Everything homeowners ask about building an ADU in Alexandria — answered with 2026 data.
Yes, ADUs are allowed in Single-family residential (non-historic) in Alexandria, VA. The maximum size for a detached ADU is 900 sq ft. Attached ADUs can be up to 750 sq ft. Alexandria has an ADU-friendliness score of 6/10. Check our full Alexandria ADU rules page for complete zoning details.
ADU construction in Alexandria typically costs $160,000-$320,000. The cost per square foot averages $180-$360. Garage conversions are more affordable at $85,000-$190,000, while prefab ADUs cost $125,000-$280,000. Permit fees add $3,200-$5,000 to your budget. See our detailed Alexandria ADU cost guide.
Detached ADUs in Alexandria can be up to 900 sq ft. Attached ADUs are limited to 750 sq ft. Junior ADUs (JADUs) have a cap of Not allowed. Maximum height is 20 ft (or height of main house, whichever is less). You are allowed up to 1 ADU per lot on a qualifying lot.
Rear setback: 1 ft minimum; 3 ft if windows face property line. Side setback: 1 ft minimum; 3 ft if windows face property line. Front setback: 20 feet. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 space per unit. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Alexandria is typically 70-100 days. The plan check process takes approximately 3-4 weeks. Pre-approved plans availability: Limited availability.
Average ADU rental income in Alexandria: 1-bedroom units rent for $1,650-$2,150/mo/month, 2-bedroom units for $2,050-$2,900/mo/month. Short-term rentals: Not permitted. Expected ROI: 5-7% annual return.
The minimum lot size for an ADU in Alexandria is 4,500 sq ft. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Alexandria, a garage conversion typically costs $85,000-$190,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.