How Polycam Calculates Exterior Measurements
When you scan a space with Polycam, the measurements you see come from surfaces the scanner can actually see. Exterior measurements sit on the other side of the wall, where the scanner never reached, so they are derived rather than measured. In this article you will learn how exterior dimensions are calculated, what wall thickness Polycam assumes, and how to adjust it when you know the real figure.
The Short Answer
Polycam assumes a wall thickness of 10 cm (about 4 inches) and expands the building footprint outward from the surfaces it measured. This value is fixed. It does not change based on the room, the building, or anything detected during the scan.
- Interior measurements: Measured directly from your scan
- Exterior measurements: Derived by adding the assumed wall thickness
- Assumed wall thickness: 10 cm (about 4 inches), applied uniformly
- Adjustable: Yes, per wall, in the Floorplan Editor
How Polycam Measures a Space
Polycam builds its measurements from the surfaces your device can see during a scan.
When you scan the inside of a building, the visible surfaces are the interior faces of the walls. That is where the mesh ends, and that is what the interior dimensions are based on. Everything beyond the drywall, including the wall cavity, the sheathing, and the exterior cladding, is never captured, because no light from the scan reaches it.
How Exterior Measurements Are Calculated
To produce a building footprint, Polycam takes the measured interior surface and offsets it outward by the assumed wall thickness of 10 cm. The interior dimensions stay exactly as measured, and the exterior boundary is placed 10 cm beyond them.
Is the Estimate Static or Dynamic?
It is static. Polycam applies the same 10 cm assumption to every wall, in every scan. It is not scaled by room size, wall length, building type, or anything inferred from the capture, and it does not vary between one project and the next.
This means the accuracy of an exterior measurement depends entirely on how close the real wall is to 10 cm. A standard interior partition is often close to that figure. An exterior wall with insulation, sheathing, and brick cladding can be considerably thicker, and the footprint will read correspondingly small.
Adjusting Wall Thickness
If you know the real wall thickness for your space, you can change it in the Polycam Floorplan Editor. Thickness is set per wall, so interior partitions and exterior walls can each carry their own value.
- Open your floorplan in the Floorplan Editor.
- Select the wall you want to change. The properties panel opens, showing Type, Thickness, and Length.
- Enter the real thickness in the Thickness fields, which take feet and inches.
- Repeat for any other walls that need a different value, then save your changes.
| Wall type | Typical thickness |
|---|---|
| Interior walls | 4 to 6 inches (about 10 to 15 cm) |
| Exterior walls | 6 to 12 inches (about 15 to 30 cm) |
Frequently Asked Questions
Why does Polycam assume a wall thickness at all?
A scan taken indoors only captures the interior faces of the walls. The thickness of the wall itself is never visible to the scanner, so a value has to be assumed in order to produce a building footprint.
Are my interior measurements affected by this assumption?
No. Interior measurements come directly from your scan. The wall thickness assumption only affects the exterior boundary.
Does the assumed thickness change depending on the space?
No. The same 10 cm value is applied to every wall in every scan.
Can I set a different thickness for individual walls?
Yes. Select a wall in the Floorplan Editor and enter its thickness in the properties panel, so exterior walls and interior partitions can each use their own value. See How to Use the Polycam Floorplan Editor for more on editing walls.
Is there a minimum wall thickness?
Yes. Walls cannot be set thinner than 2 inches (about 5 cm).