How it works
How we measure a roof without a ladder
Every number comes from airborne LiDAR — laser scans flown over U.S. cities by public agencies. Here is what happens between typing an address and seeing your roof numbers.
1. Finding the building
The address is placed on a satellite map and matched to a building outline from our national footprint database (county, city and Microsoft open building footprints). If the pin lands between buildings, you tap the right roof.
2. Reading the LiDAR
A LiDAR survey records the 3D position of millions of laser returns. We pick the best validated survey covering the property — USGS 3D Elevation Program, NOAA Digital Coast or a state program — and read only the points around that building.
3. Measuring pitch
Points on the roof are grouped into flat planes. The slope of those planes is the roof pitch, reported in the roofer’s format of inches of rise per 12 inches of run (for example 6/12).
4. Roof area and squares
The building outline is multiplied by the slope factor to get roof surface area. Because the outline may miss part of an overhang, the free result also shows a likely range. Divide by 100 for roofing squares; add 10–15% waste for most shingle roofs.
5. The full report in the app
The RoofTap app goes further: it reconstructs every roof facet in 3D, measures each facet’s pitch and area, ridge, hip, valley, eave and rake lengths, and builds a material quote and PDF report.
Limits you should know
- LiDAR is a snapshot from its flight year — new roofs, additions or rebuilt houses may not match.
- Dense trees, very small or very complex roofs can prevent a measurement.
- Estimates are for planning and quoting; verify on site before ordering material.