Planning an ADU in Howard County? CB 3-2026 is in effect, and the County currently allows qualifying attached and detached ADUs. The homeowner issues to check first are the 75% exterior-footprint size method, owner occupancy, the short-term-rental prohibition, and the parking requirement that still warrants confirmation with DPZ. Before applying, confirm that Howard County is the reviewing jurisdiction for the property with the Jurisdiction Finder, then use the Property Feasibility Checker to organize the parcel-level questions.
This guide separates published Howard County guidance from unresolved parking and dwelling-type discrepancies. The footprint explanation below is attributed to the county FAQ; the shared planning tools continue to require verification before producing a legal size result. For the statewide comparison, see our Maryland County ADU Rules Tracker.
Official verification update: September 29, 2026. Howard County Planning Supervisor Justin Tyler confirmed that the county’s ADU regulations are in Section 128.0.A.13 of the Zoning Regulations, that there are no current or proposed amendments to that ADU section, and that the county requires its ADU application before establishment of an ADU. The county application instructions and February 2 Council record were also reviewed. This page is informational and is not legal, zoning, architectural, engineering, or permitting advice.
Howard County ADU rules at a glance
| Question | Published guidance and verification needed |
|---|---|
| Effective date | CB 3-2026 became effective April 8, 2026. |
| ADU forms | Attached and detached ADUs are allowed in qualifying districts; existing space may also be renovated to create an attached ADU. |
| Maximum size | The county FAQ describes 75% of the principal dwelling’s exterior footprint. Confirm the accepted measurement and applicable limits for your application. |
| Owner occupancy | The property owner must reside in either the principal dwelling or the ADU. |
| Short-term rentals | Prohibited. The enacted amendment defines a short-term rental as lodging for fewer than 30 consecutive days for compensation. |
| Parking | Parking remains unresolved in this guide. The department summary describes three spaces; Council minutes say the amendment increasing one to three spaces was not moved. Request the current enforced requirement. |
| ADU permit | Zoning approval is required through the Department of Planning and Zoning before the ADU may operate. |
| Application fee | Howard County currently lists a $25 ADU application fee. |
What CB 3-2026 changed
Howard County describes CB 3-2026 as an expansion of ADU opportunities intended to align local zoning with HoCo By Design, the Housing Opportunities Master Plan, and Maryland’s statewide ADU law. The county says single-family homeowners may construct attached or detached ADUs or renovate existing space to accommodate an attached ADU in various residential zoning districts.
The county’s amendment summary distinguishes attached and detached ADU paths and excludes lots with two-family dwellings. Its FAQ definition still includes two-family dwellings. These statements conflict. Obtain a dwelling-type determination from DPZ rather than treating the FAQ definition as authorization.
Official source: Howard County Department of Planning and Zoning — Accessory Dwelling Units.
The footprint calculation: how large can your Howard County ADU be?
Howard County does not describe the limit as 75% of the home’s total finished living area. Its current FAQ says the maximum allowable ADU size is calculated from the exterior footprint of the principal dwelling, and the accessory unit may not exceed 75% of that footprint.
Open the Maryland ADU measurement workspace to record your measurement evidence and identify what still needs confirmation. A blocked calculation is not a finding that ADUs are prohibited.
That distinction can materially change a project. A two-story house may have substantially more interior floor area than ground-level footprint.
Lot coverage and stormwater can reduce what fits
The 75% calculation is a maximum-size rule, not a guarantee that the entire theoretical area can be built. Howard County’s adopted-ADU materials also apply lot-coverage standards to detached accessory structures, including ADUs.
For an ADU in a newly constructed structure, the county’s application page requires the plot plan to demonstrate adequate water conveyance so the project does not adversely affect neighboring properties or existing subdivision stormwater-management facilities.
Owner occupancy is required
Howard County requires the property owner to reside in either the principal dwelling or the ADU. The county’s application guidance states that an owner who wants to rent the other dwelling must first obtain zoning approval for the ADU.
If either the principal dwelling or the ADU will be rented, a rental license may also be required through the Department of Inspections, Licenses and Permits. Howard County’s current application guidance says the owner must obtain ADU zoning approval before applying for the rental license.
Short-term rentals are prohibited
CB 3-2026 was amended to prohibit ADUs from being used as short-term rentals. The enacted amendment defines a short-term rental as a dwelling, or part of one, used for lodging for fewer than 30 consecutive days in exchange for compensation, and specifically references platforms such as Airbnb and VRBO as examples.
So an ADU project intended primarily for nightly or weekly visitor accommodation should not be treated as a compliant Howard County ADU rental strategy.
How many parking spaces does a Howard County ADU need?
Parking summary rechecked October 18, 2026: DPZ’s ADU webpage still describes a three-space requirement. The records cited below explain why we have not treated that summary as a resolved parking rule. Ask DPZ to identify the controlling provision for your property before drawing the parking layout.
Parking evidence checked October 10, 2026: The signed, enacted CB3-2026 (printed pages 95–96) retains one off-street parking space per ADU, additional to the principal residence’s required parking (§133.0.D.1.a). Amendment 10 proposed three spaces but was not moved (February 2 Council minutes, page 13). DPZ’s current ADU webpage nevertheless lists three spaces. We have not independently verified the current codified text or resolved this discrepancy; confirm the applicable requirement with DPZ before finalizing your parking layout.
The County Council’s February 2, 2026 minutes describe Amendment 10 as increasing parking from one space to three with an exception, and record that Amendment 10 was not moved. The minutes do not explain why the department webpage lists the increase among adopted amendments.
Primary records: CB 3-2026 legislation record, final amended CB 3-2026 text, and February 2, 2026 Council session record.
How to apply for a Howard County ADU
Howard County requires an ADU application through the Department of Planning and Zoning. The application must include a plot plan showing compliance with the applicable maximum size and setback requirements.
For a newly constructed ADU structure, the plot plan must also address water conveyance and potential effects on neighboring property or subdivision stormwater facilities. The county application page lists a $25 ADU application fee, rechecked October 18, 2026. This is the ADU application charge, not a total project-permit budget. For construction budgeting, use the Maryland ADU cost calculator.
Howard County ADU application and current instructions.
Before paying for ADU plans: a Howard County checklist
The expensive mistake to avoid: do not ask a designer to draw to the 75% ceiling until you have separately checked the principal-dwelling footprint, detached-structure placement, lot coverage, drainage/stormwater, utility or septic capacity, and the parking interpretation DPZ will apply. The smallest of those constraints—not the headline 75% number—can become the practical project limit.
- Confirm the zoning district. Verify that the proposed ADU form is allowed on your property.
- Establish the exterior footprint. Do not use total multi-story living area as a substitute for Howard County’s footprint calculation.
- Calculate the 75% ceiling. Then test that number against setbacks, lot coverage and site constraints.
- Check water and sewer or well and septic. Resolve capacity questions before committing to plans. If the property uses private systems, use our Maryland ADU Septic & Well Readiness Guide before final design.
- Review drainage. A new detached structure must demonstrate adequate water conveyance.
- Confirm parking directly with DPZ. The county webpage and final legislative record currently conflict.
- Plan for owner occupancy. The property owner must reside in one of the two dwellings.
- Do not plan on Airbnb or VRBO. ADU short-term rentals are prohibited.
- Budget for the permit sequence. Zoning approval comes before operation of the ADU and before a rental-license application when one is required.
Howard County ADU application documents and submission steps
Submitting from a phone: the county warns that payment opens in a new tab. After paying, return to the application tab and click Submit to send the form for review. Payment alone does not complete that step. See the official application instructions.
Application instructions and $25 fee rechecked October 18, 2026. This check does not resolve the separate parking or dwelling-type discrepancies.
The county application instructions require a plot plan showing the proposed ADU meets size and setback limits. For a newly constructed structure, the plan must also address water conveyance and effects on neighboring properties or subdivision stormwater facilities. The page lists a $25 application fee.
- Prepare the required plot plan. Confirm the accepted size measurement and relevant setbacks with DPZ before finalizing it.
- Use the application linked by the county. Follow its current fields and attachment requirements.
- Complete both payment and submission. The county warns that mobile payment opens another tab. After paying, return to the form and click Submit. A payment alone does not complete that step.
- Keep the submission confirmation. Save the application reference, payment receipt and any requests for more information.
The county states that zoning approval must precede a rental-license application. It says a rental license is required to rent the primary dwelling or ADU. Check the separate construction and inspection requirements for your project as well.
Useful supporting records to have ready
Our suggested preparation folder includes the parcel identifier, existing survey or plat, floor plans, exterior dimensions, a description of the proposed dwelling arrangement, driveway and parking layout, and available utility records. This preparation list supplements the county instructions; it is not an assertion that every item is a mandatory attachment. Record missing evidence in the property feasibility checker.
Ask DPZ for a written parking determination
The county ADU portal still describes a three-space amendment, while Howard County Planning confirmed on September 29, 2026 that Section 128.0.A.13 is the current ADU regulation and that there are no current or proposed amendments to that section. Because the summary page and regulation presentation are not perfectly aligned, ask DPZ to identify the requirement it will apply to your parcel. Use this request with your site sketch:
I am considering an ADU at [property address and parcel identifier]. The principal dwelling is [dwelling type], and the proposed ADU is [attached, interior or detached]. Please confirm the current off-street parking requirement for this proposal, cite the controlling code section or enacted provision, and explain whether existing spaces count toward it. Please identify any applicable exception and the documentation needed to request it. Please also confirm that the proposed dwelling combination is eligible and identify any further review needed before I pay for final plans.
Submit the question through the county’s current Planning and Zoning contact channel. Keep the dated response and cited provision in your project folder. A preliminary response is not a permit approval; if it leaves the source conflict unanswered, request clarification before treating a parking layout as settled.
If this is your jurisdiction, stay focused on this county’s rules rather than comparing unrelated Maryland counties. Once the local rule path is clear, move through the project in this order:
- Check your property feasibility
- Estimate your allowable ADU size
- Build a realistic project budget
- Find professionals serving your area
Already ready to speak with a professional? Prepare a Maryland ADU project request →
Primary sources used for this Howard County guide
- Howard County Planning & Zoning — ADU portal
- Howard County Council — CB 3-2026 legislative record
- CB 3-2026 final amended text
- County Council February 2, 2026 session record
- Howard County ADU application
- Howard County Zoning Regulations — Section 128.0.A.13
For the full Maryland statewide framework, see our Maryland ADU Guide 2026. Maryland ADU Guide is maintained by Gijo John as an independent research publication. See our Editorial & Research Policy for how regulatory content is sourced and updated. Corrections supported by official records can be sent to gijo.j@marylandaduguide.com.
What to do next
Start by finding the office that reviews your property. A mailing city or a county guide does not establish your parcel’s authority.
- Find Who Reviews My Property.
- Obtain your parcel identifier, survey, floor plans and utility records.
- Ask the reviewing office which current rules, supporting documents and approvals apply.
- Continue to your planning workspace.
Enable JavaScript to prepare a downloadable next-step brief. Planning guidance is not permit approval.