Outlaw In-Laws, Part 2
by Don Dunning, ABR, CRB, CRS
DRE Lic. #00768985
Originally appeared in Hills Publications, December 6, 1996

Buying a home with an in-law unit may entail not-so-obvious risks to both the buyer and the seller. It is important for you to understand what it takes to have a legal secondary unit.

In order to determine requirements by the City of Oakland, I visited the Zoning, Building and Inspection Departments. From our conversations and the printed material they provided, it became apparent that establishing the status of a secondary unit is a complicated matter.

Grandfathered units

Under certain conditions, an existing unit can be “made legal” even though it may not conform to today’s zoning law. You must be able to document that it was built prior to certain key dates.

Logistical specifications

In order for a home to qualify for a secondary unit, it must be built on a lot not less than 5000 square feet with a width of at least 45 feet. The unit itself must have a “floor area” between 275 and 750 square feet. In addition, it “...will not involve an increase of more than ten percent beyond the building’s existing floor area.”

This “ten percent rule” applies only to “expanding the existing footprint” of the house in order to create a secondary unit. For example, if you have a 1500 square foot split level home, the maximum you can add to the outside of the existing structure for the purpose of developing a secondary unit is 150 square feet. You can then take a portion of the original structure to meet the minimum 275 square feet required for a secondary unit.

The unit must be within, or attached to, the house. It cannot be outside the structure, e.g., a detached garage converted into an “apartment” is not considered legal. 

Bedrooms must have more than one exit, at least one working window and a ceiling height of at least 7’6". 

Two off street parking spaces are required for a single family residence. An additional off street parking spot would be mandated for a second unit.

Depending on when it was completed, a Certificate of Occupancy for the home may be needed.

The owner must occupy one of the units and the secondary unit cannot be sold separately.

The secondary unit must be “clearly subordinate to the primary one-family dwelling unit in size, location and appearance.”


There are several reasons why someone may want to avoid the process. In Oakland, applying for a conditional use permit is a non-refundable $1356. There is also a waiting period of about two months before the application is reviewed. Just knowing that neighbors may register official objections may stop a homeowner from applying.

Some individuals are reluctant to have city inspectors review and approve all the work done to create a secondary unit. Permit procedures can be time consuming and expensive. When work is done without permits, however, there is nothing to prove it was completed properly and to code. This could present health and/or safety problems, and is a major reason why illegal in-laws can pose serious risks. 

3-R reports

The “Report of Residential Housing Record” is the City of Oakland document which indicates whether or not Oakland considers the unit legal. This report is a necessity for any property that has more than one kitchen. Besides pointing out the requirements noted above, a buyer’s agent should recommend that the buyer insist on written approval of the 3-R Report as a condition of the purchase contract.

 A word of caution: the mere existence of a 3-R Report does not necessarily indicate the city approves the secondary unit. It only substantiates that a report has been ordered. It must be read carefully. If the city has approved the secondary unit, it will be clearly spelled out on the bottom portion of the form. 


In-laws go by other names: granny flat, au pair, studio, guest quarters, potential in-law, rental potential. Regardless of what it is called, it is not a legal secondary unit unless the seller can document approval by local authorities. 

Final thoughts

A secondary unit, if properly constructed and legal, can add value to a property. Conversely, a poorly built, illegal unit could be considered a detriment. 

Anyone who buys a home with an illegal unit is also buying the potential problems associated with it. Not all agents, and few buyers, understand what this means. Having a competent, professional agent can be the difference between a positive or heart-wrenching experience. Take the process seriously and do your homework. Don’t let an in-law turn you into an outlaw.

Related Articles:Outlaw In-Laws, Part 1;What Is A Bedroom?, How Important Are Permits?; Buyers’ Do’s and Don’ts, Part I and Part 2; Sellers’ Do’s and Don’ts, Part 1 and Part 2; and How To Interview Agents, Part 1, Part 2, Part 3, and Part 4

Don Dunning has been a full-time, licensed real estate agent since 1979 and a broker since 1982 and is past president of the Oakland Association of Realtors. He provides sales and hourly listing or consulting services with Wells & Bennett Realtors in Oakland and is an expert witness in real estate matters. Call him at (510) 485-7239, or e-mail him at , to put his knowledge and experience to work for you.


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