Accessory Dwelling Units in Great Falls, VA

Accessory Dwelling Units in Great Falls, VA: Expanding Estates with Purpose

Great Falls, VA—with its expansive lots, serene surroundings, and emphasis on privacy—offers ideal conditions for adding Accessory Living Units (ALUs). Unlike denser neighborhoods, these spacious properties allow for custom detached units that suit multigenerational living, staff quarters, or private guest retreats, all without compromising the estate’s character.

What You Can Build: ADU Regulations in Great Falls (Fairfax County)？

While Great Falls has no separate zoning code, it adheres to Fairfax County’s ADU regulations, which accommodate the area’s larger lot sizes:

Regulation Category	Rule Summary
Eligibility	ADUs allowed only on single-family detached homes.
Size Restrictions	Interior ADUs: ≤800 sq ft or 40% of main dwelling; Detached: ≤1,200 sq ft if lot ≥2 acres.
Occupancy	Max. 2 persons; owner must reside on property.
Parking	One extra on-site space required (in addition to standard requirements).

ADU Permitting: What Great Falls Residents Need to Know

Depending on the type of ADU, the approval process varies:

• Interior ADUs: Submit through Fairfax County’s PLUS system for an administrative permit.

• Detached ADUs: Require a special permit. Site plans, setbacks, and architectural harmony with the main dwelling are closely reviewed.

Tip: Great Falls residents often have HOA covenants or private road agreements—check these early in the planning process.

What Does It Cost?

Construction costs vary based on design complexity and finishes, but here are general estimates:

Type of ADU	Estimated Cost per Sq Ft
Interior Conversion	$275–$325
Detached Construction	$325–$400

On a two-acre property, a 1,200 sq ft detached ADU could range from $390,000 to $480,000, depending on customization.

For a detailed overview, refer to our Fairfax County ADU guide.