How to tell shell completion from vertical construction in satellite imagery
If you're reading a comp set from a desk instead of a windshield survey, the hardest call isn't spotting a crane. It's knowing whether the building under that crane is still going up or already closed in. Those two states get lumped together as "under construction" in a lot of pipeline trackers, and that's exactly the problem. A site that topped out six weeks ago and one that's still pouring the fourth floor slab look similar at a glance from 400 miles up. They are not the same leasing risk.
What vertical construction looks like from overhead
During vertical construction, the floor plate is open. You're looking at a structural grid: columns, beams, slab edges, with daylight or shadow gap between the perimeter of the slab and whatever's stacked above it. At 0.3-0.5 m resolution you can usually count floor lines by the shadow each slab edge throws, especially on a low sun angle pass. The top of the building has an unfinished, stepped look. It's the same silhouette this site's own mark is built around.
Other tells at this stage:
- A tower crane still doing structural lifts, not finish-out trips (harder to call from a single frame, easier across a sequence of quarterly passes where the crane's jib position keeps shifting with the building's height)
- Rebar, formwork, or exposed concrete on the upper floors even if lower floors already have glass
- No consistent window or mullion pattern yet, because the curtain wall hasn't been hung
- A laydown yard still active next to the tower, with material staged in visible pallets or bundles
What shell completion looks like once the envelope closes
Shell completion is when the exterior skin goes on, and the visual signature flips. The thing to watch for is uniformity. Once the curtain wall or precast panels are hung, the facade reads as one consistent material across the whole elevation, glass reading as a flat, reflective band or precast reading as a single tone, instead of the patchwork of bare structure and partial glazing you see mid-rise. Floor edges stop being visible because they're behind skin now. The roofline squares off.
A few other signals worth checking against each other before you call it:
- Rooftop mechanical units (HVAC curbs, cooling towers) starting to appear, since MEP rough-in on upper floors usually tracks close behind the shell
- Window pattern regularity, because once glazing is complete the punched or ribbon window rhythm becomes even floor to floor
- Crane activity, if still present, parked at a fixed position doing interior hoisting rather than structural lifts
- Site work outside the footprint picking up: parking lot subgrade, striping, loading dock aprons, curb cuts, which tend to lag shell completion by one or two quarters rather than lead it
None of these alone is conclusive from a single frame. A reflective roof membrane can look a lot like glazing at low resolution, and a crane sitting idle for one pass doesn't mean the shell is done. What actually resolves it is comparing two or three consecutive quarterly captures of the same parcel. If the floor count stopped climbing and the facade went from patchy to uniform between passes, that's shell completion. If the floor count is still climbing, you're still in vertical.
Why the distinction matters for a comp set
For anyone sizing up delivery timing against a comp set, the gap between "topped out" and "shell complete" is usually the gap between a building that's still three-plus quarters from a leasing push and one that's about to start marketing finished space. Tenant improvement crews mobilize once the envelope is weathertight, not before. If your pipeline read can't tell the two apart, every delivery estimate downstream of it is off by a quarter or two, which is enough to misjudge when a competing building starts pulling prospects out of your own leasing funnel.
Construction Pipeline turns this into a quarterly status read per site across a submarket, so the call doesn't depend on catching the right frame at the right sun angle. If you'd rather get that read than build it frame by frame yourself, take a look at the quarterly construction-stage tracking and see if it covers your submarket.