One room is a scan. A house is a set of scans that have to agree about where they are relative to each other. On a single floor that is straightforward. The moment there are stairs, it gets worth explaining.
Scan the stairs, do not skip them
The staircase is the hinge between floors. Walking it as part of the capture — slowly, phone forward, turning at the landing — is what gives the two floors a shared reference. Skip the stairs and you have two correct floor plans with no agreement about how they stack.
What the stairs themselves give you
Honest expectation setting: a staircase comes back as a single volume, not as a tread-by-tread model. You get its footprint and the rise between floors, which is what a floor plan and a square-footage number need. What you do not get is a riser count or individual tread dimensions. If you are bidding stair work specifically, measure the treads.
Split levels and half flights
Split entries, bonus rooms over garages, and sunken living rooms are the cases where people expect trouble. The rule is the same: capture the transition, not just the two spaces. Walk the four steps down into the family room as part of the same pass, and the elevation change is measured rather than assumed.
Checking it before you leave
Spin the whole-house model once in the app while you are still on site. The stack is either obviously right or obviously wrong — a floor sitting at the wrong height is not subtle. Rescanning a staircase takes two minutes on site and an hour if you discover it from the office.
Practical order of operations
Ground floor, then up the stairs in the same capture, then the upper floor, then back down to anything you missed. One continuous walk, the way you would show a house to a buyer.
Houses are vertical. The measuring tool has to be too.