HB1538 (Maryland Generational Housing Act of 2026) forces local jurisdictions to adopt laws allowing accessory dwelling units (ADUs) on single‑family detached lots and creates statewide limits on how localities and utilities can treat those units. The bill defines internal and external ADUs, requires at least one of each type per qualifying lot notwithstanding local density limits, and constrains local parking, setback, and fee regimes.
Beyond zoning, the bill restricts utility connection and capacity charges for ADUs occupied by eligible family members, allows meter and lateral sharing, bars development excise and impact fees for ADUs under 1,000 sq ft, and exempts family‑occupied ADUs from property tax for taxable years after June 30, 2026. For municipal and county administrators, housing policy teams, utilities, and tax offices, the act replaces broad local discretion with specific statewide ceilings and operational duties that will trigger administrative and fiscal adjustments.
At a Glance
What It Does
Mandates that each Maryland legislative body adopt an ADU law by October 1, 2026, and requires those laws to authorize at least one internal and one external ADU per single‑family lot regardless of local density caps. It also narrows local parking authority, limits utility connection and capacity fees for family‑occupied ADUs, permits meter sharing, prohibits certain local development fees for ADUs under 1,000 sq ft, and creates a property tax exemption for ADUs occupied by qualified family members.
Who It Affects
Single‑family homeowners who want to add ADUs (particularly for relatives), local planning and code departments required to revise ordinances and complete parking studies, water/sewer utilities that must change fee and metering practices, and county/municipal finance offices that will lose certain fee revenue streams.
Why It Matters
The bill shifts many decisions from local discretion to state‑mandated floors and ceilings—expanding legal entitlement to build ADUs while constraining how localities and utilities can charge and regulate them. That combination accelerates supply potential but raises questions about infrastructure capacity, enforcement, and local fiscal tradeoffs.
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What This Bill Actually Does
HB1538 rewrites Maryland’s accessory dwelling unit framework in three linked ways: definitions and entitlements, limits on local requirements and fees, and a narrowly targeted tax exemption. The bill enlarges the statutory definition of ADUs to distinguish internal units (inside the primary dwelling footprint) from external units (detached backyard cottages, carriage houses, modular units) and caps an ADU’s size at 75% of the primary residence.
It makes the state’s policy explicit: localities must adopt ADU laws that conform to the statute and, crucially, must authorize at least one internal and one external ADU per single‑family detached lot regardless of any locally adopted density ceilings.
On local controls, the statute constrains what a jurisdiction may impose. Local laws must meet building safety and public‑facilities standards but cannot count an ADU toward density caps.
Setback authority for ADUs cannot exceed existing accessory‑structure side and rear setbacks. The bill also tightens parking rules: jurisdictions must conduct a parking study before increasing parking requirements and may not mandate additional off‑street parking for ADUs that are conversions of interior space or existing accessory structures; they must also offer a waiver process where they do set requirements.The bill inserts concrete limits on utilities and local finances.
Utilities may not charge property owners constructing ADUs to be occupied by a ‘qualified family member’ connection fees above the administrative cost of a permit, nor capacity/tap fees if the combined bedroom count will not exceed an existing septic system’s capacity; utilities must allow meter and service‑lateral sharing at the owner’s request. Counties and municipalities are barred from imposing development excise taxes or development impact fees on ADUs smaller than 1,000 square feet.
Finally, the bill adds a property‑tax exemption: an ADU occupied by a qualified family member is not subject to property tax, effective for taxable years starting after June 30, 2026.
The Five Things You Need to Know
Each county and municipality must adopt a local law authorizing ADUs by October 1, 2026, and those laws must allow at least one internal and one external ADU per single‑family detached lot notwithstanding local density limits.
The bill defines ADUs as secondary units up to 75% of the primary dwelling’s size and explicitly includes internal conversions (basements, attics, attached garages) and detached external units (backyard cottages, carriage houses, modular units).
Local governments may not require additional off‑street parking for ADUs that are conversions of interior space of the primary dwelling or of an existing accessory structure; any new parking rules require a prior parking study and must include a waiver process.
For ADUs that will be occupied by a qualified family member, utility providers cannot charge water/sewer connection fees above administrative permit costs or capacity/tap fees when the combined bedroom count stays within existing septic capacity, and utilities must permit meter and service‑lateral sharing upon owner request.
ADUs occupied by qualified family members are exempt from property tax for taxable years beginning after June 30, 2026, and counties/municipalities may not impose development excise or development impact fees on ADUs under 1,000 sq ft.
Section-by-Section Breakdown
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New ADU definitions, size cap, and family relationship rules
This section adds precise statutory language for accessory dwelling units, splitting the concept into internal and external ADUs, and sets a size limit (not greater than 75% of the primary dwelling). It also creates a statutory definition of “qualified family member” that includes parents, grandparents, children, grandchildren, siblings and relationships by adoption or marriage. For compliance officers and ordinance drafters, the definitions narrow ambiguity that previously existed at the local level and will be the baseline for code revisions.
State policy and mandatory local adoption of ADU laws
The bill requires each local legislative body to adopt an ADU law by October 1, 2026, directing jurisdictions to allow ADU development consistent with building codes and public‑facility standards. Importantly, the statute elevates state policy promoting ADUs and requires local policies to ‘further the intent’—a phrase that gives the state leverage when local ordinances are silent or restrictive. Practically, municipalities must reconcile existing zoning codes with required ADU allowances and safety standards.
Density exemption, setback limits, and parking study/waiver rules
Section 4‑504(c) excludes ADUs from density calculations and expressly requires that, regardless of any local density limit, at least one internal and one external ADU be permitted per eligible lot. Subsection (d) constrains setback authority to existing accessory‑structure side and rear setbacks. Subsection (e) conditions any additional off‑street parking requirements on a prior parking study and mandates a waiver process; it also forbids additional parking mandates for ADUs created by converting interior space or existing accessory structures. These mechanics shift the local debate from whether ADUs are allowed to how they are implemented.
Limits on utility connection/capacity fees and mandated meter/lateral sharing
This provision prevents utility providers from charging owners constructing ADUs to be occupied by qualified family members connection fees above the administrative cost of a permit, and it bars capacity/tap charges where the combined bedroom count remains within an existing septic system’s capacity. It also requires utilities to permit, at the owner’s request, sharing of meters and service laterals between the ADU and the primary dwelling. Operationally, utilities will need to update tariff schedules and develop procedures for technical reviews and shared billing arrangements.
Prohibition on development excise and impact fees for small ADUs
This new local government provision forbids counties and municipalities from imposing development excise taxes or development impact fees on the construction of ADUs smaller than 1,000 square feet. That creates a clear fiscal exemption for small ADUs and limits a common revenue tool used to offset capital costs associated with new housing; local finance offices will need to quantify lost fee revenue and consider alternatives for recouping infrastructure costs.
Property tax exemption for family‑occupied ADUs and effective date
The Tax‑Property addition exempts ADUs from property tax when occupied by a qualified family member, with applicability for taxable years beginning after June 30, 2026. Tax assessors must adopt procedures to identify qualifying occupancy, determine valuation practice for combined parcels, and monitor ongoing eligibility—creating administrative work for local tax offices and new ways homeowners might structure occupancy to obtain the exemption.
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Explore Housing in Codify Search →Who Benefits and Who Bears the Cost
Every bill creates winners and losers. Here's who stands to gain and who bears the cost.
Who Benefits
- Homeowners seeking to house family members: The law guarantees the right to create at least one internal and one external ADU and limits local parking and fee barriers, making multigenerational arrangements legally and financially easier.
- Qualified family members (elderly relatives, adult children): Those living with homeowners gain more living options because meter sharing, limited utility fees, and a property‑tax exemption reduce carrying costs for family‑occupied units.
- Modular and small‑scale ADU builders: Clear statewide allowances and an explicit exemption from development fees for units under 1,000 sq ft create a more predictable market for backyard cottages, carriage house conversions, and modular systems.
- Housing advocates and planners focused on gentle density: The statute removes major local barriers to incremental housing supply by preventing density counts from blocking ADU creation and limiting local fees that can make small units uneconomic.
Who Bears the Cost
- County and municipal finance departments: The ban on development excise and impact fees for sub‑1,000 sq ft ADUs and the property tax exemption reduce common local revenue streams for capital and operating budgets.
- Water and sewer providers: Utilities may lose connection and tap revenue for family‑occupied ADUs and will need to create technical, billing, and inspection processes to allow meter/lateral sharing.
- Local planning and code enforcement offices: Jurisdictions must rewrite zoning and building regulations, complete parking studies where they change parking rules, administer waiver processes, and create procedures to verify family occupancy for tax exemptions.
- Neighbors and local infrastructure funders: Residents adjacent to new ADUs may experience increased parking and service demands; absent new local fees, infrastructure upgrades may require alternative funding sources or higher general revenues.
Key Issues
The Core Tension
The bill balances two legitimate objectives—expanding affordable, multigenerational housing by removing local barriers, and preserving local control to manage neighborhood character, infrastructure capacity, and fiscal health—by privileging state entitlements and limiting local fees, a trade‑off that accelerates housing rights while shifting costs and operational complexity onto utilities and municipal administrations.
The bill creates clear entitlements but leaves several practical and enforcement questions unresolved. First, the property‑tax exemption is occupancy‑based: local tax assessors must determine when an ADU is genuinely occupied by a qualified family member versus serving as a rental.
The statute does not specify documentation, duration thresholds, or audit mechanisms, which will require implementing rules to prevent fraud and inconsistent application across counties.
Second, the utility provisions trade fee revenue for ease of household expansion, but they do not detail technical standards for meter sharing or liability allocation for service laterals. Small municipal utilities and private providers will need to adopt engineering protocols, revise tariffs, and decide who pays for physical reconfiguration—costs the statute largely leaves to administrative rulemaking or bilateral negotiation.
Third, by forbidding development impact/excise fees for ADUs under 1,000 sq ft, the act shifts capital cost recovery away from the marginal development that creates demand for infrastructure; localities must either absorb those costs, increase other fees, or deprioritize upgrades.
Finally, the mandated density carve‑outs and limits on parking requirements may intensify neighborhood pushback, creating political pressures around enforcement and compliance. The requirement for jurisdictions to conduct a parking study before imposing parking rules is useful, but the statute does not impose minimum methodological standards for those studies; inconsistent studies could produce uneven local outcomes.
Collectively, these gaps create implementation burdens for utilities, tax offices, and local governments that are not matched with explicit funding or procedural detail in the bill text.
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