It s good to know that you can only choose this option if your roof has not been overlaid previously.
Overlay shingles roof.
When you overlay a new roof you attach the new shingles or other roofing material to the existing roofing material.
An overlay roof occurs when keep your existing roof as is choosing instead to shingle on top of it.
This has advantages and disadvantages and each of those should be weighed carefully.
That said overlaying asphalt shingles with a metal roof could be an option provided there is no underlying damage.
What you need power nailer or roofing hatchet tape measure roofing shovel or flat pry bar hammer drill carpenter s square straight cut tin snips utility knife chalkline broom.
In general overlaying a new roof takes less time less labor and thus less money.