About QuakeRetrofitCheck
Why this exists
"Does my house need an earthquake retrofit" searches mostly turn up either a contractor's sales page or a vague hazard map with no dollar figure attached. QuakeRetrofitCheck instead reports the same Seismic Design Category the building code itself uses, city by city, next to what a retrofit and the California grant that funds part of it actually cost.
What goes into the number
Every city's category, peak ground acceleration and spectral response values come from USGS's own ASCE 7-16 Design Maps web service, queried point by point. Retrofit cost figures are sourced from multiple 2026 contractor-cost guides; California's Earthquake Brace + Bolt grant terms come from the program's own published rules. All three are documented in the methodology guide.
A code category, honestly labeled
A Seismic Design Category describes ground motion at a point, assuming standard occupancy and average soil conditions - it is not an assessment of any one house's actual foundation, age or condition. This site says so on every page and never claims to replace a structural engineer's inspection of a specific property.
Who runs this
QuakeRetrofitCheck is an independently run site. It is not affiliated with USGS, the California Earthquake Authority, or any retrofit contractor or insurer. Where a page includes a sponsored link, that is disclosed on the page itself and in the privacy policy.
Written by
Each city page is generated by AI software from the cited USGS Design Maps data and the published Earthquake Brace + Bolt program rules - no journalist or editor writes or reviews a page before it publishes. The seismic and cost figures themselves come from USGS and the cited cost guides, not from AI; the AI only assembles the sentences around them.