The city building department's review of construction plans for code compliance — happens between application submission and permit issuance.
Cities typically request 2-3 rounds of corrections during plan check. Each round adds 2-4 weeks. Specialty plan check may be required for hillside, historic-district, or coastal-zone projects. Hire an architect or designer who has recently permitted in your city — they know the desk reviewers' preferences.
Part of the BackyardADU California ADU Glossary — plain-English definitions of the regulatory, construction, and financing terms you'll encounter during a California ADU project.