Annapolis ADU Rules 2026: 850-Sq-Ft Limit, Historic Districts & HB 1466 Transition

Annapolis has its own accessory dwelling unit rules, separate from Anne Arundel County. The City has allowed ADUs under its own zoning framework since 2021, but several of those published rules now have to be read against Maryland’s HB 1466 framework and the October 1, 2026 local-law deadline. The result is a genuine transition period: Annapolis still publishes an 850-square-foot rule for ADUs outside the existing principal-building footprint, still requires owner occupancy, and has not yet been verified by this site as having enacted a final HB 1466 alignment ordinance.

1. Quick answer: can you build an ADU in Annapolis?

The crucial caveat is that these are Annapolis’s currently published local rules. They should not automatically be assumed to be the City’s final post-HB-1466 framework.

2. Annapolis City vs. Anne Arundel County: do not use the wrong rulebook

Annapolis is an incorporated municipality with its own planning and zoning authority. That means a house just inside the City boundary may have a materially different ADU path from a similar house in unincorporated Anne Arundel County.

Use our Anne Arundel County ADU Rules transition guide if the parcel is outside Annapolis City limits.

3. What Annapolis’s current §21.64.010 actually requires

The City’s current ADU framework was established through Ordinance O-9-21. Current City materials and the operative §21.64.010 provisions establish a set of baseline standards:

• One ADU maximum per lot.
• Location: within the principal structure or within an accessory structure.
• Separate ingress and egress: the ADU must have its own entrance/exit.
• Impervious surface: new impervious area must be treated/managed or equivalent impervious coverage removed elsewhere, as administered by the City.
• Size: an ADU not established within the existing footprint of the principal structure is capped at 850 sq ft of livable space.
• Rental license: required when the ADU is rented.
• Common ownership and owner occupancy: the ADU and principal structure must remain in common ownership and the owner currently must live in one of the two units.

4. Annapolis’s 850-sq-ft rule vs. Maryland’s 75% definition

This is the key 2026 regulatory question.

Maryland Land Use §4-501 defines a qualifying ADU as no greater than 75% of the size of the primary single-family detached dwelling. The statute does not itself state how that size must be measured. Maryland Department of Planning recommends finished living area above grade and interprets HB 1466 to mean local jurisdictions may not cap a qualifying ADU below the state’s 75% definition.

Annapolis, however, still publishes its pre-HB-1466 fixed 850-square-foot limit for an ADU outside the existing principal-building footprint. For a qualifying primary detached dwelling whose accepted reference size is greater than about 1,133 square feet, 75% would exceed 850 square feet.

Use our Maryland 75% ADU Size Guide & Calculator for the statewide measurement issue.

5. Owner occupancy: O-15-25 tried to remove it, but the bill was withdrawn

Annapolis’s current public FAQ still says the owner must live onsite in either the main dwelling or the ADU. That is consistent with the current §21.64.010 framework.

In 2025, Ordinance O-15-25 proposed removing that owner-residency requirement. It also proposed defining ownership and adjusting how short-term-rental licensing would work on an ADU property.

The legislative history matters: the Planning Commission did not recommend the ordinance in its original form and urged the Council to consider clarifying and streamlining ADU construction more broadly. After committee amendments and a public hearing, the City Council withdrew O-15-25 without objection on October 13, 2025.

6. Some Annapolis ADUs are by right; others need a special exception

The City’s current FAQ says ADUs are permitted in most residential zoning districts, including R1A, R1B, R1, R2, R3, R3-R, R4 and R4-R. It says ADUs may be permitted with a special exception in R2-NC, R3-NC, R3-NC2, C1 and C1A.

That distinction is not theoretical. Recent City Board of Appeals material includes an R2-NC application for an ADU above a proposed two-car detached garage, specifically because ADUs in that district require special-exception approval.

A special exception adds another entitlement step before the building permit. The City’s ADU guide tells applicants who need a special exception to obtain that approval first, revise plans for Board of Appeals conditions if necessary, and then submit the building-permit package.

7. Parking: Annapolis currently says no additional ADU parking is required

Annapolis’s current ADU FAQ answers the parking question simply: no additional parking is required for an ADU.

That makes Annapolis different from jurisdictions trying to preserve an additional ADU parking mandate. Maryland Land Use §4-504(e) requires a parking study and waiver process when a local law imposes additional off-street parking specifically for ADUs. Because the City’s current published ADU rule does not impose an additional space, we do not identify an HB 1466 ADU parking-study trigger here.

This does not mean parking, driveways, alley access or site circulation can never matter to a particular project. It means the City’s current ADU FAQ does not add a separate ADU parking-space requirement. See our Maryland ADU Parking Rules & Parking Study Tracker.

8. Garage conversions are explicitly recognized in Annapolis

The City’s FAQ says an ADU can be created through a garage conversion, attached or detached, or constructed as a new detached structure. That makes Annapolis one of the clearer Maryland municipal examples for homeowners considering an existing garage.

The City’s design guidance also says to consult a licensed structural engineer when an ADU is proposed above an existing structure such as a garage. If a garage conversion or expansion creates additional impervious surface, the stormwater rules discussed below can also apply.

See Can I Convert My Garage Into an ADU in Maryland? for the statewide conversion issues.

9. Stormwater, impervious surface and separate water/sewer can be the real cost drivers

Annapolis’s ADU guide tells applicants to plan for separate water and sewer connections and stormwater-management requirements. The City’s stormwater guidance is explicit that ADUs increasing impervious area on a site require stormwater management.

The current §21.64.010 framework also says new impervious surface on an ADU lot must be treated or managed, or equivalent impervious coverage removed elsewhere on the property. This can make a detached backyard structure more complicated than an interior conversion even when both satisfy the zoning-use rule.

• Site plan: the City guide calls for a site plan showing property lines, proposed ADU, existing structures, trees, topography, utilities and stormwater features where needed.
• Critical Area: projects in the Critical Area are subject to additional standards.
• Grading: separate grading thresholds can apply depending on disturbance area and earthwork.
• Utilities: the City’s published ADU guide instructs applicants to plan for separate water and sewer connection.

These requirements are one reason an Annapolis ADU that “fits” under the zoning envelope may still be expensive or technically difficult.

10. Historic District: zoning approval is not the only approval

If the property is in the Annapolis Historic District, exterior work has an additional review layer. The City’s building-permit guidance says all exterior projects in the Historic District require a Certificate of Approval, even when the work might otherwise be exempt from a building permit.

The Historic Preservation Commission reviews applications to construct, alter, rehabilitate, restore, reconstruct, move or demolish protected sites and structures. For an ADU, this can affect a detached structure, garage alteration, new exterior entrance, roof changes, windows, materials and other visible exterior work.

11. Annapolis setbacks: there is no safe single Citywide ADU number

The City’s ADU guidance tells homeowners to check the bulk standards of the applicable zoning district for setbacks from streets and adjacent properties. It does not publish one universal Annapolis ADU setback.

Maryland’s HB 1466 adds an important protection for qualifying ADUs: a local side or rear ADU setback may not be more restrictive than the jurisdiction’s existing side/rear setback for accessory structures. That still does not turn Annapolis into a one-number setback jurisdiction because the underlying standards can vary by zoning district and site condition.

Use our Maryland ADU Setback Rules lookup guide for the statewide framework, then verify the Annapolis zoning district and current bulk table.

12. Annapolis ADU permit workflow

13. Questions to ask Annapolis Planning & Zoning before paying for plans

1. Which ADU use category applies in this zoning district? Is it permitted or does it require a special exception?
2. How is the City currently reconciling §21.64.010(E)’s 850-sq-ft rule with Maryland’s 75% ADU definition?
3. For this property, what measurement of the primary dwelling will the City accept for the state 75% analysis?
4. Does the current owner-occupancy requirement remain applicable to this project?
5. What side, rear, street-side and accessory-structure setbacks apply in this zoning district?
6. Will this design create new impervious area requiring stormwater treatment?
7. What exactly does the City require for separate water and sewer connection on this parcel?
8. Is Historic Preservation Commission approval required before permit submission?
9. Is the property within the Critical Area or another overlay that changes the site plan?
10. What rental-license requirements will apply if the ADU is leased?

14. Bottom line

Annapolis is not Anne Arundel County for ADU zoning. The City already has a functioning ADU program, but its published 2021 framework now sits in a 2026 transition: the 850-sq-ft outside-footprint rule raises a state-alignment question, owner occupancy remains after O-15-25 was withdrawn, and City-specific special-exception, stormwater, utility and Historic District requirements can control feasibility.

The safest planning sequence is therefore: confirm City jurisdiction → zoning district → approval type → historic/environmental overlays → size interpretation → utilities/stormwater → building permit.

Primary sources used for this Annapolis guide

• City of Annapolis — Accessory Dwelling Unit Guide
• City of Annapolis — ADU FAQs
• Annapolis City Code — Chapter 21.64 / §21.64.010 Accessory Dwellings
• City of Annapolis — O-15-25 legislative record
• City Council — October 13, 2025 record withdrawing O-15-25
• City of Annapolis — Stormwater Guidance and Forms
• City of Annapolis — Building Permit Information
• City of Annapolis — Historic Preservation Division
• City of Annapolis — Historic District Streets and Zones
• Maryland Department of Planning — HB 1466 FAQ
• Maryland Land Use §4-501 — ADU definition
• Maryland Land Use §4-504 — local ADU requirements

Maryland ADU Guide is maintained by Gijo John as an independent research publication. We prioritize enacted code, official legislative records, current municipal guidance and state sources. Proposed legislation is not treated as law. Source-backed corrections can be sent to gijo.j@marylandaduguide.com.