Roof EGR produces an educational planning range from a roof measurement, disclosed configuration and homeowner answers. It is not a contractor proposal, appraisal, insurance estimate, certified measurement report or inspection.
Calculation sequence
- Locate the closest building to the submitted address coordinates.
- Accept Google Solar roof data only when required fields, imagery quality and configured area bounds pass validation.
- Otherwise use the manual footprint, stories and pitch path.
- Apply a geometry-based waste factor.
- Apply the selected material’s configured base rate.
- Apply disclosed height, steepness, tear-off, condition and penetration modifiers.
- Add configured disposal and permit allowances and enforce the minimum job floor.
- Apply a wider uncertainty spread to manual sizing than accepted satellite sizing, then round the displayed endpoints.
What is data and what is an assumption?
Address-derived building geometry and imagery quality come from Google Solar. Weighted pitch and complexity are derived from roof segments. Product rates, modifiers, fees, bounds and uncertainty spreads come from the Roof EGR configuration. Homeowner answers supply conditions that imagery cannot verify. A polygon correction is a homeowner-entered measurement.
Known limitations
- The closest detected building may be wrong.
wholeRoofStatsmay not include the entire building.- Trees can obscure edges and roof planes.
- Imagery can predate an addition or garage change.
- Satellite data cannot inspect decking, flashing, ventilation or existing layers.
- Configured pricing is not a live survey of contractor bids.
Why the output is a range
A range makes uncertainty visible. The current configuration uses a narrower spread for accepted satellite sizing and a wider spread for manual sizing. It should narrow only after the roof and scope are verified—not because a marketing page wants a more attractive number.
Data reference: Google Solar API Building Insights. Current estimator configuration reviewed July 20, 2026.