Every cost figure on this site follows the same documented method. Here is exactly how our numbers are built.
1. National baselines
Each material and project type has a national installed-cost baseline expressed per square foot (or per project), maintained as a range: low, typical, high. Baselines reflect 2026 market pricing for materials, labor, disposal and standard accessories.
2. Roof geometry
Ground-floor footprint is converted to roof surface using pitch factors (flat 1.0 up to very steep 1.55). Complexity — valleys, dormers, penetrations — is why real bids can land outside our ranges.
3. Local cost indexes
Each metro page applies a local index (roughly 0.85 to 1.15) reflecting labor rates, permit costs and storm-driven demand in that market. Indexes are editorial estimates refined over time.
What our numbers are not
They are planning ranges, not quotes. Decking condition, access, code upgrades and contractor backlog all move real prices. Always compare several written estimates before signing.