Wood rot and moisture damage
Years of damp crawl space air can rot the wood that holds up your floors. Here's how it's found and fixed, and how it ties into South Carolina's wood infestation report.
Wood under a house can stay sound for a century if it stays dry. When it doesn't, decay fungi move in. The damage usually starts where moisture concentrates: sill plates on top of the foundation, rim joists behind leaky gutters, and joists and subfloor under bathrooms, kitchens and water heaters.
What moisture levels matter?
South Carolina's regulation on wood-destroying organisms gives clear numbers. It treats wood moisture readings of 20% or more, or standing water in the crawl space or around the foundation, as an excessive moisture condition. It says wood-decay fungi become active, and decay damage occurs, at 28% and above. The same rule says fungicide sprays shouldn't be applied until the moisture problem is physically corrected.
Where does the CL-100 come in?
The Official South Carolina Wood Infestation Report, widely called the CL-100, must be issued by a licensed pest control business. The inspection covers accessible crawl spaces, and the report has to list representative moisture readings around the inside perimeter of the crawl space and disclose damage, decay and excessive moisture it finds. When a report used for a sale or a mortgage turns up rot or high readings, a crawl space company is often the one called to make the structural and moisture repairs.
How is rot repaired?
- Probing and mapping the extent of soft wood
- Temporary support while damaged pieces come out
- Replacing or sistering sill plates, rim joists and floor joists
- Patching or replacing subfloor where it has softened
- Fixing the source: leaks, gutters, grading, a ground liner or encapsulation
Warning signs
- Wood that a screwdriver sinks into easily
- Dark staining, fuzzy growth or cracked, cube-shaped breaks in wood
- Soft floor near a tub, toilet or the dishwasher
- Moisture or decay noted on a wood infestation report
We don't offer mold testing or mold remediation, and we don't make health claims. If there's heavy growth, ask the crawl space company about a specialist.
Pricing is set by the crawl space company after someone has been under the house, measured it and seen what's wrong. We don't quote prices, and a figure given over the phone before an inspection is a guess at best.
Where we connect you with help
Common questions
Does a CL-100 cover more than termites?
Yes. South Carolina's report must disclose damage, decay and excessive moisture found in accessible areas below the first floor, along with crawl space moisture readings.
Can rotted joists be fixed without tearing up the floor?
Usually. Most sill, joist and beam repairs are done from the crawl space by sistering or replacing wood, though badly rotted subfloor may need work from above.
Related services
- Crawl space encapsulation
- Crawl space dehumidifiers
- Sagging floor support
- Crawl space drainage and sump pumps
More background: Spartanburg crawl space guide.
Musty smell, sweating ducts or a floor that's started to dip?
Call the number above and a local crawl space company will help you figure out what's happening under the house.