An ADU builder in Charleston is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Charleston's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in South Carolina.
What ADU Builders Cost in Charleston [11][12]
Based on our Charleston cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $140,000-$300,000 |
| Cost per Sq Ft | $225-$350 |
| Garage Conversion | $60,000-$150,000 |
| Prefab / Modular ADU (installed) | $100,000-$200,000 |
| City Permit & Plan Review | 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. |
For a full line-item breakdown, see our Charleston ADU cost guide. To confirm what you're allowed to build before you hire, review the Charleston ADU rules (max detached size: 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: 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).).
Get Free ADU Quotes in Charleston
Tell us about your project and we'll pass it to ADU builders serving Charleston. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
Takes about a minute.
Up to 5 independent local ADU builders — never more, and we tell them nothing you don't submit here.
Compare quotes, verify license & insurance, hire (or don't). No spam either way.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.
How to Vet an ADU Builder in Charleston
- License: Confirm a current contractor's license in South Carolina and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Charleston and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (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.), 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.), and 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.) are included.
- Permit handling: Confirm they manage Charleston's permit 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.", typically 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.) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Charleston in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (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.) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent South Carolina ADU client references?
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
Some links on this page are affiliate links. We may earn a commission at no extra cost to you. Learn more
Are you an ADU builder? Get Charleston leads
Homeowners on this page submit real ADU project requests in Charleston. Each one goes to up to five local builders — that is what the homeowner agrees to — so claiming never takes it from anyone and there is no bidding. In practice far fewer ever make contact, which is why the number is five rather than three. A flat $50 only on the leads you accept: no subscription, no contract, and you deal with the homeowner directly.
Get Charleston ADU Leads →Frequently Asked Questions
How much do ADU builders charge in Charleston?
How do I find a good ADU builder in Charleston?
Do ADU builders in Charleston handle permits?
How long does it take to build an ADU in Charleston?
Get Free ADU Builder Quotes in Charleston
Compare bids from experienced local Charleston ADU builders. Free, no obligation.
Get Free Quotes →