Side by side · South Carolina
Compare ADU rules across South Carolina
Flexible on where you build? The same backyard cottage can be routine in one city and impossible in the next. This table puts 20 South Carolina cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.
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| City | Detached ADU | Attached / internal | Max size | Owner occupancy | Extra parking | Approval |
|---|---|---|---|---|---|---|
| Aiken | Allowed | Allowed | Detached: 35% of the principal dwelling's gross heated floor area; attached (internal): no percentage cap; 450 sq ft minimum for either | Required | 1 additional off-street space | Permitted use |
| Beaufort | Allowed | Allowed | 50% of the primary building's footprint or 1,500 sq ft, whichever is smaller (min. 240 sq ft); max. 2 bedrooms | Not required | 1 off-street space per ADU (the 2025 citywide parking table lists 1.75 for a 2-bedroom accessory unit) | Permitted use |
| Bluffton | Allowed | Allowed | 1,200 heated sq ft and an 800 sq ft footprint (porches excluded); height two stories or the primary structure's height, whichever is less | Not required | 1 space per ADU (in addition to 2 per principal dwelling) | Permitted use |
| Charleston | Allowed | Allowed | 850 sq ft conditioned floor area; 600 sq ft footprint when the accessory building uses the 3 ft side/rear setback exception; 1,500 sq ft heated area in agricultural districts | The recorded Declaration of Covenants and Restrictions must state that either the principal dwelling or the ADU is owner-occupied as the owner's primary dwelling; if neither unit is owner-occupied, the ADU may not be rented separately from the principal dwelling. In practice owner residence is an ongoing, recorded condition for renting the ADU as a separate unit, enforceable by the city including by revoking the certificate of occupancy; an absentee owner may only rent the two units together. South Carolina has no state law overriding this. Ordinance read October 2026 | 1 additional off-street space | Permitted use |
| Charleston County | Allowed | Allowed | Rural Area: 1,500 sq ft heated; Urban/Suburban Area: no fixed cap (a detached ADU must be smaller than the house); overlays 600 to 1,500 sq ft; height up to the district maximum | Not required | No ADU-specific requirement; staff assign spaces by analogy (single-family dwellings need 2 per unit) | Permitted use |
| Columbia | Allowed | Allowed | Lesser of 1,000 sq ft or 50% of the principal dwelling's floor area (carports, garages, unfinished basements excluded) | Required | 1 additional off-street space | Permitted use |
| Florence | Allowed | Allowed | Detached: lesser of 50% of the principal structure's footprint or 1,000 sq ft. Attached: lesser of 35% of the principal structure's total floor area or 800 sq ft. No taller than the principal building; max 30% of the rear yard. | Required | None specified (former 1 space per bedroom rule repealed in 2025) | Permitted use |
| Goose Creek | Allowed | Allowed | 1,200 sq ft or 50% of the principal dwelling's floor area, whichever is less | Not required | None | Permitted use |
| Greenville | Allowed | Allowed | 80% of the primary dwelling, up to 1,000 sq ft; accessory structures 2 stories / 25 ft in RH-A, 2 stories / 20 ft in RH-B, RH-C and RH-D | Required | 1 space per ADU (on top of 2 per primary unit); waived in the Preservation (-P) overlay and on historic properties | Permitted use |
| Greenville County | In zoned unincorporated Greenville County a detached accessory dwelling is allowed only in the AG, Agricultural Preservation District, whose minimum lot area is 5 acres: Table 6.1 lists 'Dwelling - accessory' as C9 in AG, and condition 9(B) allows 'only one detached accessory dwelling unit' with a principal dwelling there. No single-family residential district (R-R3, R-R1, R-S, R-20 through R-6, R-20A, ESD-PM) lists the use. The only route on an ordinary residential lot is a temporary accessory dwelling under Section 11:9: a manufactured home approved by the Board of Zoning Appeals as a special exception for a relative needing continuous nursing care, renewed yearly and removed when the hardship ends. The 2024 Unified Development Ordinance that would have opened ADUs more widely was reconsidered in January 2025 and never took effect, so the 2005 Zoning Ordinance governs. Greenville County Zoning Ordinance, Table 6.1 ('Dwelling - accessory', C9 in AG) and Section 6:2(9)(B); Table 7.1 (AG minimum lot area 217,800 sq ft); Section 11:9 (Temporary Accessory Dwelling); as amended through 10-6-2026Full rules for Greenville County Ordinance read October 2026 | The Zoning Ordinance has no attached or internal ADU for houses in residential districts. Condition 9(A) allows one accessory dwelling inside the structure of a permitted nonresidential use in the O-D, C-1, C-2 and C-3 districts (a caretaker-type unit 'necessary to the operation of the permitted principal use'), and condition 9(B) in AG covers detached units only. The nearest by-right path to a second unit in a house is a two-family dwelling: a duplex is permitted on an existing lot of record in R-6, R-7.5 and R-10 if it meets the single-family district standards (condition 10(B), amended by Ord. 5807 of 9-15-2026), and outright in the R-M multifamily districts. Following the directory convention for codes without an attached ADU use, this is recorded as conditional with low confidence. Greenville County Zoning Ordinance, Section 6:2(9)(A) and (B); Table 6.1 ('Dwelling - two-family (duplex)'); Section 6:2(10)(B); as amended through 10-6-2026Full rules for Greenville County Ordinance read October 2026 | 50% of the primary dwelling's gross square footage (AG detached units); no fixed square-foot cap | Not required | None specified for the ADU (the house needs 2 spaces; AG ADU must share the house's driveway) | Permitted use |
| Hilton Head Island | Hilton Head Island's Land Management Ordinance (LMO) has no accessory dwelling unit use. Since Ord. 2023-06 (5-2-2023), 'More than one single-family dwellings on a single lot constitutes a multifamily dwelling', so a backyard cottage is legal only where Multifamily is a permitted use and the lot has density for a second unit. The use table permits Multifamily in RM-4, RM-8 and RM-12 and most mixed-use districts, but not in the RSF-3, RSF-5 and RSF-6 single-family districts, which allow Single-Family only. In the ten PD-1 plantations (Sea Pines, Hilton Head Plantation, Palmetto Dunes and others) uses and densities follow each Town-approved Master Plan, and private covenants usually govern as well. In the Gullah historic neighborhoods, a qualifying family can also place several homes on one parcel as a Family Compound. LMO §16-10-103.A.2 (Single-Family and Multifamily definitions); Table 16-4-102.A.6; §16-3-104Full rules for Hilton Head Island Ordinance read October 2026 | An internal or attached second unit (basement apartment, addition, garage apartment) makes the building one 'containing two or more dwelling units', which is the LMO's Multifamily use. It is therefore permitted only in the districts that allow Multifamily (RM-4, RM-8, RM-12 and most mixed-use districts) and only where density allows a second unit. It is not permitted in RSF-3, RSF-5 or RSF-6. The accessory use table lists no dwelling of any kind. Ord. 2023-06 also struck the only accessory dwelling use the LMO had, 'divisible dwelling units' (lock-out rooms), which had been limited to multifamily and interval occupancy developments in the CR and RD resort districts. LMO §16-10-103.A.2 (Multifamily definition); Table 16-4-102.A.6; Table 16-4-103.D.2; Ord. 2023-06Full rules for Hilton Head Island Ordinance read October 2026 | No ADU size cap; a second unit is a full dwelling unit counted against district density (RM-4: 4 du per net acre, 6 at 3+ acres, 8 at 5+ acres; RM-8: 8 du; RM-12: 12 du); height 35 ft in RM-4, 45 ft in RM-8 and RM-12 | Not required | Yes: a second unit is parked as multifamily, 1.4 spaces (1 bedroom), 1.7 (2 bedrooms) or 2 (3+ bedrooms) per unit; Family Compound units 2 per unit | Permitted use |
| Horry County | A detached ADU (a separate structure) is a conditional use in every zoning district where a single-family detached house is permitted, one per parcel, but the lot must be at least twice the district's minimum lot area and the unit must sit at least 20 feet from the house. Because most subdivision lots are platted near the minimum (6,000 square feet in SF6, 7,000 in SF7, 8,500 in SF8.5), a detached unit typically needs 12,000 to 17,000 square feet or more, so the lot-size gate excludes most suburban lots while larger rural and agricultural parcels qualify. Approval itself is administrative (see permit type). Horry County Zoning Ordinance (Code of Ordinances App. B) §925 and §925(C); Table 2-1 (§205)Full rules for Horry County Ordinance read October 2026 | Allowed | No ADU-specific size cap; one ADU per parcel, district setbacks, height (typically 35 ft) and lot coverage apply | Required | 2 spaces for the ADU (treated as a single-family unit) in addition to the house's 2 | Permitted use |
| Lexington County | The Lexington County Zoning Ordinance has no accessory dwelling unit use; a second detached home is simply another principal dwelling (a site-built Residential Detached unit, a Tiny Home of about 400 square feet or less, or a Mobile Home), and the ordinance regulates how many homes a parcel may hold through density rather than a one-house-per-lot rule. Residential Detached is listed in every district, and Section 22.30 caps density at 2 dwelling units per acre in R1, D and RA, 3 in R2 and 4 in R3 (4 is also the countywide ceiling), with the street classification cap applying when it is lower (1 per acre on Residential Local One and Two streets). In practice a second house needs roughly 1 acre in R1, D or RA, two-thirds of an acre in R2, half an acre in R3 or the commercial districts, and 2 acres on an RL1 or RL2 street, which rules out most suburban lots. Secondary units are barred outright in Residential Detached (Limited) patio-home developments, and a pre-existing undersized lot may support only one dwelling. Lexington County Zoning Ordinance §§21.10 (Residential Detached, Tiny Home, Mobile Home), 21.31, 22.30, 22.40 and 122.11 (compiled through Ord. 26-03, June 23, 2026)Full rules for Lexington County Ordinance read October 2026 | There is no attached or internal accessory unit use. A second unit inside or attached to a house makes the building a Residential Attached - Duplex (two dwelling units in one structure separated by a common wall), which Section 21.31 allows only in R3, RD, C1, C2, ID and LR, not in the R1, R2, D or RA districts that cover most single-family land. Duplexes also need a street classification that allows them (Arterial, Collector, Local, RL6, RL5 or Boulevard, not RL4, RL2 or RL1) and must meet the same Section 22.30 density as detached homes. The ordinance's definition of attached also sweeps in units joined to the house by a covered walkway. Lexington County Zoning Ordinance §§12.10 (Attached), 21.10 (Residential Attached - Duplex), 21.31, 22.02, 22.30Full rules for Lexington County Ordinance read October 2026 | No ADU size cap; a Tiny Home is 400 sq ft or less (lofts excluded); a second site-built house is limited only by setbacks, height and density | Not required | 3 spaces per added detached house; 2 per tiny home, mobile home or duplex unit | Permitted use |
| Mount Pleasant | Allowed | Allowed | Attached or internal: 850 sq ft gross floor area. Detached: footprint cap of 850 sq ft (CC, R-1, R-2 and other districts), 600 sq ft (R-3, R-4, TH, RM), no cap in RC-1, RC-2, RR beyond building coverage; 25 ft height (29 ft or principal height in the Old Village) | Required | 1 additional off-street space | Permitted use |
| Myrtle Beach | Not allowed | There is no attached ADU or accessory apartment either, but a second unit inside or attached to a house is possible as a two-family dwelling (duplex) in the districts that allow one: permitted by right in RMM, RMH, RMH-MH, RMV, MU-M, MU-H, C7, C8, A, E, HC2, MP and IN, and as a conditional use in C6 and HC1. In RMM, RMH and RMH-MH the second unit needs 2,000 square feet of lot area beyond the 4,500 for the first. The ordinary single-family districts (R5 through R15), which cover most neighborhoods, allow no second unit at all. Appendix A §§ 1407.C (Permanent residence, two-family dwellings), 1603.C and 1603.D, 203 (Dwelling, Two-family (duplex))Full rules for Myrtle Beach Ordinance read October 2026 | No ADU size cap (no ADU use). A duplex follows district standards: RMM/RMH 5,000 sq ft min. lot, 35 ft height, 42% coverage; second unit needs 2,000 sq ft of extra lot area | Not required | No ADU standard. Single-family: 2 spaces per unit; two-family: 1 space per 600 sq ft of gross floor area, max. 3 per unit | Permitted use |
| North Charleston | Allowed | The ADU provisions cover only detached units: §3-2 defines an accessory dwelling unit as 'a separate, detached dwelling unit', so an internal or attached apartment in a single-family home in R-1 is not an ADU and has no permit route there. A second unit inside or attached to a house is possible only as a duplex, which is a permitted use in the R-2 Multi-Family district (and in R-3, which allows all R-2 uses), subject to the R-2 lot area of 1,500 square feet per multi-family unit. In the Olde North Charleston overlays the only accessory unit form named is an apartment over a detached garage. North Charleston Zoning Regulations §3-2 'Dwelling unit, accessory'; §5-2(a)1; §5-2.1(a)1; §6-1(a)2Full rules for North Charleston Ordinance read October 2026 | Two-thirds of the principal dwelling, max 800 sq ft; height no taller than the house (24 ft to ridge over a detached garage when the house is one story); 4,500 sq ft minimum lot | Not required | 1 additional off-street space | Permitted use |
| Richland County | Allowed | Allowed | 750 sq ft or 25% of the principal dwelling's heated floor area, whichever is greater; detached accessory structures also count toward the residential cap of 50% of principal GFA or 1,200 sq ft (whichever greater); height up to the district's principal-building limit | Not required | None specific to the ADU (the single-family dwelling needs 2 spaces) | Permitted use |
| Rock Hill | Allowed | Allowed | No ADU-specific cap; at least 480 sq ft. A detached ADU counts toward the combined limit on all detached accessory structures: the greater of 30% of the house's heated floor area or 600 sq ft (house with a two-car garage or carport), 800 sq ft (one-car garage) or 1,000 sq ft (no garage), with 200 or 400 sq ft of the larger allowances reserved for a detached garage. Height: the lesser of two stories or the height of the house. | Required | 1 off-street space per ADU bedroom | Permitted use |
| Spartanburg | Only the Downtown Code allows a second dwelling on a house lot: its use table lists 'Dwelling-Secondary' as permitted in D-T4 (General Urban) and permitted subject to supplemental standards in D-T5 (Urban Center), and not in D-T3 or D-T6. In the ordinary residential districts (R-15, R-12, R-8 SFD, R-8 General, R-6) the Zoning Ordinance has no accessory dwelling use, Section 501.1 prohibits unlisted uses and Section 501.2 allows no more than one principal residential building per lot, and planning staff told the Board of Zoning Appeals in September 2026 that a new ADU or a garage conversion is not permitted in those districts. ADUs that predate the 1999 ordinance survive as nonconforming uses. Downtown Code (Zoning Ordinance Appendix A) §§3.1.3, 3.2.3; Zoning Ordinance §§302.1 to 302.5, 501.1, 501.2Full rules for Spartanburg Ordinance read October 2026 | The Downtown Code defines a secondary dwelling as 'either detached or non-detached', so an attached unit is allowed in D-T4 and D-T5 on the same terms as a detached one (rear yard, one per lot). Elsewhere there is no accessory unit, but the R-12, R-8 General and R-6 districts allow two-family dwellings by right, so a house there can become a duplex if it meets the two-family lot area, yard and two-spaces-per-unit parking rules; R-15 and R-8 SFD allow single-family dwellings only (plus boarders or lodgers without a separate unit). Downtown Code Definitions ('Dwelling - Secondary') and §3.2.3; Zoning Ordinance §§302.2.A.2, 302.3, 302.4.A.2, 302.5.A, 401(A)Full rules for Spartanburg Ordinance read October 2026 | 25% of the principal structure's gross floor area (500 sq ft minimum habitable area); definition caps it at 750 sq ft; 2 stories and no taller than the house (D-T4/D-T5 only) | Not required | 1 space per secondary dwelling (D-T4/D-T5), in the rear or side yard or on-street in front of the house | Permitted use |
| Summerville | Allowed | Allowed | 50% of the primary building's gross floor area; 2 bedrooms; 2 adult residents; detached accessory buildings 20 ft high in N-R and N-MX, no taller than the main house in the GR districts | Required | 1 space per ADU (none in D-MX); at most 2 spaces per ADU | Permitted use |
Summarized from each city's ordinance text, most recently read October 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.
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Reading the table
- Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
- Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
- Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.
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