Crawl Space Mold in Georgia Homes

Why do so many Georgia crawl spaces get moldy?

Much of metro Atlanta's older housing stock sits over a vented crawl space, and the climate works against that design for months at a time. Summers here are long, hot and humid. When outside air full of moisture drifts through foundation vents and meets wood, ductwork or pipes that are cooler than the air, the moisture condenses. Wood that stays damp for weeks becomes food for mold.

The soil adds to the problem. Georgia's red clay drains slowly, so after a heavy thunderstorm the ground under a house can stay wet long after the yard looks dry. Bare dirt in a crawl space gives off water vapor all day. Add a leaking supply line, a sweating air conditioning duct or a downspout that dumps water against the foundation, and the space under the floor can hold more moisture than the living area above it.

UGA Extension's home checklist puts it simply: mold needs a comfortable environment, a food source such as wood or paper, and moisture. A crawl space under a Georgia house often supplies all three.

What are the signs of mold under the floor?

• A musty or earthy smell in rooms over the crawl space, often strongest when the AC first kicks on.
• White, gray, green or black growth on floor joists, beams or the underside of the subfloor.
• Insulation between joists that sags, drips or has fallen to the ground.
• Condensation on ductwork or water lines, or puddles on the vapor barrier.
• Soft spots, cupping or squeaks in wood floors above.

Color tells you nothing about how risky a particular mold is. What matters is how much growth there is, what it is growing on and why the area is wet. If you notice several of these signs inside the house too, our checklist of household mold warning signs covers the rooms above.

Does it matter that the crawl space is outside the living area?

It matters less than many people assume. Air moves up from a crawl space into the house through gaps around pipes, wires and duct boots. In many Atlanta homes the HVAC air handler and supply ducts run through the crawl space as well. EPA advises not running an HVAC system you know or suspect is contaminated with mold, because it can spread spores through the building. If the growth reaches the duct system, the job grows, and a look at mold in Atlanta duct systems explains what changes.

On health, EPA notes that mold exposure can irritate the eyes, skin, nose, throat and lungs, and that people with asthma or weakened immune systems should stay away from moldy areas. Anyone with health concerns should talk with a health professional.

Can I clean crawl space mold myself?

EPA's general rule is that a homeowner can usually handle a moldy area smaller than about 10 square feet, roughly a 3 by 3 foot patch. Crawl spaces rarely stay that small. By the time someone notices a smell, growth is often spread across many joists, the space is cramped and dark, and the person doing the work is lying in the dirt next to the material being scrubbed. For anything larger than that small patch, or where there has been a lot of water damage, EPA points to its guidance for schools and commercial buildings, which calls for containment and protective gear.

Also keep in mind what EPA says about porous materials: moldy insulation is usually thrown away, not cleaned. And painting or spraying a coating over growth without removing it and fixing the moisture is not a fix.

What does a real crawl space fix include?

A sound plan has two halves. The first half removes what is already there. The second half keeps it from returning.

1. Find the water source. Plumbing leaks, sweating ducts, poor grading and gutter discharge are the usual suspects. EPA is direct about it: the key to mold control is moisture control, and the mold comes back if the water problem stays.
2. Remove damaged materials. Wet or moldy insulation, debris and torn plastic come out.
3. Clean the wood. Joists and subfloor are cleaned of surface growth and dried. Badly decayed wood may need repair or sistering.
4. Cover the ground. UGA Extension's checklist says that, at a minimum, a 6 to 8 mil plastic vapor barrier should cover the soil.
5. Control humidity. EPA recommends keeping indoor humidity below 60 percent, ideally 30 to 50 percent. UGA's checklist suggests considering a dehumidifier if a basement or crawl space reads over 50 percent.
6. Fix the outside. UGA advises keeping gutters and downspouts clear and pointed away from the house, with soil sloping about 6 inches over 6 to 10 feet.

Some homes go further with full encapsulation, which seals the walls and vents along with the floor. It is a bigger decision with bigger costs, and whether it fits depends on the house. Ask the company to explain why their plan suits your foundation, drainage and HVAC layout rather than accepting a one-size package.

The Atlanta crawl space mold page walks through how local companies usually stage this work.

What does crawl space mold remediation cost in Atlanta?

Prices depend on the square footage affected, how much clearance there is to work, how much material has to be thrown out and what moisture fixes are added. Use these figures as a starting point, not a quote.

A full breakdown by room and job type is in our Atlanta mold remediation cost guide. Ask every company to separate removal, moisture work and any structural repair on the written quote so you can compare like with like.

Do I need a test before crawl space work?

Usually not if the growth is plainly visible. EPA says that in most cases, when visible mold is present, sampling is unnecessary, and that no federal limits exist for mold or spores. Where testing earns its fee is after the job: EPA notes surface sampling can help show whether an area has been adequately cleaned. For more on when lab results add value, read whether mold testing is worth paying for, or see how clearance testing after cleanup is handled in Atlanta.

What about crawl spaces that flooded?

Creek flooding is a real risk in parts of the metro. In the September 2009 floods, the National Weather Service recorded Sweetwater Creek, Noses Creek and Powder Springs Creek gauges at Powder Springs all well above flood stage, and USGS reported that flood magnitudes on Powder Springs Creek greatly exceeded the estimated 500-year flood. If your home sits near one of these creeks in Powder Springs, or near Sweetwater Creek, see the page on Austell crawl spaces.

EPA's disaster guide says that if a flooded home could not be dried within 24 to 48 hours, you should assume mold is growing. A crawl space that held standing water deserves an inspection even if nothing is visible yet.

Who should do the work, and what should I check?

Georgia has no state license or certification for mold remediation, and Georgia DPH says mold inspection, testing and remediation have no enforceable state or federal standards. That puts the checking on you. Crawl space jobs can include replacing joists, sill plates or subfloor, which is construction work. Georgia law defines a residential contractor by work over $2,500, so ask whether the company holds a Georgia residential or general contractor license and check it on the Secretary of State's GOALS Verify Now lookup. Confirm the current threshold with the state licensing board before relying on it.

Structural repairs may also need a local permit. Johns Creek, for example, requires permits for interior alterations that involve framing or drywall, so ask whether your city or county requires one for your scope. Our step-by-step guide to vetting a Georgia mold company covers the questions to ask, and if the damage traces back to a burst pipe or storm, read how Georgia homeowners policies treat mold before work starts.

Homes on hillside lots around the metro often pair a crawl space with a partial basement. If yours does, the Marietta crawl space mold page and our Atlanta basement mold guide cover both halves of the foundation.