Baseline Mansionization Ordinance

The following information relates to the Baseline Mansionization Ordinance, the Baseline Hillside Ordinance and the R1 Variation Zones adopted in March 2017 the relate to the restrictions on residential building in our area. See below in RED for a summary of what this all means.

On March 17, 2017 the following Neighborhood Conservation Initiatives went into effect:

Baseline Mansionization Ordinance Code Amendment (CF 14-0656) that modifies Single-Family Zones (RA, RE, RS, R1).

Baseline Hillside Ordinance Code Amendment (CF 14-0656) that modifies Single-Family Zone Hillside Area Regulations.

R1 Variation Zones and Rear Detached Garage Supplemental Use District (SUD) Code  Amendment (CF 16-1460) that adds more tailored subsets of the R1 Zone and a Rear Detached Garage SUD to the Code, and

Neighborhood Conservation Zone Changes (CF 16-1470) that applies the R1 Variation Zones and/or Rear Detached Garage SUD to a number of single-family neighborhoods.
Please click the links below for copies of the Ordinances, including the maps related to neighborhoods that have been re-zoned to an R1 Variation Zone and/or Rear Detached Garage Supplemental Use District.
  • Modifications to Single-Family Zones (RA, RE, RS, R1) and Single-Family Zone Hillside Area Regulations, R1 Variation Zones, and Rear Detached Garage Supplemental Use District, Ordinance No. 184,802

Summary of the BMO, BHO and R1 Variation Zones Outlined in the link above.

City Planning has focused their attention as dictated by a direction from the LA City Council, so the major change effect smaller "R1" zoned lots under 10,000 square feet. Those with larger lots will feel little impact from the changes. Changes from the previous rules include:

- a reduction in livable building allowance from 50% of the lot size to 45% of the lot size.
- elimination of the 20% bonuses for certain architectural characteristics
- elimination of half of the garage exemption (now 200 sf does not count toward total building size instead of 400 sf before)

If you imagine a typical 7,500 square foot lot, under the previous BMO, one would have been allowed to build a home 4,500 square feet. Now, on that same lot, the total home size would be about 3,575 square feet. In both cases, basements are currently unlimited as they do not count toward total square footage.


In 2008, after a groundswell of homeowners complained about “McMansions,” homes that were too large and out of character for their neighborhood, the City passed the Baseline Mansionization Ordinance (BMO) and its sister, the Baseline Hillside Ordinance (BHO).  The intent of the new rules was to put limits on the size of new home construction, and encourage design with more character.  In other words, less big boxes.

The new building parameters had a positive effect in some neighborhoods, where the limits and bonuses encouraged less intrusive design and construction.  Unfortunately, as demand for new homes increased and builders got wise to the loopholes in the BMO, a significant number of homeowners complained to their council reps that the new homes were still too big.

In 2014, after encouragement from various homeowner associations, Councilman Paul Koretz introduced a motion to further reduce and restrict the BMO parameters, and close the loopholes used by builders to continue the large scale building.  Since the amendments would likely take City Planning more than a year to draft and approve, over fifteen neighborhood associations petitioned the City Council to pass an Interim Control Ordinance, which would temporarily restrict the most egregious aspects of new home construction in their particular area.

Builders and real estate professionals in several areas have already started to push back and are seeking an R1 Variation from City Planning which would allow for construction of larger homes than under the new BMO and BHO. The BHA will continue to monitor the situation and have an open and transparent discussion about the prevalent issues. 

For those thirsty for information on this subject, several areas outside of Brentwood adopted ordinances more specific to their respective neighborhoods. Brentwood did not have a consensus, so we did not pursue an interim solution, choosing rather to work toward the more substantive area zoning variation zones.