Arlington Basement ADU: The Most Cost-Effective Way to Add a Fully Independent Living Unit

A basement ADU is an accessory dwelling unit created within the lower level of an existing home. Arlington County permits basement ADUs subject to building code requirements for egress, ceiling height, natural light, and habitability. Berriz Design Build evaluates your basement's ADU potential during the initial consultation.

Arlington County requires basement ADUs to meet residential habitability standards: minimum ceiling height (typically 7 feet), egress windows or doors in sleeping areas, adequate natural light and ventilation, separate entrance, kitchen, and bathroom. Berriz Design Build evaluates compliance and addresses deficiencies in the design phase.

Basement ADU conversions in Arlington typically range from $120,000 to $220,000 depending on existing conditions, scope of work, and finish level. This is generally the most cost-effective ADU type. Use our Pricing Guide for current ranges.

Yes. A basement ADU requires building permits covering structural, electrical, plumbing, and mechanical work, plus zoning approval as an ADU. Berriz Design Build prepares and manages all permit applications.

Yes. Arlington County permits basement ADUs to be rented to non-family members, subject to the owner-occupancy requirement for the primary residence. Berriz Design Build designs basement ADUs with rental viability in mind — separate entrance, acoustic separation, and independent utility access where feasible.

36+ years of Arlington basement renovation and ADU experience, in-house design and construction, and a thorough approach to the moisture, egress, acoustic, and design challenges that determine whether a basement ADU becomes a genuine living space or a compliance problem.