Check with the local building code department to find out what the rules are for installing metal roofing products. Make sure that you follow the codes regarding the installation of metal roofing over an existing roof.
If you decide to hire a contractor, ask family or friends who have had metal roofing installed for recommendations. You can also identify metal roofing products that appeal to you and ask the vendor to refer experience installers to you.
Read the product’s warranty. Some metal roofs products must be installed by certified contractors. A do-it-yourself (DIY) job may void the product’s warranty, so make sure you choose a product that permits DIY installations. Find out in advance what is required to install the product so that you can determine if it is within your capability to install.
DIY Installation Guidelines
When installing metal roofing over an asphalt roof, prepare the surface of the existing roof by removing the old shingles.Cut the material flush with eaves and roof overhangs. Remove the old flashing and to install new edge flashing. If any of the sheathing is damaged or structurally unstable, it must be repaired.
Sketch a layout out of the roof surface. Make note of how the layout of the panels will work around edges and along the ridge or peak of the roof. This way, you can make adjustments on paper and minimize any waste and avoid unnecessary cutting and bending metal as you move on up the roof.
Check out the underlayment requirement for the product that is being installed. Generally, a single layer of 30-pound felt paper can be secured to the deck. Usually, specific instructions are given on how to apply underlayment in the valleys, hips and ridge sections of the roof.
Generally, the installation starts at then eaves. Mark a straight line for the upper edge of the anchor strips. This will help align the first panels and ensure a straight and true metal roof installation. Secure the metal panels according to the guidelines, including the spacing and the number and type of fasteners
Do not use a pencil to mark on panels because it could lead to corrosion. Make your marks with masking tape, which is easy to see and remove.
After the panels are in place, follow the guidelines for installing the metal roofing trim. Typically, trim must be installed on the edges and along the peak of the roof.