Hi
Must be stamped the rackings plans by an engineer before starting the construction?
regards
Yeah like others have pointed out it really depends on the AHJ.
For example, in Seattle they have an guiding document on when a building permit is required. If for example, the pv system is not 18" over the roof line, and does not exceed 5psf, then a building permit is not required, only an electrical permit. Of course there are a bunch of other qualifying criteria. But in some cases, you could have a hybrid ballasted system (with some attachments) to get down to less than 5 psf and comply with their rule to not have a building permit.
However, I would still want an engineer's stamp to provide some level of comfort so I can sleep on those windy nights, that it won't be blowing off the roof. So regardless of the permit, I would want it stamped. But my opinion might differ based on the racking system, ballasted, sure lets get it stamped; fixed attached, probably not, especially on a newer built home and doing staggared attachment layouts 2 and 4' on centers, what I would call a conservative standard approach to fixed attached.
On a separate note, depending on the racking you are using, the company may already have stamped letters from your state, or even calculations and guiding tables on overhangs, spacing, cantilever, etc, on how the racking system can be soundly integrated into a building when their guidelines are followed. Unirac, Ironridge, and Snapnrack are few off the top of my head that I know have these resources available on their website.
Still, in my own opinion, I will usually opt for the extra $800-$1000 to have the design stamped by an engineer, depending on what it is. It is cheap insurance to know you are doing the job right, at least, according to the structural engineer.