Why it matters to you
Lowcountry boundaries interleave: a James Island address may fall under the City of Charleston or unincorporated Charleston County, and parts of Summerville reach into three counties. Your AHJ sets the procedures and fees for your project, and downtown it can add preservation review on top of the mechanical permit.
Practical guidance
Look up your parcel on your county's GIS viewer to see which municipality covers it, and expect your contractor to confirm the jurisdiction during permitting. A bidder who is vague about which building department covers your address is a small red flag.
