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Anne Arundel County, MD Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Anne Arundel County, MD, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Units allowed per lot: One accessory dwelling unit
Detached-structure size cap: Lesser of 800 sq ft or 50%
Address requirement: Same address, designated 'Unit B'
Grandfather date: In use before May 27, 2023
Governing section: County Code § 18-10-124

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Maryland under recent ADU streamlining laws. The Anne Arundel County, MD rules below cover local size, height, and setback requirements.

Summary

Anne Arundel County allows one accessory dwelling unit per lot in an attached suite, garage, or detached structure, capped at 800 square feet or half the main home's floor area.

City-specific rules exist: Annapolis has its own adu rules rules that differ from Anne Arundel County's county-level regulations. If you live in Annapolis, check the city-specific page instead.

An accessory dwelling unit shall comply with all of the following requirements. (1) No more than one accessory dwelling unit per lot is allowed. ... (4) An accessory dwelling unit located in a detached structure may not exceed the lesser of 800 square feet or 50% of the floor area of the principal single-family detached dwelling. ... (5) An accessory dwelling unit shall have a separate entrance. (6) ... shall use the same street address as the principal single-family detached dwelling and shall be designated as "Unit B".

Source: Anne Arundel County Code, Art. 18 (Zoning), Title 10 — ADUsView official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-93: County Code is current through May, 2026).

Full Breakdown

County Code § 18-10-124 permits one accessory dwelling unit per lot, built into the principal single-family home, connected by a breezeway, or placed in an attached or detached garage or other detached structure. A detached-structure ADU is capped at the lesser of 800 square feet or 50% of the principal dwelling's floor area, must have its own separate entrance, and is addressed as "Unit B" at the same street number as the main house. It cannot be a mobile or manufactured home. Either unit may be used for short-term rentals only if the owner occupies the property. ADUs in place before May 27, 2023 are grandfathered from the size, entrance, address, and short-term-rental rules unless altered or expanded afterward.

Violations & Fines

Zoning enforcement can order a noncompliant accessory dwelling unit brought into compliance or removed; adding a second ADU, exceeding the size cap, or converting without required permits is a violation.

Frequently Asked Questions

Can a Glen Burnie homeowner build a garage apartment?

Yes. Glen Burnie is unincorporated, so County Code § 18-10-124 governs directly and allows one ADU in an attached or detached garage.

How big can a detached ADU be?

No more than the lesser of 800 square feet or 50% of the principal home's floor area, per § 18-10-124(4).

Can the ADU be rented separately from the main house?

Short-term rental is allowed only if the owner occupies either the principal dwelling or the ADU, per § 18-10-124(7).

Sources & Official References

[1]Anne Arundel County Code § 18-10-124

Other rules in Anne Arundel County

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All Anne Arundel County rules

How Anne Arundel County compares: Easiest Cities to Build an ADU·Compare Anne Arundel County to another location·View the Maryland accessory structures overview

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ADU Rules in Cities Across Anne Arundel County

Annapolis, MD