Mount Pleasant, SC Accessory Structures: ADU Rules (2026)
ADU rules in Mount Pleasant, SC, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Max ADUs
- One per lot
- Attached/internal size cap
- 850 square feet gross floor area
- Detached size cap
- Set by Table 156.424-2 footprint table
- Parking
- One dedicated off-street space required
- Permit
- Zoning permit plus site plan checklist
Summary
The Town of Mount Pleasant allows one accessory dwelling unit per lot under § 156.445 of the zoning code. Detached ADUs are capped by the town's accessory-building footprint table, attached or internal ADUs are limited to 850 square feet, and each ADU needs its own dedicated off-street parking space plus a zoning permit.
§ 156.445 ACCESSORY DWELLING UNIT. ... (A) Purpose. ... This section is intended to encourage accessory dwelling units (ADUs) as an alternative housing choice. (B) Maximum number of accessory dwelling units per lot. A maximum of one ADU per lot is allowed, subject to building coverage requirements. (C) Maximum size. ... (2) Attached ADUs and ADUs located within a principal structure are limited to a maximum of 850 square feet in gross floor area. (D) Parking. (1) One private, off-street parking space is required for use by occupants of each accessory dwelling unit, in addition to any and all spaces required for the principal structure.
Full Breakdown
445 of Mount Pleasant's zoning code, adopted to encourage accessory dwelling units "as an alternative housing choice," sets the town's core ADU standards. Subsection (B) caps every lot at a maximum of one ADU, subject to the property's building coverage requirements. 424-2 (Maximum Footprint of Accessory Buildings), while an attached ADU, or one built within the principal structure, is limited to 850 square feet of gross floor area. Subsection (D) requires one private, off-street parking space dedicated to the ADU's occupants, in addition to whatever parking the principal dwelling already requires, with that space clearly shown on the site plan; tandem parking is barred unless the tandem spaces serve only the ADU.
Subsection (F) requires a zoning permit application under Subchapter I, Part 7, including a scaled site plan meeting the Accessory Dwelling Unit Site Plan Checklist issued by the Department of Planning, Land Use, and Neighborhoods. 436, which first authorizes ADUs as an accessory use tied to a detached house dwelling.
Violations & Fines
Building or occupying an ADU that exceeds the one-per-lot limit, the size caps in § 156.445(C), or the dedicated-parking requirement in § 156.445(D), or that skips the required zoning permit, is a zoning violation enforced by the Planning, Land Use and Neighborhoods Department. Chapter 156 does not set a separate fine for this section, so the Town's general penalty at § 10.99 applies: up to a $500 fine, up to 30 days imprisonment, or both, with each day of a continuing violation a separate offense, and the condition may be abated as a public nuisance.
Frequently Asked Questions
How many ADUs can I build on one lot in Mount Pleasant?
How big can an ADU be in Mount Pleasant?
Does an ADU need its own parking space?
Sources & Official References
Other rules in Mount Pleasant
How Mount Pleasant compares: Easiest Cities to Build an ADU·Compare Mount Pleasant to another location·View the South Carolina accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
ADU Rules in Nearby Cities
How other cities in Charleston County handle adu rules.