I would say that in most cases less weight is being added to the home by the new metal roof than what the current shingles have lost due to granule wear and oil evaporation.
Installing metal roofing on top of shingles.
3 install 1x4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1x4 purlins over the shingle 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.
Install your metal edging around the perimeter of your roof.
Use 1 1 4 inch.
Most metal shingles will be attached to the roof using metal shingle.
This method has its benefits as well.
You will need to lay some 1 by 4 inch pine boards lengthwise every two feet on your roof.
Install the metal edging.
Make a slat board base on top of the shingles.
Lay the starter row of metal shingles at the drip edge and affix to the roof with metal roofing nails.
The purlins are screwed or nailed down to the roof deck depending on how the metal roofing manufacture has testing for their roofing panels and then the metal is installed to the purlins.
Yes you can install a metal roof over shingles.
As long as the plywood under the shingle roof is in good condition this way can provide many benefits.
The second way to install a metal roof over a shingle roof is with the use of purlins or battens.
Steel shingles weigh about 1 4 what asphalt shingles weigh and aluminum shingles weigh about 1 8 what standard shingles weigh.
In terms of performance many homeowners choose a steel roof making it the most popular option when it comes to creating a metal roof over existing shingles.
Installing metal roofing over shingles is the best solution.
However you ll want to check with your local building department before you make any decisions.
This is by far the most common way to install a metal roof.