State Guide · Verified 2026
Deck Construction Permits in Maryland
The only exception is a small freestanding platform 200 sq ft or smaller and no more than 30 inches above grade that is not attached to the house (IRC R105.2); any attached or elevated deck needs a permit.
The Building Code in Maryland
Maryland Building Performance Standards (MBPS), 2021 International Codes, adopted 2023, Building Codes Administration
The Building Codes Administration, within the Maryland Dept. of Labor, oversees the MBPS, based on the 2021 International Codes and adopted statewide in 2023. Maryland locks energy and accessibility code provisions, which no county can weaken, but leaves most other sections, including the specific deck permit threshold, open to local amendment. Baltimore County, under Council Bill 49-24 effective September 3, 2024, draws its permit line at 16 inches above grade for decks up to 120 square feet, well below the 30 inch figure common in most Maryland counties. Prince George's County requires decks to be self-supporting and freestanding, prohibiting ledger board attachment to the house for structural support, a local rule that diverges from both the IRC standard and most other Maryland counties. Every contractor performing deck work statewide must hold a Maryland Home Improvement Commission (MHIC) license.
Quick Facts
Who Sets the Rules
Baltimore County sets one of the strictest thresholds in this research
Where most US jurisdictions draw the deck permit line at 30 inches, Baltimore County draws it at 16, meaning a platform deck that would skip a permit almost anywhere else in the country needs one here, unless it stays under both 16 inches and 120 square feet.
A real structural prohibition, not just a stricter number
Prince George's County doesn't just tighten a threshold, it requires every deck to be self-supporting and freestanding, with all loads carried by posts on footings rather than a ledger board attached to the house, a genuine structural method prohibition that diverges from both the IRC standard and most other Maryland counties.
The Baltimore County exemption has real exceptions
Even under the 16 inch, 120 square foot threshold, the exemption disappears entirely in the Chesapeake Bay Critical Area, the floodplain, county historic districts, and properties on the Landmarks List, where every deck needs a permit regardless of size.
A statewide licensing floor that applies everywhere
Every contractor performing deck work anywhere in Maryland needs a valid Maryland Home Improvement Commission (MHIC) license, a genuine statewide requirement that provides a layer of consumer protection independent of which county's specific size threshold applies.
Baltimore City and Baltimore County are entirely separate systems
Baltimore City is an independent city, legally separate from Baltimore County, and the two run completely different permit systems, meaning a deck in Towson goes through the county while one in the city itself follows an entirely different process.
What people get wrong
The most common mistake is assuming Maryland's statewide MBPS framework means a single deck threshold applies everywhere. Only energy and accessibility provisions are genuinely locked; Baltimore County's 16-inch line and Prince George's County's ledger prohibition are both real, independent local decisions.
Counties With Their Own Rules
These Maryland counties have verified, county-specific deck construction rules that differ from the state baseline:
Check Your County
Select your county for the local rule, fees, and your building department's contact details:
Building It Yourself? Here's What You'll Need
Popular tools and materials homeowners use for a deck construction project:
As an Amazon Associate, we earn from qualifying purchases.
Official Sources
Rules change and cities within a county may differ. This guide is general information, not legal advice — always confirm with your local building department. Reviewed by the StateDataIndex Editorial Team · Updated September 2026.