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ADU Construction · Montgomery County, Maryland
Permit required
In Maryland, a ADU Construction requires a building permit.
An accessory dwelling unit (ADU) always requires a building permit because it adds a habitable dwelling, including electrical, plumbing, mechanical permits and egress/zoning review. Plans are reviewed under the Statewide + local code (IRC 2021); apply through Montgomery County Department of Permitting Services before work begins.
Source: Statewide + local, IRC 2021 · Verified 2026 by StateDataIndex
Building an Accessory Dwelling Unit requires complex zoning, structural, and utility permits.
As one of the more densely populated areas in Maryland, Montgomery County (around 1,065,949 residents) tends to see higher application volumes at its building department, so it helps to prepare your documentation in advance.
Code Compliance & Inspections
Work on your ADU Construction in Montgomery County will be inspected to ensure full compliance with the current Maryland Building Performance Standards.
HOA & Historic District Approvals
In highly urbanized counties like Montgomery County, municipal bureaucracy is only the first step. You will almost certainly need written approval from your Homeowners Association (HOA) before applying for a city permit. Additionally, if you live in a designated historic district, the local architectural committee holds veto power over your ADU Construction.
Zoning & Cost Factors
Maryland integrates local zoning with state-level "Smart Growth" initiatives, heavily restricting sprawl and protecting the Chesapeake Bay watershed. Fortunately, Maryland maintains relatively builder-friendly regulations, keeping base permit fees competitive.
Permit fees in Montgomery County
Permit fees vary by jurisdiction and by your project's valuation, so there is no single fixed figure for Montgomery County. We only publish fees confirmed by real homeowners — none have been reported here yet.
Confirm the current fee directly with Montgomery County Department of Permitting Services ((240) 777-0311). If you have paid for a permit here, you can add it here to help others.
Montgomery County Building Department
Office: Montgomery County Department of Permitting Services
Address: 2425 Reedie Dr 7th floor, Wheaton, MD 20902, USA
Phone: (240) 777-0311
Source: official Montgomery County government records. Hours and procedures can change — call ahead to confirm.
How to Apply in Montgomery County
In Montgomery County, you can begin your application online through the county's permit portal, or submit blueprints and a property survey in person. Including your contractor's Maryland Home Improvement Commission (MHIC) license number helps avoid rejections.
ADU Construction Requirements in Montgomery County
Typical Submittal Package
When applying for a ADU Construction permit, you or your contractor will generally need to submit the following documentation for the city's review:
- Comprehensive architectural and structural plans
- Foundation engineering reports
- Sewer, water, and utility connection plans
- Site plan showing property lines and setbacks
Standard Ordinances & Processing Time
Key code points for a ADU Construction in Montgomery County: ADUs typically have maximum square footage limits (often 800-1200 sq ft), height restrictions, and usually require dedicated off-street parking depending on local zoning.
Typical processing time for a jurisdiction of this size: 4 to 8 weeks (High volume jurisdiction).
Frequently Asked Questions
What are the specific penalties for unpermitted ADU Construction work in urban Montgomery County?
Building without authorization is considered a code violation. The local government can issue a Stop Work Order, forcing you to halt construction immediately. You may be subject to retroactive permit fees (often double the original cost), daily fines, or even a mandate to tear down the unpermitted work at your own expense.
Can a homeowner pull their own ADU Construction permit in Maryland?
Yes. Maryland generally allows property owners to act as their own general contractor under an Owner-Builder exemption. If you take this route, you assume full legal and financial liability and must ensure all work complies with the Maryland Building Performance Standards.
How much does a ADU Construction permit cost in Montgomery County?
Permit fees vary by jurisdiction and by your project's valuation, so Montgomery County does not publish a single fixed figure. Confirm the exact fee with the local building department before applying.
How long does it take to get a ADU Construction permit in Montgomery County?
Based on the size of Montgomery County, the typical processing time is 4 to 8 weeks (High volume jurisdiction). Times vary with the season and the building department application volume.
Where do I apply for a ADU Construction permit in Montgomery County?
You can apply through the Montgomery County Department of Permitting Services or online via the county permit portal. For questions, call (240) 777-0311.
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Planning an ADU? Tools homeowners use in the design and layout phase:
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Backyard ADU Design Guide (Book)
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Laser Level
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Franklin ProSensor Stud Finder
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25ft Tape Measure
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Other Permit Types in Montgomery County
Planning another home improvement project? Check the requirements and fees for:
Nearby Jurisdictions in Maryland
Building near the county line? Check requirements for neighboring areas: