If you want to install steel over asphalt your best choice for installing metal roofing is to use a steel shingle system like the one shown instead of the more common and more expensive standing seam steel.
Installing metal roof panels over shingles.
Yes you can install a metal roof over shingles.
Installing the metal roofing over 1x4 s allows the ability to also install additional insulation under the metal roof.
This is what it looks like when you install a steel shingle roof system over an existing asphalt shingle roof.
The second way to install a metal roof over a shingle roof is with the use of purlins or battens.
In a standing seam roof long single panels run vertically all the way from the eave to the ridge.
Place a sheet from top to bottom on a section of the roof.
Building officials in some areas will only allow a re roof over one layer of shingles while officials in other places may allow you to place the roof over two layers of shingles.
Venting the eaves to vent the roof holes are cut in the old roof above the soffit which pulls air through the soffit vents underneath.
Use 1 4 inch metal wood screws to attach the metal sheets to the wood slat board base.
It provides a solid flat surface to attach the new metal roof to it creates an air gap between the back of the metal and the shingle roof which allows for airflow.
The purlins are screwed or nailed down to the roof deck depending on how the metal roofing manufacturer has testing for their roofing panels and then the metal is installed to the purlins.
Work up from the initial row starting at the lower corner in a diagonal pattern staggering the shingles to prevent gaps.
Most metal shingles will be attached to the roof using metal shingle.
Install metal roofing sheets.
Metal roofing sheets have to be installed one at a time.