Accessory Dwelling Units
Accessory Dwelling Units (ADUs) in Northern Virginia
Design-build ADU construction across the DMV — detached, garage conversions, basement suites, above-garage units, all under one contract.
Schedule your free ADU consultationWhat is an ADU?
An accessory dwelling unit is a smaller, self-contained home on the same lot as a primary residence. A true ADU has the essentials of independent living: a kitchen or kitchenette, a bathroom, a sleeping area, and a way to enter without walking through the main household. Homeowners use different names for the same idea: granny flat, in-law suite, casita, backyard cottage, accessory apartment, basement suite, or garage apartment. The common thread is flexibility. An ADU can support aging parents, adult children, long-term guests, caregivers, or rental income, while letting the owner keep the main home and land they already have.
Types of ADUs we build
Detached new construction
A freestanding backyard cottage with its own kitchen, bathroom, sleeping area, and separate entrance.
Garage conversion
A practical way to turn underused garage space into code-compliant living space while preserving the main home.
Basement / lower-level conversion
A lower-level suite that can work well on sloped Northern Virginia lots with exterior access.
Above-garage units
A compact apartment built over a new or existing garage, often ideal when yard area is limited.
Attached additions / in-law suites
A connected suite that adds privacy for family, guests, or future rental flexibility.
Virginia's new ADU law makes it easier
Virginia SB 531 makes ADUs by-right in single-family zoning effective July 1, 2027. For homeowners, the biggest practical changes are simple: local permit fees are capped at $500, and the family-relation rule is eliminated. That means ADUs move from a limited, locality-by-locality exception into a predictable planning option across Virginia. Details will still matter — building code, setbacks, utility design, stormwater, and site constraints do not disappear — but the legal starting point becomes much stronger for homeowners. Read the full breakdown on our Virginia ADU law explainer.
Our 4-step ADU process
Free consultation
We review your goals, property, budget, timeline, and likely ADU type before you commit to a design path.
Design
Our team prepares plans, 3D renderings, engineering coordination, and a layout that works for the site.
Permits
We handle the entire submission, respond to comments, and coordinate the jurisdictional review process.
Build
A single crew, single contract, and single point of contact carry the project through final inspection.
ADU costs in Northern Virginia
ADU budgets depend on size, structure, utilities, finish level, access, drainage, and locality review requirements. A basement suite can reuse existing walls and roof area, while a detached cottage needs a foundation, envelope, utility runs, and site work. Tight Arlington lots often require more staging and protection. Larger Loudoun parcels may introduce longer driveways, septic, well, or grading questions. These ranges are planning numbers, not fixed bids, but they help homeowners compare ADU types before design begins.
Garage conversion
$80,000–$180,000
Basement suite
$80,000–$200,000
Above-garage addition
$150,000–$280,000
Attached in-law addition
$150,000–$300,000
Detached new construction
$200,000–$450,000+
Ranges depend on size, finishes, site conditions, utility strategy, and locality permit fees.
Why Capital Design Build Group
Licensed and insured for residential design-build work.
Completed ADU and small-dwelling projects across the DMV.
Single-source design-build accountability from feasibility through final inspection.
DMV-based team with an Arlington office close to Northern Virginia permitting agencies.
Frequently asked questions
Can I rent out my ADU?
Yes. SB 531 ends the family-relation rule on July 1, 2027, so the occupant does not have to be related to the homeowner.
How long does it take?
Most ADU projects take 4–9 months to build after design and permits, depending on scope and jurisdictional review.
Do I need separate utilities?
Usually no for attached or basement units. Detached ADUs sometimes need separate or upgraded utility service depending on the site.
Will it raise property taxes?
Almost always yes. An ADU adds usable living area and value, so consult your county assessor for property-specific guidance.
Can my neighbors stop it?
After SB 531 takes effect, ADUs are by-right, so neighbors cannot stop a compliant ADU simply because they object.
Do you handle permits?
Yes. We prepare the permit package, submit it, respond to comments, and coordinate the process end-to-end.
Ready to plan your ADU?
We can evaluate your lot, explain your options, and map a realistic design, permit, and construction path.
Schedule your free ADU consultation