Yes. Charleston lets you build one accessory dwelling unit of up to 850 sq ft of conditioned floor area on any lot with a single-family house, in every base zoning district (Zoning Ordinance Sec. 54-214, Ord. 2020-116 as amended by Ord. 2022-069). Approval is administrative: the Zoning Administrator signs off on a site plan at the Permit Center, with no public hearing and no Board of Zoning Appeals step. You need one extra off-street parking space and a recorded covenant that requires owner-occupancy of the house or the ADU, caps ADU occupancy at two adults and bans short-term rental of either unit. City permit fees for an 850 sq ft unit run roughly $700-$1,300; in a flood zone the unit must sit 2 ft above base flood elevation on a non-slab foundation.
Zoning & Size Requirements [1][2][3][4][5]
Yes — Charleston allows ADUs. A detached ADU can typically be up to 850 sq ft under current South Carolina and Charleston zoning rules.
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| Allowed Zones | All base zoning districts, as an accessory use to a principal single-family dwelling, approved by the Zoning Administrator when the Sec. 54-214 conditions are met (Ord. 2020-116, rewritten by Ord. 2022-069); no BZA hearing. The lot must not carry a recorded covenant prohibiting ADUs, and the owner certifies this on the application (SC Code 6-29-1145). In Board of Architectural Review districts, exterior design needs a Certificate of Appropriateness first. |
| Max Size (Detached) | 850 sq ft of conditioned floor area (Sec. 54-214.e). If the accessory building uses the reduced side/rear setback exception in Sec. 54-506(f), its building footprint is capped at 600 sq ft instead. |
| Max Size (Attached) | 850 sq ft of conditioned floor area; the same cap applies whether the ADU is inside the principal house or in a detached accessory building (Sec. 54-120 definition, Sec. 54-214.e). Two dwelling units per lot maximum. |
| Max Size (JADU) | No JADU category in South Carolina or in Charleston's ordinance; the 850 sq ft ADU standard is the only path, and an ADU carved out of the main house counts against the same cap. |
| Max Height | No ADU-specific limit; the base district's height standard governs, and the site plan must show height to the eave and to the roof peak (ADU checklist, March 2026). An accessory building using the Sec. 54-506(f) reduced setback carries that exception's own lower height cap; confirm the current figure with the Zoning Desk (843-724-3765). |
| Max Units | 1 ADU per lot and 2 dwelling units per lot in total (house + ADU); ADU occupancy is limited to 2 adults (18+) plus any children; the property may not be converted to a horizontal property regime (condo); separate electric, gas and water meters are allowed (Sec. 54-214.c-d and g). |
Setback Requirements [1][2][3][4][5]
Charleston requires a rear setback of about 3 ft for a detached ADU, and one off-street parking space is required. Owner-occupancy is required.
| Rear Setback | The district's accessory-building rear setback applies. Sec. 54-506(f) lets a qualifying accessory building with a footprint of 600 sq ft or less sit closer to an interior rear line (3 ft as read from the code in July 2026; Municode could not be re-read on Sept. 20, 2026, so confirm the distance and which lot lines qualify with the Zoning Desk). |
| Side Setback | District standard; the same Sec. 54-506(f) exception (600 sq ft footprint cap) applies to interior side lines, distance to be confirmed with the Zoning Desk. If any part of the ADU is within 15 ft of a property line, the site plan must also show the principal buildings on the adjoining lots (ADU checklist, March 2026). |
| Front Setback | District front setback applies in full; Sec. 54-506(f) only relaxes interior side and rear setbacks. Easements, buffers and the OCRM critical line and its setback must be drawn and labelled on the site plan. |
| Parking Required | 1 off-street space for the ADU on top of the 2 required for the single-family house, all on the same lot; tandem parking allowed; each space 9 ft x 18.5 ft and the ADU space must be labelled on the site plan (Sec. 54-214.f; Permit Center ADU page). |
| Owner Occupancy | Required. Either the house or the ADU must be the owner's primary residence; if neither is owner-occupied the ADU may not be rented separately from the house. This is written into a recorded Declaration of Covenants and Restrictions (DCR) that runs with the land, bars subleases, and lets the city revoke the certificate of occupancy to enforce it (Sec. 54-214.g). |
| Min Lot Size | No ADU-specific minimum lot size. The lot must hold a conforming single-family dwelling, and the ADU must fit inside the district's setbacks and building-coverage limit (the site plan must state lot area and the coverage calculation). |
Permit Process & Fees [6][7][8][9][10]
An ADU permit in Charleston goes through a standard permit review. Review time: not published. Zoning Desk review of the ADU application and DCR comes first, then building plan review (the fee covers the initial review plus one follow-up); allow several weeks to a few months, longer with BAR review or a flood-zone foundation design. Permit fees: Valuation-based (fee schedule eff. Oct. 1, 2019): $40 application + permit fee ($260 + $4 per $1,000 over $50,000; $460 + $3 per $1,000 over $100,000) + plan review at 50% of the permit fee. An 850 sq ft ADU at the schedule's $116.15/sq ft is about $724 before trade permits; budget $700-$1,300.
| Approval Process | Staff-level, three steps: (1) ADU Application/Checklist (form dated 03/11/2026), scaled site plan, the owner's signed statement that no covenant prohibits an ADU, and a draft DCR to the Zoning Desk at the Permit Center, 2 George St; staff mark it Approved, Approved with conditions or Disapproved. (2) New Single-Family Building Permit application; construction may start when the permit issues. (3) Record the Planning- and Legal-approved DCR with the county Register of Deeds and file a copy at the Zoning Desk before the Certificate of Construction Completion; the ADU cannot be occupied until then. In BAR districts, get the Certificate of Appropriateness before step 2. |
| Review Timeline | Not published. Zoning Desk review of the ADU application and DCR comes first, then building plan review (the fee covers the initial review plus one follow-up); allow several weeks to a few months, longer with BAR review or a flood-zone foundation design. |
| Permit Fees | Valuation-based (fee schedule eff. Oct. 1, 2019): $40 application + permit fee ($260 + $4 per $1,000 over $50,000; $460 + $3 per $1,000 over $100,000) + plan review at 50% of the permit fee. An 850 sq ft ADU at the schedule's $116.15/sq ft is about $724 before trade permits; budget $700-$1,300. |
| Impact Fees | None listed on the city's Building and Trade Permit Fee Schedule. A separately metered ADU may trigger Charleston Water System tap and capacity charges; ask CWS and the Permit Center for current figures before you budget. |
| Plan Check | Plan review fee is 50% of the building permit fee and includes the initial review plus one follow-up; further re-reviews cost $100 per trade discipline. In the Special Flood Hazard Area the lowest floor must be 2 ft above Base Flood Elevation (new construction since July 1, 2020), slab-on-grade foundations are prohibited for permits applied for on or after Jan. 1, 2024, and an Elevation Certificate is required. |
| Pre-Approved Plans | No pre-approved plan program. Housing and Community Development's Affordable ADU grant offered $20,000 reimbursements to 10 selected homeowners in its March 2023 round; any city subsidy binds the ADU to 80%-AMI rents for at least 30 years (Sec. 54-214.g.3-4). Ask HCD whether a current round is open. |
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Construction Costs [11][12]
Building an ADU in Charleston typically costs $140,000-$300,000 ($225-$350 per sq ft); a garage conversion runs $60,000-$150,000.
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| Average Build Cost | $140,000-$300,000 |
| Cost per Sq Ft | $225-$350 |
| Garage Conversion | $60,000-$150,000 |
| Prefab ADU (Installed) | $100,000-$200,000 |
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Rental Income Potential [13][14]
A 2-bedroom ADU in Charleston rents for around $1,750-$2,000/mo, an estimated 5-8% annual return (long-term rental; market estimate).
| Avg Rent (1 Bedroom) | $1,550-$1,750/mo |
| Avg Rent (2 Bedroom) | $1,750-$2,000/mo |
| Short-Term Rental | No. The recorded DCR bars short-term rental of both the ADU and the main house, and the Permit Center states that lots with an ADU are not eligible for a Short-Term Rental permit (STR rules: Secs. 54-208.1-208.3). |
| Est. Annual ROI | 5-8% annual return (long-term rental; market estimate) |
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Recent Law Changes
What's Changed Recently
- September 20, 2026: entry re-verified against the ratified ADU ordinances (Ord. 2020-116, Sept. 8, 2020; Ord. 2022-069, May 10, 2022), the city's ADU Application/Checklist dated March 11, 2026, the Building and Trade Permit Fee Schedule and Housing and Community Development's 2025-2026 rent and income sheet. Status changed from 'discretionary' to 'allowed' because approval is by the Zoning Administrator on listed conditions with no hearing; the fee estimate was rebuilt from the official schedule.
- Ord. 2025-086 (June 17, 2025) was listed in the code history for Sec. 54-214 when the code was read in July 2026; its text could not be retrieved on Sept. 20, 2026 (Municode bot-walled, Wayback offline). The standards above match the 2022 ordinance text and the city's March 2026 application form; ask the Zoning Desk whether 2025-086 changed anything before relying on a detail.
- May 10, 2022: Ord. 2022-069 rewrote Sec. 54-214 so the 80%-AMI affordability covenant applies only to city-subsidized ADUs (with an affordability period of at least 30 years); market-rate ADUs carry no rent limit.
- SC H.3469 (Accessory Dwelling Unit Affordable Housing Incentive Act: a property-tax exemption for ADUs rented to households at or below 80% AMI for at least 10 years) has had no action since Feb. 5, 2025 in House Ways and Means and would need to be refiled in the 2027 session.
Tips for Building an ADU in Charleston
- Check your flood zone before anything else. Inside the Special Flood Hazard Area (A/AE/VE zones) the ADU's lowest floor must be 2 ft above Base Flood Elevation, slab-on-grade foundations have been prohibited since Jan. 1, 2024, and you need an Elevation Certificate; in Zone X none of that applies. The site plan must state the flood zone, so look it up on the FEMA map first.
- Read the covenant before you commit. The DCR requires owner-occupancy of the house or the ADU, bars subleases, caps ADU occupancy at 2 adults, forbids a condo split, bans short-term rental of BOTH units and lets the city revoke your certificate of occupancy; it runs with the land and binds every future buyer. Planning and the Office of Corporation Counsel must approve the draft before you record it.
- You must certify on the application that no recorded covenant prohibits an ADU on your lot (the form cites SC Code 6-29-1145). Many West Ashley, James Island and Daniel Island HOA covenants do prohibit them, so read yours before paying for drawings.
- Board of Architectural Review approval applies only in the city's designated historic and landmark districts (the peninsula's Old and Historic, Old City and related overlays) and to individually landmarked properties; a typical West Ashley or James Island lot outside those districts skips BAR. Confirm your parcel on the city zoning map (charleston-sc.gov/295/Zoning).
- Confirm which jurisdiction you are in first: pockets of the 29407 and 29412 ZIP codes are unincorporated Charleston County, where the county's Zoning and Land Development Regulations, not Sec. 54-214, govern and the size and lot rules differ. Check your TMS number on the county GIS before designing.
- Cost basis: the city's own March 2023 ADU webinar put construction at $225-$250 per sq ft plus about $15,000 of pre-development work (survey ~$800, geotechnical study ~$1,500, construction plans $12,000-$14,000), a $127,500 sample for 500 sq ft; the ranges here add 2024-2026 cost growth and, at the top end, a flood-elevated foundation.
- Fee worked example from the official schedule: $40 application + $456 permit + $228 plan review = $724 for an 850 sq ft ADU valued at the schedule's $116.15 per sq ft, before the electrical ($40 application plus fee), plumbing ($40 plus $3.50 per fixture) and mechanical permits. The Building Official sets valuation from current ICC data, so expect somewhat more.
- South Carolina's owner-builder exemption is meant for a home you will occupy, not for a unit built to rent or sell, so an income ADU generally needs a licensed residential builder; confirm with SC LLR before you plan to self-build.
- Taking the city subsidy means a 30-year affordability covenant at 80% AMI: at the city's 2025-2026 limits that is $62,160 income for a one-person household and a workforce 1-bedroom rent of about $1,554 a month, verified annually with Housing and Community Development.
- Cost basis (2026-09-20 re-verification): short term allowed: No. The recorded DCR bars short-term rental of both the ADU and the main house, and the Permit Center states that lots with an ADU are not eligible for a Short-Term Rental permit (STR rules: Secs. 54-208.1-208.3). Plan on tenants of 30 days or longer.
ADU Builders in Charleston
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Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Charleston Zoning Ordinance Sec. 54-214 - Accessory Dwelling Unit Planning Department — Accessed 2026-07-30
- Ord. 2022-069 amending Sec. 54-214 (ratified May 10, 2022) - Municode ordinance archive Planning Department — Accessed 2026-09-20
- Ord. 2020-116 creating Sec. 54-214 (ratified Sept. 8, 2020) - Municode ordinance archive Planning Department — Accessed 2026-09-20
- Charleston Zoning Ordinance Sec. 54-506 - Setback Exceptions Planning Department — Accessed 2026-07-30
- Backyard Homes (ADUs) - City of Charleston Planning Department — Accessed 2026-09-20
- Accessory Dwelling Unit (ADU) - City of Charleston Permit Center Planning Department — Accessed 2026-09-20
- ADU Application/Checklist (rev. 03.11.2026) - City of Charleston Planning Department — Accessed 2026-09-20
- Building and Trade Permit Fee Schedule (eff. Oct. 1, 2019) - City of Charleston Planning Department — Accessed 2026-09-20
- ADU Declaration of Covenant (no subsidy) - City of Charleston Planning Department — Accessed 2026-09-20
- Floodplain Development (2 ft freeboard, slab prohibition) - City of Charleston Planning Department — Accessed 2026-09-20
- Building a Backyard Home in Charleston - city ADU webinar slides (March 15, 2023) Planning Department — Accessed 2026-09-20
- Angi - ADU Construction Cost Data industry — Accessed 2026-07-30
- 2025-2026 Rental Rates and Income Limits (FMR, HOME, workforce) - City of Charleston HCD Government Data — Accessed 2026-09-20
- HUD Fair Market Rents, Charleston-North Charleston SC MSA Government Data — Accessed 2026-07-30
- Charleston Short Term Rental rules (Secs. 54-208.1-208.3) Planning Department — Accessed 2026-07-30
- SC Legislature H.3469 - ADU Affordable Housing Incentive Act (2025-2026) Government Data — Accessed 2026-09-20
Frequently Asked Questions
Can I build an ADU in Charleston?
Yes. ADUs are allowed in All base zoning districts, as an accessory use to a principal single-family dwelling, approved by the Zoning Administrator when the Sec. 54-214 conditions are met (Ord. 2020-116, rewritten by Ord. 2022-069); no BZA hearing. The lot must not carry a recorded covenant prohibiting ADUs, and the owner certifies this on the application (SC Code 6-29-1145). In Board of Architectural Review districts, exterior design needs a Certificate of Appropriateness first. in Charleston. The maximum size for a detached ADU is 850 sq ft of conditioned floor area (Sec. 54-214.e). If the accessory building uses the reduced side/rear setback exception in Sec. 54-506(f), its building footprint is capped at 600 sq ft instead.. Owner-occupancy is required: Required. Either the house or the ADU must be the owner's primary residence; if neither is owner-occupied the ADU may not be rented separately from the house. This is written into a recorded Declaration of Covenants and Restrictions (DCR) that runs with the land, bars subleases, and lets the city revoke the certificate of occupancy to enforce it (Sec. 54-214.g).
How much does an ADU cost in Charleston?
ADU construction in Charleston typically costs $140,000-$300,000. Garage conversions run $60,000-$150,000, and prefab ADUs cost $100,000-$200,000.
How much can I rent an ADU for in Charleston?
Average ADU rents in Charleston are $1,550-$1,750/mo for a 1-bedroom and $1,750-$2,000/mo for a 2-bedroom unit.
Do I need parking for an ADU in Charleston?
1 off-street space for the ADU on top of the 2 required for the single-family house, all on the same lot; tandem parking allowed; each space 9 ft x 18.5 ft and the ADU space must be labelled on the site plan (Sec. 54-214.f; Permit Center ADU page).. Check with Charleston planning department for the latest South Carolina ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Charleston?
Charleston does not publish a standard ADU review timeline. Zoning Desk review of the ADU application and DCR comes first, then building plan review (the fee covers the initial review plus one follow-up); allow several weeks to a few months, longer with BAR review or a flood-zone foundation design. Permit fees: Valuation-based (fee schedule eff. Oct. 1, 2019): $40 application + permit fee ($260 + $4 per $1,000 over $50,000; $460 + $3 per $1,000 over $100,000) + plan review at 50% of the permit fee. An 850 sq ft ADU at the schedule's $116.15/sq ft is about $724 before trade permits; budget $700-$1,300.
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