What's Required in Baltimore
- Permit required for additions or conversions to independent dwelling units.
- Must meet new Maryland state ADU guidelines as of October 2025.
- Full construction plans signed and sealed by a MD design professional.
- Site plan required to show placement relative to main home.
- Must include independent living, cooking, and sleeping areas.
- Electrical, plumbing, and mechanical permits are mandatory.
How Much Does an ADU Permit Cost in Baltimore?
Budget $500–$2,000 for the Baltimore permit itself (valuation-based), issued by the Department of Permits, Approvals and Inspections — but treat that as the entry fee, not the total. ADUs are full dwelling units, so the permit stack usually includes building, electrical, plumbing, and mechanical trade permits, plus plan review. One local note: new ADU state laws effective 2025; local rules must align by Oct 2026. Get an itemized fee estimate from the department before finalizing your budget; the spread between a simple conversion and a new detached build is wide.
ADU Size Limits and Zoning Rules in Baltimore
Before drawing plans, check the two gates that sink most ADU projects: size and zoning. Size ceilings vary by lot and ADU type (attached, detached, or conversion), so confirm your specific configuration. Setbacks, height limits, and utility connections layer on top of those rules. The Department of Permits, Approvals and Inspections can confirm what your specific lot allows — worth doing before you pay for architectural drawings rather than after.
How to Get a ADU Permit in Baltimore
Step 1: Site Evaluation
Confirm lot has a single-family detached dwelling.
Step 2: Professional Plans
Have signed/sealed plans prepared by a Maryland architect.
Step 3: Submit Online
Apply via the PAI portal for a residential building permit.
Step 4: Technical Review
County reviews for zoning, building code, and utilities.
Step 5: Impact Fees
Pay calculated fees, including any applicable development impact fees.