Do I need a permit for deck construction or replacement in Unincorporated Calvert County?

Most likely yes. Deck construction or replacement usually requires a permit in Maryland. Confirm the specifics with Unincorporated Calvert County.

Maryland made no State change to the 2021 IRC list of work exempt from permit, so the model deck exemption (not over 200 sq ft, not over 30 inches above grade, not attached, and not serving the required exit door) is the starting point; most attached or raised decks fall outside it. Local jurisdictions may amend the Standards, and a local amendment prevails where it conflicts (Public Safety 12-504); the county, Baltimore City, or a municipality with its own code office sets the actual permit list. Land within 1,000 feet of tidal waters or tidal wetlands is generally in the Chesapeake Bay or Atlantic Coastal Bays Critical Area, where State law caps lot coverage (often 15 percent, or 25 percent on some older small lots) and a separate local critical area review may apply. This deck is attached to the house or will have a roof. Where a small deck exemption exists at all, it covers only small, low, freestanding decks that do not serve the home's required exit door, so an attached deck falls outside it. A ledger bolted to the house is the most common point of deck failure, which is why departments inspect the footings, framing and ledger connection before the decking goes on. Adding a roof makes the deck a covered structure that is reviewed like a patio cover or addition, including roof framing and, in high wind areas, uplift connections.