Local Permitting Guide
Building an Accessory Dwelling in the City of Falls Church
⚠ Important Notice
This page summarizes publicly available government information for general educational purposes only. HomeSprout LLC did not create this information, does not guarantee its accuracy, completeness, or currency, and is not responsible for decisions made based on it. Rules change and vary by property — always verify current requirements directly with the official sources below before proceeding with a project.
Official sources: City of Falls Church — Accessory Dwelling Approval and Permitting Process, Accessory Dwelling Zoning Code Amendment
Does This Guide Apply to You?
This guide applies to the City of Falls Church — an independent city, entirely separate from Fairfax County, despite Fairfax County having its own unincorporated area that's also commonly called "Falls Church" for mailing purposes. If your address says "Falls Church" but you're actually in unincorporated Fairfax County, confirm your jurisdiction first — see our Fairfax County guide if that's you.
One more naming note: the City also runs a separate "Affordable Dwelling Unit" program (income-restricted for-sale/for-rent housing) that also uses the abbreviation "ADU." This guide is about Accessory Dwellings (ADs) — a second unit on your own property — which is a completely different thing.
Falls Church City Council significantly updated its Accessory Dwelling (AD) regulations on April 14, 2025 — most notably, allowing detached ADs for the first time and removing the special-use-permit requirement for most properties. Here's a plain-language summary — for project-specific eligibility, always confirm directly with the City's Zoning Division.
Eligible Zones
ADs are permitted in the R-1A, R-1B, and R-M zoning districts. In the R-M district specifically, only internal ADs are permitted, and only through a Special Use Permit from the Board of Zoning Appeals.
Size Limits
- If the principal dwelling's gross floor area is 1,400 sq ft or more: the AD may not exceed 1,000 sq ft or 50% of the principal dwelling's floor area, whichever is less
- If the principal dwelling's gross floor area is less than 1,400 sq ft: the AD may not exceed 700 sq ft
Setbacks
- Detached ADs up to 15 ft or 1 story in height: 8 ft setback from rear and side lot lines (unless the Board of Zoning Appeals grants a Special Use Permit for less)
- All other ADs: at least 10 ft setback from rear and side lot lines
Occupancy & Ownership
- No more than 4 persons may occupy the AD
- The property owner must use either the main dwelling or the AD as their primary residence at the time the permit and Certificate of Occupancy are issued
- An exception applies for new construction where the main house and AD are built together
- Existing accessory units that don't meet the new standards can seek a one-time grandfathering Special Use Permit from the Board of Zoning Appeals
Permit Process
ADs meeting the standard requirements can go through an administrative building permit rather than a full public-hearing process, followed by review from Building Safety, Public Works, and Urban Forestry before final approval and a Certificate of Occupancy.
Not sure what applies to your property?
Zoning district and lot specifics affect what's actually buildable. We handle the zoning determination and permitting process as part of our design-build service.
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