Structural
When do you actually need a structural stamp?
Short answer
Most jurisdictions ask for sealed structural calculations when something about the roof is uncertain rather than when solar is involved: a re-roof, tile or heavy coverings, undersized or unusually spaced rafters, a roof that already carries added load, high wind or snow exposure, or any ground mount. A straightforward array on a modern composition-shingle roof with conventional framing often does not need one.
What a structural stamp is
A set of calculations, sealed by a licensed engineer, showing that the existing roof framing can carry the added dead load of the array and the wind and snow loads at that specific site. It is not a sheet of boilerplate. It is site-specific arithmetic against the governing load criteria, which is why it is priced separately from the drawings.
When it is normally required
- Re-roofs. New covering plus array on framing whose history is unclear.
- Tile, slate and other heavy coverings. The existing dead load is already high.
- Marginal framing. 2×4 rafters, long spans, wide spacing, or anything cut rather than engineered truss.
- High wind or snow. Coastal exposure, or ground-snow loads that drive the governing case.
- Ground mounts. Essentially always, because there is a foundation.
- Jurisdictions that ask every time. Some simply do, regardless of the roof.
When it usually is not
A conventional composition-shingle roof, engineered trusses at standard spacing, a flush-mounted array within normal attachment spacing, moderate wind and snow, and a jurisdiction that does not require one by policy. On those jobs the attachment details and the load summary on the plan set are typically enough.
How to tell before you quote
Three questions, answered before the price goes to the homeowner:
- What is the roof covering, and is it being replaced as part of this job?
- What is the rafter size and spacing, and is it truss or stick framing?
- Does this jurisdiction require sealed calculations as a matter of policy?
The first two come from a photograph of the attic and a tape measure. The third comes from the jurisdiction's own submittal checklist. Getting all three before quoting is the difference between a $200 line item you planned for and a change order you have to explain.
What it costs here
A structural stamp is a $200 add-on to the standard plan set. The $250 base covers permit-ready plans for systems under 20 kW; the stamp is separate because the calculation work is separate. Tick it on the order form and the sealed framing plan and calculation package ship inside the same PDF.
If you are unsure whether a job needs one, send the roof photographs with the order and ask. It is a faster conversation before the set is drawn than after the correction notice.