How to desk-check a rooftop candidate before the structural survey
A rooftop candidate lands in your queue with an address, a parcel number, and maybe a photo somebody grabbed off a real estate listing. Before you pay a structural engineer to climb up there and run numbers, you want to know if the building is even in the right height class for the search ring. That's the desk check, and doing it well is the difference between sending out three structural surveys and sending out one.
What the desk check actually needs to answer
RF wants a centerline height. Structural wants a roof to put a mount on. Before either of those conversations starts, you need a rough read on how tall the building is and how many floors it has. Storey count tells you fast whether this candidate clears the minimum elevation the search ring needs, or flags a four-storey walk-up that was never going to work and the broker just didn't mention it.
A rooftop candidate screening checklist usually starts here:
- Approximate building height and storey count
- Roof type (flat, pitched, mechanical penthouse, existing antenna farm)
- Parcel ownership and whether it matches the contact on file
- Zoning overlay or any obvious historic-district flag
- Distance from the search ring centroid
Get the first two wrong and the rest of the checklist doesn't matter. A surveyor who shows up to a building that's six storeys short of what the RF team needed has cost you a trip, a fee, and a week.
Where you can actually pre-qualify without a site visit
County assessor records give you a rough square footage and sometimes a stated number of floors, but they're often years out of date, especially for anything built or added to after the last reassessment. Permit history helps if the jurisdiction keeps a searchable database, but plenty of smaller municipalities don't, and pulling one parcel at a time by phone doesn't scale when you've got a dozen candidates to rank this week.
Street-level imagery tells you more than records do, if you can see the building clearly. Shadow length in overhead imagery is the classic workaround when you can't get a street view angle, and it's been used informally for decades. The problem is it's slow to do by hand across a candidate list, and it falls apart on buildings that are shadowed by something taller next door.
This is the gap Storey Estimation is built for: a per-building height and estimated storey count pulled from very high resolution imagery, refreshed annually, so you're not reverse-engineering shadows on a case-by-case basis or trusting a tax record from three renovations ago. You drop in the candidate list and get back a height value you can rank against the search ring requirement before anyone picks up a phone.
Where the desk check runs out of road
A desk check tells you whether a candidate is in the right height class. It doesn't tell you the roof deck condition, whether the parapet can take a penetration, or what the load path looks like from roof to foundation. That's structural engineering, and no amount of imagery review replaces a licensed engineer signing off on a mount design.
What the desk check does is sort your candidate list so the engineer's time goes to buildings that already clear the basic height test. If you're running five candidates per search ring, a height pre-qualification step that kills two or three of them before the survey stage is a real reduction in what you spend on site visits that end in "this one doesn't work."
Pull a per-building height read before you commit survey budget and the structural survey becomes a confirmation step, not a discovery step.
If three candidates on your list need a height check this week, that's exactly what Storey Estimation was built to answer.