Florence, SC Crawl Space Guide: Code, Licenses (2026)

Updated October 22, 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; about 48.12 inches of precipitation a year (1991 to 2020 normals)	Wikipedia (NOAA normals)
Record rain	11.74 inches at Florence on October 8, 2016, during Hurricane Matthew	SC State Climatology Office
Soils	Rains series, first described near Timmonsville: poorly drained, water table 0 to 12 inches down, December to April	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 jobs over $500, up to three classifications	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	City of Florence Building Department in the city; Florence County Building Inspections in the county	City of Florence; Florence County
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(J)

Why do crawl spaces in Florence County get damp?

Florence has a humid subtropical climate and averages about 48 inches of precipitation a year. The U.S. Department of Energy notes that in humid climates outdoor air is often more moist than the air in a crawl space, so foundation vents can add moisture rather than remove it. The ground adds more. The USDA's official description of the Rains soil series is based on a site near Timmonsville, and it describes a poorly drained soil whose seasonal high water table can sit within a foot of the surface from December to April, on flats, depressions and Carolina bays. Storms add the rest: during Hurricane Matthew, Florence recorded 11.74 inches of rain in a single day.

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

South Carolina's 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. The City of Florence lists the 2021 IRC among its adopted codes. Section R408 of the IRC sets the main crawl space rules:

Vented crawl spaces need at least 1 square foot of net vent area for every 150 square feet of floor, or 1 per 1,500 square feet when the ground is covered with a Class I vapor retarder, with a vent within 3 feet of each corner.
Unvented crawl spaces need a continuous vapor retarder over the ground with seams lapped 6 inches and sealed, run at least 6 inches up the wall, plus one way of conditioning the air: 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 unvented, conditioned crawl spaces cut heating and cooling energy use by 15 to 18 percent and reduced humidity by more than 20 percent in homes studied.

Who needs a license to do crawl space work in South Carolina?

The Residential Builders Commission, part of SC LLR, regulates home improvement contractors. Under S.C. Code section 40-59-20, a residential builder license is needed when the cost of the job exceeds $5,000, and a residential specialty contractor must register when the work exceeds $500. LLR limits a specialty registration to three trade classifications, such as carpentry, insulation or masonry. A specialty contractor working for an owner on a job over $5,000 has to be bonded. Working without the required license or registration is a misdemeanor. There are limited exemptions for owners improving their own homes for their own use.

How do permits work around Florence?

Inside city limits, the City of Florence Building Department issues permits and inspects construction, including remodeling. In the unincorporated county, Florence County Building Inspections says a permit is required to construct, alter or repair a building, and that a contractor must be licensed or qualified before buying one. The county specifically warns homeowners not to pull a permit when a contractor asks them to, since that contractor may not be properly licensed or bonded. Towns such as Quinby and Timmonsville, and Darlington in neighboring Darlington County, may route permits through their own offices or the county, so confirm before work starts.

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

Most South Carolina home sales include a CL-100, the Official South Carolina Wood Infestation Report, which lenders typically require before closing. It's done by a licensed pest control company, covers termites, other wood-destroying insects and decay, and includes moisture readings in the crawl space.

South Carolina Regulation 27-1085 sets the moisture rules. The inspector takes representative wood moisture readings around the interior perimeter of the crawl space and in the accessible center, and the report lists those readings along with any decay, active decay fungi or excessive moisture. The regulation defines excessive moisture as wood readings that reach or exceed 20%, or standing water in the crawl space or around the foundation, and 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 normal correction, says poor drainage may call for a sump pump with a drain or trench system, and bars fungicide sprays on the substructure until the moisture problem is physically corrected.

Clemson University's Department of Pesticide Regulation oversees pest control licensing and lets you verify an applicator's license. If the report notes high moisture or damage, a crawl space company can find the cause.

Questions to ask a crawl space company

What LLR license or registration do you hold, and under what name?
Where is the moisture coming from: rain, groundwater or air?
Does this job need a permit, and will you pull it?
What liner, dehumidifier or supports are you proposing, and why?
How will inspectors and pest crews get in afterward?
What's warrantied, for how long, and what voids it?

Common questions

Does a crawl space contractor need a license in South Carolina?

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

What building code applies to crawl spaces in Florence, SC?

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 Florence County?

The City of Florence Building Department for addresses inside the city, and Florence County Building Inspections for the unincorporated county. Some towns may handle their own.

Florence crawl space guide (2026)