How we know what we know
Where our data actually comes from.
Every number on this site has a paper trail. Permit fees and timelines come from each city's published schedule. Cost benchmarks are calibrated against HCD data and contractor surveys. Statutes are quoted from the California Legislature's bill record. We update quarterly and fast-track corrections.
City data
Permit fees, processing windows, impact-fee policies, and notable local rules are sourced directly from each city's planning department portal. We re-verify every published city quarterly (most recently May 2026). If you spot a stale number, email us — corrections land within 48 hours.
Cost benchmarks
Per-square-foot build costs for the three ADU types (detached, attached, garage conversion) at the three finish tiers (basic, standard, luxe) are calibrated against published HCD data, the AARP ADU Guide, and recent contractor pricing surveys for the LA-area market. They do not include financing costs, landscaping, or furniture. Property value uplift figures (25–35% of lot value) are based on Fannie Mae appraisal guidance and recent comparable-sale data.
2026 law explainers
Statute summaries are plain-language paraphrases of the operative provisions of each cited bill. Citations link to the California Legislature's public bill record. We've focused on bills that materially change the financial or procedural calculus for a typical homeowner — not exhaustive coverage of every ADU-adjacent enactment.
What we don't independently verify
We do not perform site visits, lot surveys, or feasibility analyses. We do not have access to the inside of any given city's plan-check queue or staff. The dossiers describe the system's published rules; your project's actual experience will depend on the people, the lot, and the timing.