Sumter, SC Crawl Space Guide: Code, Permits (2026)

Updated October 23, 2026. This guide is general information, not legal or engineering advice. Rules change, so confirm with the agency listed before you start work.

Quick reference

Topic	What to know	Source
Climate	Humid subtropical; 48.83 inches of precipitation a year (1991 to 2020 normals)	Wikipedia (NOAA normals)
2015 flood	20.77 inches in Sumter and 19.81 inches at Shaw AFB, October 2 to 6, 2015	NWS Columbia
Soils	Mimms and Scapo series, both first described in Sumter County: flood plain soils, water table 0 to 12 inches down, November to May	USDA NRCS
Building code	2021 IRC with SC modifications, enforced since January 1, 2023	SC LLR Building Codes Council
Builder license	Residential builder license for jobs over $5,000	S.C. Code 40-59-20
Specialty registration	Residential specialty contractors register for work over $500	S.C. Code 40-59-20; SC LLR
Sealed crawl space	Ground cover lapped 6 in. and sealed, 6 in. up the wall, plus exhaust, conditioned air or dehumidification	IRC R408.3
Permits	Sumter City-County Building Inspection Department for the city, county, Mayesville and Pinewood	City of Sumter permit form
CL-100 moisture	Excessive moisture at wood readings of 20% or more, or standing water; decay fungi active at 28% and above	S.C. Code Regs. 27-1085

Why do crawl spaces in Sumter County get damp?

Sumter's climate is humid subtropical, with long, hot summers and about 48.8 inches of precipitation in an average year. The U.S. Department of Energy points out that in humid climates the outside air is often wetter than the air in a crawl space, so foundation vents can bring moisture in. The ground contributes too. Two USDA soil series were first described from Sumter County sites: Mimms, near Lynches River Road (SC 341), and Scapo, in a swamp south of US 378 on the Mayesville quadrangle. Mimms is poorly drained and Scapo is very poorly drained. Both are flood plain soils with a seasonal high water table 0 to 12 inches below the surface from November through May. Sumter County is drained by the Black River and its tributaries, and the Wateree River forms its western border.

Heavy rain adds to it. During the October 2015 flood, the National Weather Service listed Sumter County among the areas with the heaviest rain. A CoCoRaHS gauge in Sumter recorded 20.77 inches through October 6, and the Shaw AFB station measured 19.81 inches.

What does South Carolina's building code say about crawl spaces?

The South Carolina Building Codes Council adopted the 2021 International Residential Code with state modifications, and local jurisdictions have been required to enforce it since January 1, 2023. IRC section R408 covers crawl spaces:

Vented crawl spaces need at least 1 square foot of net vent area per 150 square feet of floor, or 1 per 1,500 square feet when the ground has a Class I vapor retarder, with a vent within 3 feet of each corner.
Unvented crawl spaces need a continuous vapor retarder over the soil with seams lapped 6 inches and sealed, extending at least 6 inches up the wall, plus one air option: continuous exhaust or conditioned supply air at 1 cfm per 50 square feet, or a dehumidifier sized at 70 pints a day per 1,000 square feet.
Access openings must be at least 18 by 24 inches through a floor or 16 by 24 inches through a wall.

Building America research for DOE found that unvented, conditioned crawl spaces lowered heating and cooling energy use by 15 to 18 percent and reduced humidity by more than 20 percent in the homes studied.

Who needs a license for crawl space work in South Carolina?

SC LLR's Residential Builders Commission regulates home improvement contractors. Under S.C. Code section 40-59-20, a residential builder license is required when a job costs more than $5,000, and a residential specialty contractor has to register when the work costs more than $500. LLR caps a specialty registration at three classifications, such as carpentry, insulation or masonry, and a specialty contractor working directly for an owner on a job over $5,000 must be bonded. Contracting without the required license or registration is a misdemeanor. Limited exemptions exist for owners working on their own homes for their own use.

How do permits work in Sumter?

Sumter has a joint building department. The one- and two-family dwelling permit application from the Sumter City-County Building Inspection Department lists four jurisdictions: the City of Sumter, Sumter County, Mayesville and Pinewood. The form asks for the contractor's license number and each subcontractor's state license number, and it says every subcontractor needs a City of Sumter business license. The department accepts inspection requests only from the contractor of record, and an owner can't request inspections for a general contractor. Sumter County says permit requests go through a zoning check and a contractor licensing check before approval. Manning is in Clarendon County, so permits there go through a different office.

What is a CL-100, and why does it matter?

The CL-100, or Official South Carolina Wood Infestation Report, is part of most home sales in the state, and lenders commonly require one before closing. A licensed pest control company completes it. It covers termites, other wood-destroying insects and decay, and it includes crawl space moisture readings.

South Carolina Regulation 27-1085 sets the moisture standards. The inspector takes representative wood moisture readings around the inside perimeter of the crawl space and in the reachable center, and lists them with any decay, active decay fungi or excessive moisture. Excessive moisture means wood readings at or above 20%, or standing water in the crawl space or around the foundation. The regulation says wood-decay fungi become active and decay damage occurs at 28% and above. It names a polyethylene vapor barrier or added foundation vents as the usual correction, allows a sump pump only with a drain or trench system feeding it, and bars fungicide sprays on the substructure until the moisture problem is physically fixed.

Clemson University's Department of Pesticide Regulation licenses pest control companies and lets homeowners check an applicator's license.

What should you ask a crawl space company?

Which SC LLR license or registration do you hold, and under what name?
Is the moisture coming from rain, groundwater or humid air?
Does this job need a permit, and will you pull it as contractor of record?
Which liner, dehumidifier or supports are you proposing, and why those?
How will pest inspectors and repair crews get in afterward?
What's covered by the warranty, for how long, and what would void it?

Common questions

Does a crawl space contractor need a South Carolina license?

For most jobs, yes. SC LLR's Residential Builders Commission requires a residential builder license for work over $5,000 and a specialty contractor registration for specialty work over $500.

Which building code covers crawl spaces in Sumter?

The 2021 International Residential Code with South Carolina modifications, which local jurisdictions have enforced since January 1, 2023. Section R408 covers crawl spaces.

Who issues building permits in Sumter County?

The Sumter City-County Building Inspection Department, which handles the City of Sumter, unincorporated Sumter County, Mayesville and Pinewood.

Sumter crawl space guide (2026)