Maryland ADU Feasibility Checker: 6-Step Property Screen

Use this screening tool to identify the Maryland, county, private-rule, size, utility and budget questions that should be verified before you pay for plans or construction. It is a planning aid—not a permit decision, zoning determination, legal opinion or lender approval.

Maryland ADU Property Feasibility Checker

6 short steps. Identify the issues to verify before you spend.

Runs in your browser. No property answers are submitted to us.

Step 1 of 6 · Location

Where is the property?

County implementation is moving at different speeds. We use the county only to route you to the right verified material.

Maryland county or Baltimore City

Could a municipality have its own planning or zoning authority for this property?

Yes / the property is inside a municipalityI may need to verify municipal rules in addition to county information.

No municipality identifiedI believe county rules are the local zoning layer.

Not sureI need to confirm which local government has planning and zoning authority.

HB 1466 applies to counties and municipalities that have planning and zoning authority, so county selection alone may not always identify the final local rule set.

Step 2 of 6 · State-law baseline

What is the primary home?

HB 1466’s statewide ADU definition is tied to a primary single-family detached dwelling. Other housing types may be governed differently by local law.

Is the existing primary home a detached single-family dwelling?

YesA stand-alone single-family house.

NoFor example, a townhouse, duplex or multifamily property.

Not sureI need to confirm the property’s legal dwelling type.

What type of ADU are you considering?

Interior conversionSpace wholly or mostly within the existing house.

Attached additionA new unit connected to the primary dwelling.

Detached ADUA separate backyard cottage or converted accessory structure.

Not sure yetI am still comparing configurations.

Step 3 of 6 · Size screen

Does the proposed size pass a basic 75% screen?

Maryland defines an ADU as up to 75% of the primary detached dwelling’s size, but the State does not prescribe one universal measurement method. Treat this as a screening calculation only.

Primary dwelling reference size (sq ft)Howard County uses exterior footprint for its 75% method. Elsewhere, confirm the local measurement method.

Proposed ADU size (sq ft)Leave blank if you have not selected a size yet.

Enter both numbers to see the screening calculation.

Step 4 of 6 · Utilities and site

How is the property served?

Utility and wastewater constraints can change the project before floor-plan design begins.

Water / wastewater situation

Public water and public sewerI am connected to both public systems.

Private well and/or septicAt least one system is private or on-site.

Not sureI need to confirm the property’s service type.

If septic/well is involved, has the relevant health authority confirmed capacity / reserve-area issues for the ADU?

YesI have project-specific confirmation or current records.

No / not yetThis still needs to be checked.

Step 5 of 6 · Private restrictions

Is an HOA or recorded covenant involved?

Maryland limits unreasonable private restrictions on qualifying ADUs, but private documents still need to be reviewed separately from zoning.

Is the property subject to an HOA or similar private restrictions?

NoI am not aware of an HOA or private covenant affecting the property.

YesThere is an HOA, declaration, covenant or architectural review process.

Not sureI have not checked the recorded documents yet.

Have you reviewed the actual HOA / covenant language that could affect an ADU?

YesI have the relevant rule language.

No / not yetI still need the declaration, bylaws or architectural rules.

Step 6 of 6 · Budget readiness

How complete is your project budget?

A low construction quote can be misleading if design, permits, utilities, site work, delivery or septic work are excluded.

Which best describes your current budget?

Scope-aware estimateI have separate allowances for design/engineering, permits, site/foundation, utilities and construction.

Partial estimate or contractor headline priceSome major scope categories are still unclear.

No working budget yetI am still in feasibility research.

County status

Choose your location first.

State baseline

HB 1466 took effect October 1, 2025. Covered local governments must adopt compliant local law by October 1, 2026.

What this checker does

Surfaces missing verification steps. It does not decide whether a permit will be issued.

Open county rules tracker →

Check ADU setback rules →

Source standard: State baseline from Maryland HB 1466 and the Maryland Department of Planning HB 1466 FAQ. County status is limited to jurisdictions we have individually verified. Last status review: September 7, 2026.