There are two questions that must be asked when adding anything to a roof.
- Can the roof/ building/foundation handle the additional load?
- What keeps the new load from blowing away?
It is assumed that a licensed solar installer can answer these questions. If he/ she can’t, he/she will need to find somebody who can. A licensed engineer is the easiest solution. Some of the racking manufacturers have guides to calculating a code-compliant install as well. Many variables must be considered and determined to complete the calculation. The spacing between mounts has the variables of: strength of rail, distance between parallel rails, cantilever of modules over rails, pull-out strength of mount, shear strength of mount, slope of roof, height of roof, wind zone, roof type, structural integrity of roof framing, etc. The only values in the variables above that we can provide are pull-out strength and shear strength of mount. We provide structural test reports on all of our mounts, available on our website. You will need to gather the rest of the applicable information and do the calculations for your specific project.
Source: Quick Mount PV