Build Your ADU in the City of Fairfax, VA
Makara ADU designs, permits and builds accessory dwelling units to the City of Fairfax’s rules, and builds nothing else.
- ADU max size
- Up to 35% of the main house's floor area · a detached unit also no more than 50% of the house's footprint
- Minimum lot size
- No minimum
- Owner occupancy
- Required
- Off-street parking
- No additional parking required
- Allowed by
- Right, in permitted zones
- Rules current as of
- 2026-09-30
- Licensed & Insured in Virginia (Class A 2705184565)
- City of Fairfax ADU Specialists
- Full-Service: Design → Permits → Build
- Free Property Eligibility Assessment
Can you build an ADU in the City of Fairfax, VA?
City of Fairfax ADU Guidelines
The rules that decide whether, and what, you can build. The table below carries the specifics.
Up to 35% of the main house's floor area
Up to 35% of the main house's floor area · a detached unit also no more than 50% of the house's footprint
Permitted by right
All residential zones. No minimum lot size.
Accessory-Structure Setbacks
Per accessory-structure standards, within the zone's lot and building coverage limits
Off-street spaces
No additional parking required
Owner must live on site
Either the house or the unit must be the owner's primary residence.
Governing ordinance
City of Fairfax City Code §110-3.5.5.D
Check Your Address
Run our free eligibility check and get the City of Fairfax’s rules applied to your exact lot in about a minute.
Check my property →| Requirement | City of Fairfax standard |
|---|---|
| Allowed by | Right, in permitted zones |
| Minimum lot size | No minimum |
| Permitted zones | All residential zones |
| Maximum size | Up to 35% of the main house's floor area · a detached unit also no more than 50% of the house's footprint |
| Setbacks | Per accessory-structure standards, within the zone's lot and building coverage limits |
| Parking | No additional parking required |
| Owner occupancy | Required |
| Garage or basement conversion | Allowed |
| Ordinance | City of Fairfax City Code §110-3.5.5.D |
| Rules current as of | 2026-09-30 |
The City of Fairfax is independent from Fairfax County, so the county's rules, including its two-acre requirement for a detached unit, do not apply inside the city. A detached unit is allowed with the size limited to 35% of the house's floor area and 50% of the house's footprint. An attached ADU is also subject to the 35% of the floor area.
The City of Fairfax ADU Permit Process
Makara ADU handles this entire process from design to move-in, full turn-key.
- 01
Zoning & Eligibility
Confirm the lot has a detached or duplex home, and work out the 35% size limit and, for a detached unit, the footprint and coverage limits. Makara ADU does this free with our property eligibility checker.
- 02
Design & Drawings
Architectural and structural plans to the city's residential code, sized within the 35% limit and the zone's coverage rules.
- 03
Zoning Permit (City)
File the Zoning Permit for Residential Accessory Use and Occupancy with the signed ADU Affidavit at the Zoning Division. Makara ADU handles this for its clients.
- 04
Building Permits & Build
Building and trades permits from the city; construction proceeds with city inspections along the way.
- 05
Final Inspection & Occupancy
The city's final inspection and occupancy approval, then keys in hand, ready to occupy or rent.
City of Fairfax’s ADU Specialists
We don't build everything. We build ADUs. Based in Gaithersburg, we work with local permitting offices every week and know how each jurisdiction's rules shape what can be built.
Local Rules, Known Cold
Every jurisdiction we serve has its own size limits, setbacks, parking and occupancy rules. We track them, and the eligibility checker on this page runs on that same data.
One Contractor, Start to Finish
Architecture, engineering, permits, foundation, framing, MEP, sprinklers, finishes, and the rental license — Makara ADU manages everything under one contract. No coordinating separate architects, engineers, and builders.
Fixed-Price Proposals
We quote your project in full before a shovel goes in the ground. No surprise change orders mid-construction — we plan for lot coverage, stormwater, and utility connections up front.
Built for Aging in Place & Family
Most of our City of Fairfax clients build to keep aging parents or adult children close. We design single-floor, accessible units that work beautifully today and adapt gracefully over time.
ADU Types We Build in the City of Fairfax
Most jurisdictions allow more than one ADU configuration. We help you choose the right one for your lot, your zone and your goals.
Detached Backyard Cottage
A fully independent structure in your backyard with its own entrance, kitchen and bath. The most flexible option, and the one most people picture. Size and placement follow the rules in the table above.
Attached Second Home
Add an attached ADU with its own separate entrance, kitchen, and bath. Makara ADU will collaborate with you to design the space to be functional to meet your needs while creating an aesthetically pleasing space that will add value to your life, family and your home.
Basement and Garage Conversions
Convert an existing garage or basement into a legal, licensed ADU — the most cost-effective path to added living space, and often faster to permit than new construction.
ADUs We’ve Built Recently
A sample of ADUs we’ve built across Northern Virginia.
City of Fairfax ADU FAQ
Can I build a detached ADU in the City of Fairfax?
Yes. The city allows an accessory dwelling unit as a separate, detached structure as well as attached to the house, provided it stays within 35% of the house's gross floor area, 50% of the house's footprint, and the lot's building-coverage limits.
How big can an accessory dwelling unit be?
No more than 35% of the gross floor area of the main house. A detached unit must also be no more than 50% of the house's footprint.
Can I rent out the unit?
Long-term, yes, provided the owner lives in the house or the unit. Short-term rental is not permitted.
Is extra parking required?
No additional parking is required for the unit.
What approval do I need?
A Zoning Permit for Residential Accessory Use and Occupancy with a signed Accessory Dwelling Unit Affidavit, submitted to and approved by the city's Zoning Division, then building permits.
Do Fairfax County's ADU rules apply in the city?
No. The City of Fairfax has its own zoning ordinance and its own accessory dwelling standards.
Is Your City of Fairfax Property Eligible for an ADU?
Use our free eligibility checker to find out in about a minute, and get a personalized report sent to your inbox.