ADU Cost Guide
ADU Cost in Maryland: 2026 Pricing Guide
What does it really cost to build an accessory dwelling unit in Maryland? Here’s a straight answer by ADU type, plus what actually moves the price up or down.
Maryland ADU construction costs vary widely by ADU type, size, and finish level — but most Anne Arundel County projects fall in a predictable range once you know which type you’re building. Below is a realistic starting-point breakdown; every project gets a firm number after a free, on-site consultation.
Pricing By ADU Type
What Does an ADU Cost in Maryland?
Garage Conversion ADU
$90,000 – $150,000
The fastest, lowest-cost path to a livable ADU — you are reusing an existing structure and foundation.
Attic Conversion ADU
$100,000 – $160,000
Makes use of space you already have; cost depends on ceiling height, insulation, and egress requirements.
Basement Conversion ADU
$80,000 – $140,000
Often the lightest permitting lift of any ADU type, especially with an existing walk-out or egress window.
Detached ADU
$150,000 – $300,000+
A fully separate backyard structure — the most flexible option and the most popular new-construction ADU in Maryland.
What Affects Your ADU Cost
- ADU type & square footage — detached new construction costs more per project but often less per square foot than a conversion.
- Site prep & utility hookups — sewer, water, and electrical runs to a detached structure add cost a conversion usually avoids.
- Foundation type — slab, crawlspace, or full foundation each price differently.
- Finish level — builder-grade vs. custom finishes on kitchens, baths, and flooring.
- Permitting & impact fees — Anne Arundel County’s ADU ordinance (Bill 6-23) and Maryland’s statewide ADU Act set the permitting path; fees vary by jurisdiction and ADU size.
- Existing structure condition — for garage, attic, or basement conversions, the starting condition of that space affects how much rework is needed.
How Your ADU Budget Breaks Down
Across most Maryland ADU projects, the budget splits roughly like this:
- Hard costs (70–80% of budget): materials and labor — framing, roofing, electrical, plumbing, HVAC, and finishes.
- Soft costs (20–30% of budget): permits, design and engineering, project management, and inspection fees.
Knowing that split matters when you’re comparing quotes: a bid that looks lower may be excluding soft costs you’ll still have to pay separately once permitting starts.
Is an ADU a Good Investment in Maryland?
Beyond the immediate build cost, an ADU typically pays back in two ways: added home value and rental or multigenerational-housing income. Industry data on ADU projects generally shows a property value increase in the 10–30% range, with owners who later sell recovering roughly half to three-quarters of construction cost in that added value — on top of any rental income collected while they owned the home. Actual return depends heavily on your neighborhood, ADU type, and rental demand in your specific Anne Arundel County market, so treat these as directional, not a guarantee.
Maryland ADU Permitting & Fees
Permitting is part of the cost equation, not separate from it. Maryland’s statewide ADU Act (SB 891 / HB 1466, effective October 1, 2025) requires counties to allow ADUs by right, and Anne Arundel County’s own ordinance (Bill 6-23) has required local ADU permits since 2023 — ahead of the state law. For the full breakdown of what each law requires, see our complete guide to Maryland ADU law and Anne Arundel’s Bill 6-23.
ADU Cost Questions
How much does it cost to build an ADU in Maryland?
Most Maryland ADU projects run $80,000 to $300,000+ depending on type. Conversions (garage, attic, basement) are typically the least expensive since they reuse an existing structure and foundation; detached new-construction ADUs cost more but offer the most flexibility.
Is an ADU cheaper than a home addition?
Often yes, especially for garage, attic, or basement conversions, since you are not building new foundation or exterior walls. A detached ADU can cost more than a comparable addition but adds a fully separate living space and, in many cases, rental income potential.
Do ADUs need permits in Anne Arundel County?
Yes. Anne Arundel County has required ADU permits since its 2023 ordinance (Bill 6-23), and Maryland’s statewide ADU Act (effective October 1, 2025) sets additional by-right permitting standards. See our Maryland ADU law guide for details.
Get Your Maryland ADU Cost Estimate
Every Anne Arundel County ADU project starts with a free, on-site consultation and a real number — not a lowball teaser quote. We build detached ADUs, garage conversions, attic conversions, basement conversions, and in-law suites across Annapolis, Glen Burnie, Pasadena, Severna Park, Crofton, and Odenton.