ADUs for Income in Fairfax City: What’s Allowed

Thinking about building an accessory dwelling unit to help offset your mortgage in Fairfax City? You are not alone. Many homeowners want extra space for family or a potential tenant and hope the rent can pencil out. In this guide, you will learn exactly what Fairfax City allows, what it takes to get a permit, and the realistic income scenarios to consider. Let’s dive in.

What Fairfax City allows today

Fairfax City permits ADUs only when they are part of the main single-family home. Detached backyard cottages are not allowed. Any new exterior entrance must be on the side or rear of the house. You can review the City’s official ADU standards in the Accessory Dwelling Unit packet from the Zoning Division.

• Location: ADU must be inside or attached to the principal dwelling. New entrances must face the side or rear. See the City’s ADU packet.
• Size: The ADU’s gross floor area cannot exceed 35 percent of the main dwelling’s gross floor area.
• Bedrooms: Maximum of two bedrooms.
• Parking: ADU occupants may use no more than two vehicles.
• Occupancy: One of the two dwellings must be owner occupied, and at least one of the two dwellings must be occupied by a person who is 55+ or a person with a disability. The combined occupancy must also meet the City’s “one family” definition.

Can you use an ADU for income?

Short answer: it is possible, but not as an open market rental. The owner-occupancy requirement and the 55+ or disabled occupant requirement limit who you can rent to. Read the City’s occupancy rules closely before you count on market-rate rent.

Long-term rental scenarios that can work

If you want to collect rent, here is a compliant setup to consider:

• You live in the main home, and the ADU tenant is 55+ or a person with a disability.
• The total household meets the City’s “one family” standard.
• The ADU follows size, bedroom, and parking limits.

Review the official standards in the City’s ADU packet to confirm your plan.

What about short-term rentals?

Using an ADU for short-term stays is unlikely to fit the City’s ADU rules. Fairfax City also regulates lodging separately. For context on how Northern Virginia handles short-term lodging permits and taxes, see Fairfax County’s overview of short-term lodging rules and taxes. Always verify current City of Fairfax requirements with the Zoning Division before hosting.

How to get approved

Here is a simple path to move from idea to approved ADU:

1. Start with zoning. Open the City’s Zoning page and Permit Portal to access the ADU application and affidavit. Submit floor plans and required forms. Go to the Zoning page.
2. Pull building and trade permits. If you add or change structure, electrical, mechanical, or plumbing, you will need permits under the Virginia Uniform Statewide Building Code. Review USBC basics on use and egress in the state code reference here.
3. Schedule inspections. The City will inspect the ADU for zoning compliance. Building inspections will verify code work.
4. Record conditions. Keep a copy of the approval and occupancy conditions. If conditions change, the ADU use may need to stop and the space be reintegrated into the main home.
5. Keep contact handy. City of Fairfax Zoning Division: 703-385-7820 or [email protected].

Design and code tips to plan early

• Plan for safe egress and alarms. The USBC includes requirements for exits and smoke/CO detection. Confirm details during permit design.
• Place the entrance carefully. New exterior doors must face the side or rear of the house.
• Keep size in check. Cap the ADU at 35 percent of the main home’s floor area, with no more than two bedrooms.
• Think about accessibility. Since at least one occupant must be 55+ or a person with a disability, simple features like fewer steps, good lighting, and wider doorways can improve livability.
• Manage parking. ADU occupants are limited to two vehicles. Make a realistic parking plan.

Financing, taxes, and insurance

• Mortgage qualification: Some loan programs may count ADU rent for underwriting if the ADU use is legal and documented. Because Fairfax City limits who can rent the ADU, lenders may require proof that your planned tenant profile is allowed. Learn more about how lenders view ADU income from recent program updates here. Always verify with your lender and a local appraiser.
• Taxes and licensing: Long-term rent is taxable. Short-term rentals can trigger transient occupancy taxes and local business rules. See a regional example of STR tax and permit requirements in Fairfax County’s short-term lodging page, then confirm City of Fairfax specifics with the City finance office.
• Insurance: Tell your insurer about the ADU and any tenant. You may need a landlord endorsement or specialized coverage for short-term stays.

HOAs, resale, and enforcement

• HOA and deed rules: Private covenants can prohibit ADUs or rentals even if the City approves them. Always confirm HOA and deed restrictions before you apply.
• Resale: The ADU cannot be sold separately from the main home. When a property transfers, the new owner must certify whether ADU use will continue.
• Enforcement: The City can inspect on complaint or at renewal. If occupancy no longer meets the approval conditions, you must cease the ADU use and fold the space back into the main dwelling. Details are in the ADU packet.

Watch for state-level changes

Virginia lawmakers have considered bills that would expand ADU rights statewide, including detached ADUs and limits on owner-occupancy rules. Track a recent example, SB 304, on the General Assembly tracker at LegiScan. If state law changes, Fairfax City may update its ordinance, so check for updates before you design or finance a project.

Key takeaways

• Detached ADUs are not allowed in Fairfax City. Interior or attached only.
• Income is possible, but only within the City’s occupancy limits, including owner occupancy and a 55+ or disabled occupant in one of the two dwellings.
• Permits matter. You need zoning approval and any building or trade permits under the USBC.
• Plan ahead. Confirm HOA rules, lender treatment of ADU income, and insurance before you build.

If you want help thinking through an ADU in the City of Fairfax or exploring properties that already have compliant space, reach out to Rich Asumadu. You will get clear guidance and options that fit your goals.

FAQs

Can I build a detached ADU in Fairfax City?

• No. The City’s ADU must be within or attached to the main single-family home. Detached backyard cottages are not allowed under current rules.

Who can live in a Fairfax City ADU if I want rental income?

• One dwelling must be owner occupied, and at least one of the two dwellings must be occupied by a person who is 55+ or a person with a disability. The total household must meet the City’s “one family” definition.

Are short-term rentals allowed in an ADU?

• The ADU rules and occupancy conditions make short-term hosting difficult to comply with. Check the City’s zoning and lodging rules before listing any space.

What are the first steps to get an ADU approved?

• Review the City’s ADU packet, apply through the Permit Portal, secure any required building and trade permits, schedule inspections, and confirm HOA, lender, and insurance requirements.

Can lenders count ADU rent in mortgage approval?

• Some programs will count ADU income if it is legal and documented. Because Fairfax City limits who can rent the ADU, confirm acceptability with your lender and appraiser before relying on projected rent.