Roof EGR uses Google Solar building data to estimate pitch-adjusted roof surface and segment geometry, then lets the homeowner correct the footprint when imagery misses a garage, addition or obscured edge. The result is a planning measurement, not a certified roof report or on-site measurement.
The four kinds of information in an estimate
| Kind | Examples | How to treat it |
|---|---|---|
| Measured | Google-reported roof area, segment area and pitch | Useful when the correct building and complete roof are detected |
| Derived | Weighted pitch bucket, geometry complexity and adjusted order area | Calculated from measured geometry and disclosed rules |
| Homeowner-corrected | Polygon area added or replaced after reviewing the property image | Better than knowingly incomplete imagery, but dependent on the outline drawn |
| Assumed | Default layers, access, deck allowance or unknown penetrations | Confirm during inspection and quote review |
What Google Solar provides
Google documents that its Building Insights endpoint returns building and roof-segment information, including segment pitch and imagery quality. Google also cautions that wholeRoofStats may not include the entire building and that some unassigned roof-area estimates are less reliable. Roof EGR therefore treats imagery quality and completeness as decision signals, not guarantees.
Primary source: Google Solar API: buildingInsights.findClosest.
Why tree cover and additions matter in East Grand Rapids
A canopy can hide roof edges in aerial imagery. Detached garages can also be associated with a different detected building, and newer additions may not appear in the imagery vintage used by the data source. Check the displayed outline against what you know is physically connected to the project. If an entire roof plane or structure is missing, use the polygon correction rather than accepting a precise-looking but incomplete number.
How pitch and waste are handled
When Google supplies roof-surface area and segment pitches, Roof EGR does not apply a second geometric pitch multiplier. For a manual fallback based on a ground footprint, it does apply a pitch factor because sloped surface area is larger than its horizontal footprint. Waste is separate: it represents ordering and cutting allowance, with the current configuration using different factors for simple, moderate and cut-up geometry.
When to request an on-site measurement
- The displayed building is not your home.
- Dense tree cover hides a meaningful roof edge.
- A detached garage or addition is part of the project but absent.
- The roof has low-slope sections, unusual curved geometry or multiple structures.
- You need a binding proposal, insurance document or material order.