Plan your Maryland ADU from local jurisdiction and feasibility through size, site constraints, budget and contractor bids. Start with the Maryland ADU Jurisdiction Finder, then build your property verification checklist.
Use these Maryland ADU planning tools before you commit to design, financing, prefab deposits or construction. Each tool answers a different feasibility question and shows where local verification is still required.
Start here
Find the government that controls your property first
Enter the property street address in the Maryland ADU Jurisdiction Finder first. It checks Maryland government county and municipal boundary data, separates zoning authority from building-permit authority, and routes you to the correct local guide before you size or price the project.
Your step-by-step ADU planning path
New to ADUs? Start below. Already researching a property? Jump to feasibility, size, placement, utilities, budget, financing or your project team. You can return here whenever you need the next step.
Before step 1: read the rules for your actual jurisdiction
After finding the reviewing office, open your local guide in the County Rules Tracker or local guide directory. A mailing address alone does not establish who controls zoning. Read the state law overview and October 1 deadline guide if you need the statewide context.
Take away: the responsible office, the current local source and the questions you still need that office to answer.
1. Does the property have a workable ADU path?
Considering an interior conversion? Use the basement ADU guide to prepare questions about ceiling height, bedroom escape openings and the existing structure.
Take away: a prioritized list of property questions. Check HOA and private restrictions early. For an existing garage, follow the garage conversion branch before assuming the building is suitable.
After the jurisdiction is resolved, run the Maryland ADU Property Feasibility Checker. Its seven guided steps turn unknowns about dwelling type, size evidence, placement, utilities, private restrictions and intended use into a prioritized verification checklist. For detached or exterior projects, use the new Maryland ADU Site Plan Guide to map setbacks, easements, septic, utilities, parking and the preliminary buildable area before you pay for final plans.
2. How large could my ADU be?
Take away: the measurements and local size method you need to verify. After you know the likely maximum, compare 400, 600, 800 and 1,000 sq ft ADU layout concepts before paying for final design.
Use the Maryland ADU Size and Measurement Guide to check the measurement evidence your jurisdiction requires. Confirm the applicable measurement method before relying on a legal size calculation. Howard’s shared record also flags parking and dwelling-type conflicts; its FAQ separately describes an exterior-footprint method.
3. Where can I place the ADU?
Take away: a sketch showing the proposed location, boundaries, access and parking questions for local review.
For the definitions, a worked example and stormwater review questions, read the Maryland ADU lot coverage guide.
Use the Maryland ADU Setback Rules & Lookup Guide to understand the local accessory-structure setback standard, then check the Maryland ADU Parking Rules Tracker for parking studies, waivers and local exceptions.
4. Will septic or private well conditions complicate the project?
Take away: the records and utility questions to resolve before design. If the property uses public water and sewer, ask the providers about capacity and connection requirements instead.
Use the Septic & Well Readiness Checker to identify whether records review, Health Department review, reserve-area verification or more complex site work may be needed.
5. What should I budget?
Take away: an itemized planning budget with exclusions and unknowns visible. Include ongoing ownership costs using the property tax guide.
Start with the Maryland ADU Cost Escalation Guide to identify site work, utilities, delivery, permitting and other scope items that can sit outside a headline quote. Then use the Maryland ADU Cost Calculator & Bid Comparison Tool to build an editable planning budget, download a CSV and compare the scope completeness of up to three contractor bids.
Optional branch: planning for an aging parent
Use this comparison if family care is part of your project. Otherwise, continue to financing below.
Use the Maryland ADU vs. Assisted Living Cost Planner to compare cash outlay using your own ADU budget, in-home care needs and a verified Maryland assisted-living benchmark. It keeps housing and care costs separate and now includes an aging-parent design brief covering entry, circulation, bathroom layout, one-level living, lighting, privacy and emergency access—without presenting those design ideas as universal Maryland code requirements.
6. How could I finance the project?
Take away: a funding shortlist and questions to discuss with lenders using your project budget.
Use the Maryland ADU Financing Guide to compare HELOCs, home-equity loans, cash-out refinancing, Fannie Mae HomeStyle Renovation and FHA Standard 203(k), with Maryland-specific program cautions and lender questions.
7. Who will help me design and price the project?
Ready to build a shortlist? Browse the Maryland ADU professional directory by county, project type and service, then review each profile’s evidence and confirm current credentials. You can also submit a project request. Requests are accepted while the referral network is being developed; a professional match or introduction is not guaranteed.
Prepare a project brief with your local-rule questions, site constraints and budget. Use the architect hiring guide to define the design scope, then the builders and prefab guide to request comparable bids. Bring quotes back to the bid comparison tool to check missing scope before choosing a proposal.
Take away: a clear scope of work and a list of permit questions to confirm with the reviewing office. Design, pricing and permit review may require you to revisit earlier steps.
8. How do I get from plans to a completed ADU?
Use the Maryland ADU Permits to Completion Guide to prepare your application and get through review. Once permits are issued, switch to the Maryland ADU Construction Timeline for the build sequence from site work and foundation through rough inspections, finishes and final approval.
Take away: a record of the next permit or inspection action, who handles it and which approvals remain before occupancy.
Rule-friction checklist: what can make a permitted ADU harder to execute?
Want the statewide research snapshot first? Open the Maryland ADU County Framework Status Dataset to compare all 24 county-level jurisdictions and download the current filtered table as CSV.
A local ordinance can technically allow ADUs while still adding cost, delay or uncertainty. Before spending on plans, use the County Rules Tracker and local code to answer these questions:
- Approval path: Is the ADU administrative/by-right when standards are met, or does it require a special exception, hearing or other discretionary approval?
- Parking: Is additional off-street parking required, and are there waivers or location-based exceptions?
- Owner occupancy: Must the property owner live in the main dwelling or ADU?
- Utilities: Are separate water/sewer taps, meters or connection fees required, or can services be shared?
- Lot and dimensional limits: Do minimum lot size, setbacks, lot coverage, height or another local cap reduce the practical buildable area?
- Building code: Could sprinklers, fire separation or egress change the design? Use the Maryland ADU building-code guide.
- Existing or unpermitted unit: Is the dwelling legally existing, nonconforming or unapproved? Use the existing ADU legalization guide before assuming it is grandfathered.
- Critical Area: Is the parcel in an IDA, LDA or RCA, or affected by the 100-ft Buffer? Use the Maryland Critical Area ADU guide.
- Historic review: Is the property in a local historic district or separately listed/eligible for historic registration? Use the Maryland historic-district ADU guide.
- Rental use: Are long-term rental, short-term rental, licensing or occupancy rules relevant to how you plan to use the ADU?
Why we track these: a Maryland Department of Planning-hosted 2021 Smart Growth webinar by land-use attorney/planner Donald Elliott identified parking, discretionary approval and new utility/tap requirements among the recurring forms of ADU regulatory friction seen around the country. The webinar is expert commentary, not Maryland law; our county pages use current statutes, ordinances and official local records for actual requirements. View the webinar background.
These are planning tools, not permit determinations, engineering calculations, lender approvals or contractor recommendations. Verify property-specific requirements with the relevant local authority before acting.
What to do next
Start by finding the office that reviews your property. A mailing city or a county guide does not establish your parcel’s authority.
- Find Who Reviews My Property.
- Obtain your parcel identifier, survey, floor plans and utility records.
- Ask the reviewing office which current rules, supporting documents and approvals apply.
- Continue to your planning workspace.
Enable JavaScript to prepare a downloadable next-step brief. Planning guidance is not permit approval.