High Humidity
Crawlspace humidity above 60% is extremely common in the Upstate, especially from May through October. That excess moisture feeds mold, damages wood, and pushes damp air up into your living space through the stack effect.
If you own a home in Spartanburg or the Upstate, there's a good chance you have a crawlspace underneath it. Here's everything you need to know about what it is, why it matters, and when it needs attention.
If you've ever heard the word "crawlspace" and weren't entirely sure what it meant, you're in good company. A lot of homeowners in Spartanburg and across the Upstate live above a crawlspace every single day without really understanding what it is, what it does, or why it matters.
Simply put, a crawlspace is the shallow, enclosed area between the ground and the first floor of your home. It's typically somewhere between 18 inches and 4 feet tall — just enough room to crawl through on your hands and knees, which is exactly where the name comes from.
Your crawlspace isn't just empty space. It's where your home's plumbing, electrical wiring, HVAC ductwork, and foundation come together. Think of it as the mechanical hub of your house. When something needs to be repaired, replaced, or inspected underneath your home, the crawlspace is how contractors get to it.
In South Carolina, crawlspaces are one of the most common foundation types — far more common than basements. If you own a home in Spartanburg, Greenville, Greer, Boiling Springs, or anywhere in the Upstate, there's a strong chance your house sits on a crawlspace foundation. And while most homeowners never go down there, what's happening in that space directly affects the air you breathe, the energy you use, and the structural health of your home.
At JHS Crawlspace Specialist, we've been inside hundreds of crawlspaces across Spartanburg County and the surrounding Upstate communities. This guide covers everything you need to know as a homeowner — from why your home has a crawlspace, to the problems that can develop, to the modern solutions that keep your home dry, healthy, and protected.
The Upstate's terrain and climate make crawlspace foundations the practical choice for most builders.
If you've driven around Spartanburg, you've probably noticed that the landscape isn't flat. The Upstate has rolling hills, slopes, and a whole lot of red clay. That terrain is one of the biggest reasons crawlspace foundations are so common here.
Uneven ground. Pouring a flat concrete slab on a sloped lot is expensive and often impractical. A crawlspace foundation uses block or poured concrete walls that can be stepped to follow the natural grade of the land. This makes construction faster, cheaper, and better suited to the lots most Spartanburg homes are built on.
Elevation above water. South Carolina gets plenty of rain — especially during summer thunderstorms and the occasional tropical system that pushes up from the coast. A crawlspace raises the living space off the ground, keeping the home above surface water and reducing the risk of flood damage compared to a slab built at grade.
Access to systems. With plumbing, electrical, HVAC ducts, and drainage lines all running underneath the house, a crawlspace gives contractors access without having to tear up floors or dig through concrete. That access saves homeowners time and money on repairs throughout the life of the home.
Cost and speed. Full basements are rare in the Upstate because digging deep into South Carolina's clay soil is expensive. Crawlspace foundations offer a middle ground — elevated construction without the cost of excavating a full basement.
Whether your home was built in the 1960s or last year, if it's in Spartanburg, Greenville, Greer, Duncan, Inman, or the surrounding areas, a crawlspace foundation was likely the most sensible option the builder had. That's not a bad thing — as long as the crawlspace is properly maintained and protected from moisture.
If you've ever looked at the foundation of an older home in Spartanburg, you've probably noticed small rectangular openings near the ground — those are crawlspace vents. For decades, building codes required them. The theory was simple: let outside air flow through the crawlspace to ventilate it and keep moisture from building up.
In dry, mild climates, that approach can actually work. But in South Carolina's humid subtropical climate, crawlspace ventilation does the opposite of what it's supposed to do. When warm, humid Upstate air enters a cooler crawlspace through those vents, the moisture in the air condenses on every cool surface it touches — ductwork, floor joists, pipes, and the sub-floor above.
That's why building science has shifted. The U.S. Department of Energy and most crawlspace professionals now recommend sealing crawlspace vents in humid climates like ours. Modern vent sealing combined with a vapor barrier and dehumidifier keeps humidity controlled far better than open vents ever could.
If your Spartanburg home still has open crawlspace vents, it doesn't mean your builder did something wrong — it means the standards have changed. And upgrading to a sealed system is one of the most impactful improvements you can make for your home's air quality and structural health.
We'll inspect your crawlspace and show you exactly how those vents are affecting your home — free of charge.
South Carolina's climate is tough on crawlspaces. Here are the problems we see most often under homes across Spartanburg and the Upstate.
Crawlspace humidity above 60% is extremely common in the Upstate, especially from May through October. That excess moisture feeds mold, damages wood, and pushes damp air up into your living space through the stack effect.
Mold thrives when humidity stays above 55% and there's organic material nearby. Your crawlspace has plenty of both — wood joists, sub-floor, and old insulation. We find active mold in a significant number of the crawlspaces we inspect in Spartanburg.
Poor grading, clogged gutters, or missing downspout extensions can send rainwater straight toward your foundation. Once it collects in the crawlspace, it accelerates every other moisture problem and can attract mosquitoes and other pests.
When crawlspace humidity stays high, your floor joists and sub-floor absorb that moisture. Wood above 20% moisture content becomes vulnerable to decay fungi — the kind that causes soft spots, sagging, and structural damage over time.
Fiberglass batt insulation between floor joists absorbs moisture and sags, eventually falling out completely. Once it's waterlogged, it loses nearly all insulating value and becomes a breeding ground for mold.
That damp, earthy smell on your first floor? It's coming from your crawlspace. Mold, mildew, and decomposing organic material produce odors that travel upward through your floor system and into your living space — especially during humid summer months.
Your AC ducts carry cold air through a warm, humid crawlspace. That temperature difference causes condensation on the outside of the ductwork — dripping water onto insulation, barriers, or bare soil. It also makes your HVAC system less efficient and raises your energy bills.
Understanding where crawlspace moisture comes from is the first step toward fixing it.
Crawlspace moisture doesn't come from just one source. In Spartanburg and the Upstate, it's usually a combination of factors working together:
Ground evaporation. Exposed soil in a crawlspace constantly releases moisture into the air above it. Even soil that looks dry on the surface is releasing water vapor 24 hours a day. In South Carolina's warm climate, this evaporation is a major contributor to crawlspace humidity — and it's the primary reason vapor barriers exist.
Humid outside air. Open crawlspace vents pull in warm, moisture-laden air from outside. In the Upstate, outdoor humidity regularly exceeds 70–80% in summer. When that saturated air enters a cooler crawlspace, the moisture condenses on ductwork, pipes, joists, and other cool surfaces. This is one of the biggest moisture sources in vented crawlspaces.
Rainwater and drainage. Poor grading around the foundation, missing or disconnected downspouts, and inadequate drainage can channel surface water directly into the crawlspace. After heavy Upstate thunderstorms, we often find standing water in crawlspaces where drainage hasn't been addressed.
Concrete wall migration. Moisture can migrate through concrete block foundation walls over time, especially in areas with high water tables or poor exterior waterproofing. This isn't always obvious, but it contributes to overall crawlspace humidity levels.
Plumbing leaks. Slow leaks from plumbing lines, condensation on cold water pipes, and dripping connections can add moisture to the crawlspace for months or years before a homeowner notices.
In most Spartanburg homes, it's a combination of ground evaporation and outdoor humidity that drives the majority of crawlspace moisture problems. That's exactly what modern moisture control systems are designed to address.
A free inspection from JHS Crawlspace Specialist will identify the sources and give you a clear plan to fix them.
Encapsulation is the most effective way to control crawlspace moisture in South Carolina's climate.
If you've been researching crawlspace moisture solutions, you've probably come across the term "crawlspace encapsulation." It's the gold standard for crawlspace moisture control, and it's especially important for homes here in Spartanburg and the Upstate where humidity is a year-round challenge.
Crawlspace encapsulation is the process of completely sealing your crawlspace from outside moisture sources. It's not just laying plastic on the ground — it's a system of components that work together to create a dry, controlled environment underneath your home.
Here's what a proper crawlspace encapsulation includes:
The result is a crawlspace that's clean, dry, and conditioned — not a damp hole in the ground that's slowly damaging your home from below. Homeowners across Spartanburg who've had their crawlspaces encapsulated regularly tell us the musty smells disappear, their floors feel warmer in winter, their energy bills drop, and they just feel better about what's underneath their house.
Not every crawlspace needs a full encapsulation. Here are the solutions we use depending on what your crawlspace actually needs.
A heavy-duty liner over the ground and walls blocks soil moisture from evaporating into your crawlspace. This is the foundation of any moisture control system. Learn about vapor barrier installation.
The complete solution: sealed vapor barrier, sealed vents, dehumidifier, and airtight access door. Best for crawlspaces with persistent moisture, mold, or structural concerns. Learn about encapsulation.
Commercial-grade crawlspace dehumidifiers keep humidity below 55% year-round. They drain automatically, run quietly, and are designed for tight below-grade spaces. Learn about dehumidifier installation.
Permanently sealing crawlspace vents stops humid outside air from entering. This single step can make a dramatic difference in crawlspace humidity levels. Learn about vent sealing.
Targeted treatments for crawlspaces dealing with mold, mildew, and persistent odors. We address the source — not just the symptom. Learn about moisture and odor control.
Most homeowners in Spartanburg never look in their crawlspace. But the problems below that are easy to spot from inside your home.
Don't wait for the damage to get worse. A free crawlspace inspection will tell you exactly what's happening and what it'll take to fix it.
Every crawlspace is different. Here are the services that work together to keep your home dry and healthy.
Answers to the questions homeowners across Spartanburg and the Upstate ask us most about crawlspaces.
A crawlspace is the shallow, enclosed area between the ground and the first floor of your home. It's typically 18 inches to 4 feet tall — just enough room to crawl through. Crawlspaces give access to plumbing, electrical wiring, HVAC ductwork, and your home's foundation. In Spartanburg and across South Carolina, crawlspaces are one of the most common foundation types because the soil and terrain make them practical and affordable to build.
The Upstate SC landscape has rolling hills, red clay soil, and uneven terrain that makes pouring a flat concrete slab difficult and expensive. Crawlspace foundations adapt easily to sloped lots, keep the home elevated above surface water, and are faster and cheaper to build than full basements. That's why you'll find crawlspaces under the majority of older homes — and many newer ones — across Spartanburg, Greenville, Greer, Boiling Springs, and the surrounding communities.
Crawlspace moisture comes from several sources: ground evaporation from exposed soil, humid outside air entering through open vents, rainwater and poor drainage pushing water toward the foundation, condensation forming on cold HVAC ductwork, and moisture migrating through concrete block walls. In South Carolina's humid subtropical climate, these sources combine to create persistent high humidity that leads to mold, wood rot, and odors if left uncontrolled.
Crawlspace encapsulation is the process of sealing your crawlspace from outside moisture. It involves installing a heavy-duty vapor barrier over the ground and up the foundation walls, sealing all vents and access points, and adding a dehumidifier to control residual humidity. If your crawlspace has moisture issues, musty odors, mold, sagging insulation, or high humidity, encapsulation is the most effective long-term solution — especially in Spartanburg and the Upstate where humidity is a year-round concern.
Common signs include musty or damp smells on your first floor, visible mold or mildew under the house, sagging or falling insulation, soft or bouncy floors, condensation on windows or ductwork, higher-than-normal energy bills, and increased allergy symptoms indoors. If you notice any of these, it's worth having a professional inspect your crawlspace. JHS Crawlspace Specialist offers free inspections across Spartanburg and the Upstate — no pressure, just honest answers about what's going on under your home. Contact us to schedule yours.
Honest work, clear communication, and results homeowners actually notice.
No pressure, no scare tactics — just an honest look at what's going on under your home and what it'll take to fix it.