to some of you but to me it was important that I got it right.


This is very common in my area (maui) with the older homes. Unitl recently reroofing required no permits. The biggest concern we have here is the framing for a metal roof of this age, 40-50 years, is much lighter than the current standards for an ashalt shingle roof. Engineering is never performed on the roof sturcture before the new roof is installed and then throw in some termites and the hole roof structure needs to be rebuilt.


To keep the “flat look” on the exterior over the metal roof they would of had to install spacer boards inbetween the hat ribs of the metal roof. This is done on commercial jobs of steel over steel. I would not recommend, or do, this style of installation without an engineers evaluation of the snow load. As far as the shingle manufacturer, if it was redecked, the installation would be correct. If there is proper ventilation, which should be installed with any roof, I can not tell from your pictures.
Proper installtion should be checked on the exterior. Over weighting of the roof should be determined by a licensed engineer.


Just in case you did I wasn’t approving the method just asking because I’ve seen what Pat, Mark and Scott have verified.

Drip edge is the first place I look to verify substrate if not visible from the eave or rake edge depending on roof style.

Thank You Scott. I have learned alot from this thread.

Thank You Scott. My initial concern was snow load. My report advised the client to have a engineer evaluate the roof. The client rescinded his offer.

I am Now an official Deal Killer and proud of it :cool: :cool: :cool:
Thanks for everyones help