Know Before You Buy – Real Estate Questions

Before you invest in a new property, we recommend you thoroughly research the property.

Research Current Property Information

The SF Planning Department keeps records on San Francisco's parcels and properties. Using the Planning Department's San Francisco Property Information Map ( you can look up the Zoning District, Permit History, Case History, Historic Preservation information, and much more for each property in San Francisco.

A History of Building Permits and Records

Generally what establishes legality of a use or a structure is a building permit. The Department of Building Inspection's Records Management Division (RMD) answers general questions from emails and SF 311 Customer Service Center referrals and inquiries. RMD is responsible for storage and reproduction of plans, permit applications, job cards, and miscellaneous documents; producing the Report of Residential Building Records (3R) and maintaining historical records.

The Records Management Division is divided into two sections: Records Management and Report of Residential Building Records (3R). Their offices are located at 1660 Mission Street, 4th Floor, San Francisco, CA 94103. The 3R report provides a summary of building permit history for the property and indicates what the Department of Building Inspection (DBI) considers to be the number of legal dwellings currently on a site.

Assessor-Recorder Office and Existing Usage

The Assessor-Recorder's Office also keeps records of land use. However, these are not always reliable. For example, the Office's records will recognize existing uses without verifying they are legal; often, the record may show a building containing more dwelling units than were created with proper building permits.

Similarly, an approved building permit is definitive as to the legal use on a site rather than the Assessor-Recorder's Office listings. For example, if the Office lists a property as "Industrial" and the last approved building permit for the space in question was for office use, then the use is legally office space.

However, in absence of other records, Assessor records may be helpful in indicating how a property has been used over time. Contact Records Management/3R for guidance when building permit history is ambiguous or lacking.

Determining Legal Use

Please note, realtors will sometimes advertise properties containing "unwarranted" space or "unwarranted dwellings." These dwellings are often "in-law" units, usually a minor unit at the ground floor. The listing of space or units as "unwarranted" indicates that its legality is not verified. Only the building permit history, and the associated 3R report in the case of dwellings, is the evidence for legality.

It is important to verify that dwellings are legal as often they cannot be legalized due to zoning density limitations; additionally, fees and penalties may apply to legalize the space. Further, if tenants occupy illegal units, additional costs may accrue to a new owner in any eviction process required to legalize the occupancy of the space.