Streamlined rules proposed for accessory living units

The Fairfax County Planning Commission is considering changes to make it easier for residents to establish accessory living units (ALUs).

The Zoning Ordinance Work Program approved by the Board of Supervisors for fiscal years 2026-27 includes consideration of new standards for ALUs as a first-tier topic. The board’s Land Use Process Review Committee will discuss the issue at its Dec. 4 meeting.

An ALU is defined as “a secondary dwelling unit established in conjunction with and clearly subordinate to a single-family detached dwelling unit.”

An ALU must include separate areas for eating, cooking, sleeping, living, and sanitation. An ALU inside a principal dwelling unit can be approved with an administrative permit. A detached ALU is only allowed on a lot of at least two acres and requires a special permit.

The board authorized ALUs in 2021 as part of a major overhaul of the zoning code. At that time, there was opposition from residents who raised concerns that ALUs would destabilize neighborhoods and turn single-family homes into “boarding houses.”

More housing needed

According to a white paper prepared by planning staff, a total of 366 administrative permits and 41 special permit applications were submitted between July 1, 2021, and Oct. 31, 2025.

A total of 158 ALUs have been approved, although 69 of them were not renewed after the initial two-year approval period.

“This represents a small fraction (0.08 percent) of the number of single-family detached dwellings in the county, which may indicate an opportunity to review zoning regulations to expand opportunities for ALUs,” the white paper states.

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In Mason District, 51 administrative permit applications were submitted in the past four years, but so far, only 16 were approved. One was denied, one is currently in review, six expired, and seven were voided or withdrawn. Twenty are held up while the applicant responds to requests for information from staff, applies for building permits, completes construction, or waits for final inspection.

Three applications for special permits for detached ALUs were submitted in Mason District. One was approved, one was accepted, and one was withdrawn.

Remove obstacles

The white paper presents the following recommendations for updating and streamlining the ALU regulations:

• Align the ALU program with the resolution adopted by the Board of Supervisors in September that identified the provision of attainable housing as a major priority.

“ALUs are one of the many tools that can help create additional housing options for renters, as well as provide supplemental rental income to owners of the principal dwelling,” the document states.

• Clarify and update the regulations to reduce the number of interpretations required about whether an application is for an interior or detached ALU or whether the proposal meets the definition of an ALU.  

• Streamline the process and remove unnecessary impediments to establishing ALUs. For example, allow the use of the entire basement, regardless of when it was constructed.

• Revise the initial approval from two years to five years or consider deleting the renewal requirement.

• Add provisions for a semi-detached ALU, and revise standards for determining whether an ALU is interior, detached, or semi-detached.  

When some homeowners consider renovations and learn that they have to apply for an ALU permit, they modify their building permit application by, for example, proposing a wet bar rather than a kitchen, the document notes. In other cases, applicants for building permits say they’re proposing a second kitchen for entertainment purposes, not for an ALU. Those kinds of issues delay the approval process.

• Consider allowing administrative permits for certain detached ALUs and review the maximum occupancy, owner-occupancy, and parking requirements.

• Streamline the administrative approvals to remove the requirement for a separate ALU permit or incorporate the zoning review as part of the building permit process. When ALUs were first proposed, many residents opposed administrative permits, which don’t require public input.

• Delete the requirement to record the approval in the land records.

• For detached ALUs, reconsider the 1,200-square-foot maximum size, reduce the minimum lot size, and revise the setback requirements.

• Consider allowing an interior ALU in a townhouse.

Planning staff will schedule community meetings to discuss preliminary concepts in early 2026. Draft text would then be developed. The Planning Commission hearings could be held by the end of the year.