Maryland ADU Site Plan Guide 2026: What to Show Before You Apply

Last researched: September 19, 2026. A site plan is one of the most useful documents you can prepare before spending heavily on an accessory dwelling unit (ADU) in Maryland. It helps a planner, designer, contractor or permitting office see how the proposed ADU fits on the property—and whether setbacks, easements, utilities, septic areas, parking, lot coverage or other constraints may interfere with the project.

Homeowner takeaway: Before buying a prefab ADU or paying for final architectural plans, identify your jurisdiction, obtain the best property survey available, sketch the ADU location, and mark the constraints that can shrink the buildable area. Use our Maryland ADU Jurisdiction Finder first if you are unsure which county or municipality controls your zoning.

Maryland ADU site plan: annotated example

What should an ADU site plan show?

Exact requirements vary by jurisdiction, but Maryland permit materials provide a useful baseline. Frederick County’s residential accessory permit instructions call for a plot plan showing property lines and dimensions, lot area, building restriction lines, utility easements, a north arrow, drawing scale, owner/address information, the existing dwelling and other existing structures. Anne Arundel County similarly requires site plans to show proposed work, easements, property lines, rights-of-way, and—where applicable—grinder pumps, private wells and septic systems.

For an ADU planning-stage site plan, try to show at least:

• property boundaries and dimensions;
• street frontage and north arrow;
• existing primary dwelling;
• existing garages, sheds, decks, pools and other structures;
• the proposed ADU footprint and approximate dimensions;
• distance from the ADU to side and rear property lines;
• distance between the ADU and the primary house;
• recorded easements and building restriction lines;
• driveways and proposed vehicle access;
• existing/proposed parking areas;
• water and sewer connections or private well/septic locations;
• septic reserve area, when applicable;
• utility corridors or likely connection routes;
• streams, floodplain, Critical Area or other environmental constraints when relevant;
• lot area and, where relevant, impervious or lot-coverage calculations.

1. Start with the correct Maryland jurisdiction

A technically neat drawing can still be useless if you apply the wrong zoning rules. Maryland ADU standards are implemented through counties and municipalities with planning and zoning authority. Maryland law requires covered local governments to authorize ADUs consistent with HB 1466, but local application processes, zoning maps, overlays and permit requirements still matter.

Use our Jurisdiction Finder before measuring setbacks. A mailing address may not tell you whether county or municipal zoning controls the parcel.

2. Get the best existing survey you can find

Look through your settlement documents, title package, prior permit records or property files for a boundary/location survey. Frederick County specifically recommends using a legal survey when possible for residential accessory work.

A survey is valuable because fences, driveways and landscaping are not reliable substitutes for legal property lines. Building an ADU based on an assumed boundary can create expensive redesign or permitting problems.

3. Draw the existing conditions before drawing the ADU

Mark the house and every meaningful existing structure first. Include garages, sheds, decks, patios, pools and similar improvements. Existing structures matter because they can consume lot coverage, conflict with setbacks or reduce access to the proposed unit.

This is especially important when using our Maryland ADU lot coverage guide: zoning permission for an ADU does not automatically mean the lot has enough remaining buildable area.

4. Mark side and rear setbacks

Maryland’s current ADU framework says a local ADU law may not establish side or rear setbacks that exceed the jurisdiction’s existing accessory-structure setbacks. That does not create one universal statewide setback number, so the correct local rule still needs to be identified for the parcel.

Read our Maryland ADU setback guide, then confirm the current local ordinance before treating the resulting envelope as final.

5. Treat easements as potential no-build zones until verified

Utility, drainage, access and other recorded easements can run through the area that initially looks perfect for a detached ADU. Frederick County explicitly asks applicants to identify utility easements and building restriction lines on plot plans, while Anne Arundel requires easements to be shown on its site plans.

Do not assume an easement makes construction impossible in every case, but do not ignore it either. Find out who controls the easement and what approvals would be required.

6. Show well, septic and reserve areas early

For properties using private septic, the backyard is not simply “empty buildable land.” The existing septic system, replacement/reserve area, well separation requirements and proposed additional bedroom/occupancy load may affect feasibility.

Anne Arundel’s permit guidance expressly requires private well and septic systems to be identified on applicable site plans. Maryland’s ADU framework also preserves public-health and facility-capacity requirements. Use our Maryland ADU septic & well guide and ADU Property Feasibility Checker before committing to a backyard location.

7. Sketch the utility path—not just the building

A detached ADU needs more than enough physical space for four walls. Think through how water, sewer/septic, electricity and communications will reach it. Long trench runs, hardscape crossings, mature trees or conflicts with easements can make a seemingly easy location expensive.

Our Maryland ADU utilities guide explains why meter, connection and utility requirements should be investigated before final design.

8. Show parking and access even when extra ADU parking may not be required

HB 1466 prevents a jurisdiction from imposing additional ADU parking requirements without first completing the parking study required by the statute. But the property still needs to function safely, and existing driveways, garages, fire access and local rules can remain relevant.

Showing the current driveway and likely access to the ADU makes the site plan more useful even where no new parking stall is required. See our Maryland ADU parking guide.

9. Check environmental and historic overlays

Some Maryland properties have constraints that are easy to miss on a simple backyard sketch: Chesapeake Bay Critical Area requirements, floodplain, forest conservation, stormwater, steep slopes, historic districts or locally protected resources.

Prince George’s County’s homeowner permitting guidance, for example, identifies floodplain, Chesapeake Bay Critical Area and historic review as issues that can trigger additional review. This is another reason a site plan should be treated as a constraint-finding tool, not merely a permit drawing.

10. Know when a sketch is no longer enough

A rough homeowner drawing can be excellent for early feasibility discussions. It is not automatically sufficient for a permit. Some Maryland jurisdictions require plans at an engineered or recognized scale, and certain applications may need a surveyor, architect or engineer.

Anne Arundel County requires applicable site plans to be drawn to an engineered scale. Prince George’s County requires signed/sealed site plans for several residential permit types. Always check your specific permit category rather than assuming a planning sketch can be submitted unchanged.

ADU site-plan workflow for Maryland homeowners

1. Identify the zoning jurisdiction.
2. Obtain the survey/plat and property records.
3. Mark property lines and existing structures.
4. Identify zoning district and overlays.
5. Draw the preliminary ADU footprint.
6. Mark required side/rear setbacks.
7. Add easements and building restriction lines.
8. Add driveway, parking and access.
9. Add well, septic and reserve area if applicable.
10. Sketch utility routes.
11. Check lot/impervious coverage.
12. Ask the reviewing jurisdiction what is missing before paying for final plans.

Common ADU site-plan mistakes

What to send a planner for an early ADU feasibility question

For an initial discussion—not a formal application—a concise package can make the conversation much more productive:

• property address and parcel/account information;
• existing survey or plat;
• simple annotated site plan;
• approximate ADU dimensions and height;
• whether it is detached, attached, garage conversion or interior;
• desired number of bedrooms;
• known water/sewer or septic/well information;
• photos of the proposed location;
• a short list of specific questions about setbacks, lot coverage, utilities and approval path.

Once basic feasibility is established, compare practical layouts in our Maryland ADU Floor Plans guide, then use the Maryland ADU architect hiring guide and permit-to-completion guide for the next stage.

Maryland ADU site plan FAQs

Do I need a site plan for a Maryland ADU?

For detached or exterior ADU work, expect the reviewing jurisdiction to need site/plot information showing where the work sits on the lot. Exact submittal requirements vary. Interior-only conversions may have different requirements.

Can I draw an ADU site plan myself?

You can create a rough planning sketch yourself, and some jurisdictions allow certain homeowner-drawn plot plans when they are accurate, legible and to scale. A formal permit application may require a survey, engineered scale or signed/sealed plan depending on the jurisdiction and project.

What scale should an ADU site plan use?

There is no single Maryland-wide scale for every ADU permit. Follow the reviewing jurisdiction’s requirements. For example, Anne Arundel County states that site plans must be drawn to an engineered scale.

Should a site plan show septic and wells?

Yes when the property relies on them or they affect review. Anne Arundel County specifically asks applicable site plans to show private wells and septic systems, and septic capacity/reserve area can be a major ADU feasibility constraint.

Does an ADU site plan need parking?

Show existing/proposed parking and access when relevant even if the jurisdiction does not require a new ADU parking space. It helps reviewers understand circulation and site constraints.

Is the sample site plan on this page permit-ready?

No. It is an educational planning diagram showing the types of constraints homeowners should identify. Your jurisdiction determines the actual permit drawing requirements.

Primary sources checked

• Maryland Department of Planning — Accessory Dwelling Units
• Maryland Department of Planning — HB 1466 ADU FAQ
• Frederick County — Residential Addition, Alteration & Accessory Permit Information
• Anne Arundel County — Residential Accessory Structure Permit Requirements
• Prince George’s County — Residential Addition Permit Requirements

Maryland ADU Guide is an independent research publication, not a county or municipal permitting agency, surveyor, architect, engineer, contractor or law firm. This guide is for early planning. Confirm current parcel-specific zoning, environmental, utility, health-department and permit requirements before relying on a drawing for construction or permit submission.