Stone coated metal roofing uses an acrylic bonder to secure "stones" to the panels. They are then coated with a clear acrylic top coat. Do you really want to trust an acrylic paint to protect your home? As far as we know, there has never been an acrylic that will hold up to the constant punishment by the Sun and it's UV rays. When the clear coat and bonder begin to break down, the "stones" will come loose and end up in your gutters, leaving unattractive discolored and unprotected spots.
Since the "stones" that are used are a natural resource, and not synthetic, often times you will have a hard time keeping the color consistent from batch to batch. You can end up with a roof that has some off colored areas. The picture below is and example, and the manufacturer considers this acceptable.
Once that acrylic breaks down, the "stones" are then unprotected from the elements, and below are a few examples of Burnout and Granule Loss.
The biggest problem with stone coated metal roofing is the fact that the panels are non interlocking(panels overlap) and are through fastened(nailed from the outside) instead of having panels that interlock and have concealed fasteners like ours do. The problem with a non-interlocking design is that there is an open path for wind, rain, and snow to get through to the decking. The problem with exposed fasteners is that they are EXPOSED to the weather! Through-Fastened roofing opens a direct path through the roof that water can follow.
Once those galvanized steel fasteners start to rust, they will lose their strength, and then that panel will be free to move around, and eventually will fail. We use stainless steel nails that are covered by the panel above it, leaving no exposed fasteners.
Another problem with these roofs is that they are often batten mounted systems, which involves strips of un-treated wood that are nailed across the roof, and the panels are nailed to them. These strips are prone to rot from trapped moisture. Battens also provide a collecting point for condensation and water that comes in at the fastener points and through overlaps between panels.
A problem that a lot of people have with a batten system is that bats like to take up residence in the void between the panels and the decking. More than likely, this is a problem that you would not want to have!!
The photo below shows where snow has blown behind the shingles and rested between the battens.
The last problem with Stone coated roofing, is that even though the contractor will tell you that these roofs are walkable, they are NOT! Without a lot of experience, you will dent the roof badly, as seen below.