Chapter 3.2
Development Densities

• ALL
• Remove Code Barriers
• Create Incentives
• Fill Regulatory Gaps

Maximum Size of Single-Family Residences

INTRODUCTION

The average house size in the U.S. has increased by more than seven hundred square feet since 1973.[1] While large homes may be beneficial to or desired by individual owners, they shift costs to the public and local government. Older, smaller homes may be demolished and replaced with larger homes that disturb the character of the neighborhood.[2] Large homes also produce more greenhouse gas (GHG) emissions, which contribute to climate change.[3] Municipalities can implement ordinances that set a limit on the size of single-family homes to mitigate these harmful effects. Typically, these ordinances seek to limit the spread of “McMansions.” McMansions are large houses in suburban neighborhoods that are regarded as oversized in relation to the character of the neighborhood.[4]

Ordinances setting a maximum house size typically regulate the maximum floor area ratio (FAR), which is the portion of the lot that may be covered by a structure. A municipality may also limit the maximum height, number of stories, or total square feet of the house. Setback and minimum yard requirements can also be used to limit how much of a lot may be covered by the house. Some municipalities have varied height restrictions within the lot. For instance, a two-story structure may be allowed at the rear of the lot, whereas only single-story buildings can be constructed near the public right of way.

A municipality can further tailor the requirements based on individual neighborhoods, rather than residential zones as a whole. For example, if a neighborhood has always had larger homes, new large homes could continue to be permitted. However, neighborhoods with smaller homes could have a more restrictive size limit that would help retain the character of the neighborhood and provide many of the economic and environmental benefits discussed below. In this way, developers can still replace old homes, but only if the new home does not increase the impact on the community and environment.

One potential criticism of these ordinances is that they keep certain people and uses out of certain neighborhoods. However, these ordinances are limiting maximum home size, as opposed to minimum home size, which can make some areas exclusive. Limiting maximum home sizes prevents intrusively large homes in neighborhoods that are occupied by more moderate homes and by people with more moderate means, thereby protecting middle and lower income property owners.

EFFECTS

An ordinance limiting the maximum size of single-family homes may have a dramatic impact on a municipality’s GHG emissions. Residential homes are responsible for GHG emissions related to the demand for heating, cooling, electricity, and water supply, among other things.[5] These demands are met by burning fossil fuels to produce and transport utilities to the house.[6] On average, a typical 2,598 square foot house is responsible for about twenty eight thousand pounds of carbon dioxide emissions each year.[7] In contrast, a “tiny home” of 186 square feet requires an average of two thousand pounds of carbon dioxide each year.[8] As house size increases so too does the output of GHG emissions. If a municipality limits how large houses can be, it also limits how much GHGs are emitted.

Larger homes also require more energy and materials to construct than more moderately sized homes.[9] Construction produces GHGs in four areas: “manufacture and transportation of building materials; energy consumption of construction equipment; energy consumption for processing materials; and disposal of construction waste.”[10] Limiting the maximum size of single-family homes may help reduce the construction sector’s impact on climate change by reducing GHGs in any and all four of these areas.

This ordinance can also help insure the preservation of historic districts and increase affordable housing options. Often builders merge two adjacent properties and demolish the existing structures in favor of one new, much larger structure.[11] In historic districts, this process replaces culturally valuable old homes with large, new homes that disturb the character of the district. In other residential districts, smaller, more affordable homes are replaced with larger homes that low-income populations cannot afford. Municipalities should keep these effects in mind when considering ordinances that limit house sizes.

EXAMPLES

Los Angeles, CA

In 2017, Los Angeles revised its zoning ordinance and FAR calculations to combat the rise of McMansions.[12] The 2017 ordinance changed the way that the FAR is calculated in residential zones. Any portion of a building with a ceiling height of fourteen feet or higher counts as twice the square footage of that area in the FAR calculation.[13] This has the effect of encouraging owners to build houses with more usable space, or in the alternative, sacrifice overall size in favor of high ceilings. The City also now regulates the size of new residential buildings based on the character of existing houses in residential zones. For example, one residential zone allows for a larger building mass only at the front of the lot, while another allows for larger mass only at the rear of the lot.[14] These ordinances insure that an owner will not buy an older, smaller house on a less expensive lot with the goal of demolishing that house and building a McMansion that occupies nearly the whole lot. Combined, these ordinances help limit the availability of McMansions and their impact on neighborhoods and the environment.

To view the provisions, see Los Angeles, CA, Municipal Code § 12.08 (C) (5) (2017).

Austin, TX

Austin, similar to Los Angeles, faced an issue with the spread of McMansions. In order to protect its citizens and neighborhoods from more McMansion-like development, the City implemented “Residential Design and Compatibility Standards,” which regulate the size of houses in certain districts of the City.[15] New developments in these areas are subject to a FAR ratio of 0.4 square feet of building to 1.0 square feet of lot size.[16] Alternatively, if that calculation returns a FAR that would only allow a building smaller than 2,300 square feet to be constructed, then the City does not apply the .4 / 1.0 FAR and allows the developer to construct a 2,300 square foot building.[17] Further, the City limits building height to a maximum of thirty-two feet.[18]

The ordinances also set forth unique setback requirements that insure no new building can be substantially larger than the others. For the front yard, the new building must be setback as far as other provisions of the Code allow, or alternatively, as far as the average setback of at least four other buildings on the same side of the street.[19] This promotes uniformity in the aesthetic of the neighborhood and prevents new buildings from occupying the entire lot with a McMansion-like structure. The City also establishes “setback planes.”[20] These planes are a line beyond which no structure may extend. In general, a line extends 15 feet straight up from lot line and then slants toward the center of the property at a 45-degree angle.[21] This prevents new buildings from encroaching on neighboring properties even if they meet the setback requirements at ground level.

To view the provisions, see Austin, TX, Code of Ordinances, tit. 25, subchapter F, §§ 2.1–2.7 (2006).

ADDITIONAL EXAMPLES

Ashland, OR, Land Use Ordinance § 18.2.5.070 (current through Nov. 2017) (limiting new residences in historic districts to a height of thirty feet and restricting FAR ratios to minimize development impact).

Newport, RI, Code of Ordinances § 17.020.050 (2000) (preventing buildings from covering more than twenty percent of a lot).

Santa Monica, CA, Municipal Code § 9.07.030 (B) (2018), Ord. No. 2572CCS (2018) (limiting lot coverage of a two-story house to thirty five percent for the first story, and twenty percent for the second story).

Palo Alto, CA, Municipal Code § 18.12.040 (2007) (limiting maximum house size to 6,000 square feet).

Atherton, CA, Municipal Code §§ 17.32.040, 17.33.040 (current through Sept. 20, 2017) (setting the maximum dwelling size at eighteen percent of the lot size for lots over one acre in size).