The quality and type of underlayments used on the project in the long term will affect the overall performance of the roof.
Leaving shingles under metal roof.
Metal roof flashing will still be needed around chimneys skylights and where roofs hit a wall sidewall endwall.
It doesn t matter if the air space is a half inch or six inches because the condensation factor will remain the same.
Overgrown trees debris and even snow can scuff up the surface.
The roofing is manufactured in panels that.
I would argue that putting sheet metal roofing over existing shingles if going to always look just at leat a little bit junky because the surface they are starting with is uneven and somewhat compressible.
Every situation will be different but generally speaking installing one of the more heavily textured metal roofs such as a corrugated vertical seam or or a horizontal metal shingle over your existing shingles should not be a problem.
Even if you leave your shingles you will need to remove ridge venting material and caps.
Well that s why the metal roof is such like an eco friendly product because you don t have to get rid of all of that stuff to the landfills.
Installing wood stripping under a tin roof.
At some point during its lifecycle you can expect the metal panels to get scuffed or scratched.
But now that i said that i would tell you that if it was my house i probably would and the reason is i don t want to have all those old shingles under the roof.
Tin roofing also known as metal roofing is considered more durable than composition or wood shingles.
However before you decide on reroofing with a metal roof you have to keep in mind that there are specific conditions that make reroofing with a metal roof safe.
In addition metal roof pipe flashing will be needed for round pipes and penetrations.
However scratches down to the metal can be problematic.
In some instances this can lead to punctures and tears that result in leaks.
You will want to install layer of underlayment between the old and new roofs.
1 remove the shingles before installing the metal roof the first way to install a metal roof over shingles is by completely removing the old shingles before installing the new metal roof.
Some roofing contractors recommend reroofing with standing seam metal because the total roof weight is but a fraction of a standard asphalt shingle roof which helps preserve the roofing integrity.
A benefit to doing it this way is that you can see if there is any rotten plywood that needs to be replaced before installing the new roof.
Several of the contractor responses say why not leave perfectly good shingles under the metal roofing rather than remove them.