Mold on the joists isn't a cosmetic problem — it's a moisture problem. We clean the mold with antimicrobial treatment and HEPA vacuum, then fix the humidity that caused it so it doesn't come back in six months.
A licensed local crew — usually out in 24 to 72 hours. Written scope, fixed price, no pressure.
A month ago I crawled under a 1977 split-level off John St, a couple of blocks toward Trade St from the Downtown Matthews grid. The homeowner had smelled a musty odor in the master bedroom closet for about six months and had finally called after her doctor mentioned a possible mold sensitivity in her allergy panel. Under the house: 20 inches of clearance, foil fiberglass in shreds, and visible microbial growth on the underside of the subfloor across a 12-foot span directly under the master bedroom. The growth was black and white patches on the pine subfloor and had propagated up into the joist bays on both sides. Moisture reading at the joist bearing was 32 percent — well above the 20 percent threshold where wood-destroying fungi become active.
The source was a slow leak from the master bathroom shower drain that had been dripping onto the girder for years, plus the general 82 percent RH crawl environment providing the humidity to keep fungal growth active. Mold remediation is not just cleaning the visible growth — you have to address the moisture source, remove or treat the affected material, apply an EPA-registered antimicrobial to arrest active growth, and then re-establish an envelope that will not re-support fungal activity going forward. On this Matthews split-level the scope was: fix the shower drain leak (separate plumbing scope), remove and dispose of all affected fiberglass insulation, sand and treat the exposed subfloor and joist areas with a borate-based antimicrobial, encapsulate the crawl with 20-mil liner and mechanical wall termination, add a Santa Fe Compact 70 dehumidifier, and re-insulate the rim joist with open-cell foam. Five-day job with a two-person crew.
Mold under Matthews houses is not a rare condition. The combination of 1970s-80s split-level tract construction with fiberglass batts in joist bays above leaky ductwork, low clearance that traps humidity, and Piedmont summer dew points in the low 70s creates an environment where microbial growth on framing is almost inevitable if the moisture is not managed. On the pre-1970s Trade St stock with brick pier crawls the same story plays out at a slower pace but eventually gets there. On the 2000s subdivisions with builder partial encapsulations the sealed vents plus no dehumidifier means moisture that gets in cannot get out, and growth appears within 5 to 10 years.
Free on-site inspection with moisture readings and visual growth documentation anywhere in Matthews and out to Mint Hill, Stallings, Weddington, and Indian Trail. Fixed written scope. If your issue is beyond crawl remediation and needs an IEP (indoor environmental professional) or a certified industrial hygienist, I will tell you that and refer you to the right specialist.
The process on a Matthews mold remediation is different from a straight encapsulation because you are dealing with active biological contamination, and the sequence matters more than on a moisture-only job.
Source identification. First thing under the house is finding the moisture source that is feeding the growth. Growth without a moisture source is not a real problem — mold spores are present in every crawl and only become active when moisture is available. On Matthews split-levels the source is usually one of: ductwork condensate leaking onto fiberglass, a plumbing drain leaking above the crawl (bathroom or kitchen), a foundation vent that has been letting in exterior moisture at high rates, a downspout discharging near the foundation, or a broken sump / no sump on a crawl that gets water intrusion. On the pre-1970s Trade St houses the source is often a combination of high perimeter moisture from unsealed brick piers plus the general 80+ percent RH environment. Identifying and stopping the source is the prerequisite for remediation — you cannot remediate mold in an environment that will re-support it within a year.
Containment and PPE. On any Matthews job where visible growth exceeds about 10 square feet, we set up containment at the crawl access — 6-mil poly sheeting sealing the hatch with a zippered entry, HEPA-filtered negative air machine running during work hours to keep spores from migrating into the living space above. Crew PPE is Tyvek suits, half-face respirators with P100 cartridges (or full-face if growth is heavy), nitrile gloves, disposable boot covers. On smaller isolated growth spots (under 10 square feet) containment is less formal but PPE is the same.
Material removal. All affected fiberglass insulation gets bagged and disposed of — it cannot be salvaged once it has supported mold growth. Any subfloor sections that are structurally compromised (spongy, crumbling) get cut out and replaced (that overlaps with the crawlspace repair scope). Subfloor that is stained but structurally sound gets treated in place. Any rotted framing (rim joist, sill plate, joists) gets addressed structurally before antimicrobial treatment.
Antimicrobial treatment. Exposed wood surfaces (subfloor underside, joists, girders, sill plate, rim joist) get an EPA-registered antimicrobial applied at label rates. My default is Concrobium Mold Control for surface treatment and Bora-Care for penetrating treatment of any wood that will stay in place. Both products are widely used in the remediation industry, both are effective against the common Aspergillus / Penicillium / Cladosporium species we see in Charlotte crawls, and both are approved for occupied space (no re-occupancy delay required after treatment). Application is by pump sprayer with attention to full surface coverage.
Post-treatment verification. After treatment we do a visual re-inspection and take moisture readings across the treated area. If the homeowner wants third-party air quality testing or surface sampling for verification, I refer to an independent industrial hygienist — I do not do the testing myself because the party doing remediation should not also be verifying the work. That is a small additional cost but it is worth it for peace of mind and for documentation if the mold issue was tied to a health concern or an insurance claim.
Envelope reconstruction. After remediation is complete we install the full encapsulation scope — 20-mil liner, sealed vents, individually wrapped piers, mechanical wall termination, dehumidifier — to create an envelope that will not re-support fungal growth. Open-cell foam on the rim joist. Rockwool ComfortBatt R-15 in any joist bays that were re-insulated. Dehumidifier setpoint at 55 percent RH.
Permits. Mold remediation itself is not a permitted trade in Mecklenburg or Union County. Any structural repair or dehumidifier electrical work bundled into the scope does have permit requirements — we handle those.
Antimicrobial products I spec on Matthews jobs are Concrobium Mold Control for surface application and Bora-Care for penetrating wood treatment. Both are EPA-registered, both are approved for occupied space, both are effective against the common Charlotte crawl fungi (Aspergillus niger, Penicillium chrysogenum, Cladosporium sphaerospermum, and occasionally Stachybotrys chartarum in the wettest crawls). Application is by pump sprayer at label rates with full surface coverage.
Containment materials are 6-mil poly sheeting for the temporary crawl-access barrier and Zipwall or Zippers seal systems for the entry point. Negative air machine is a HEPA-filtered unit (Abatement Technologies HEPA-Aire H1000 or equivalent) running during work hours to keep spore counts down and prevent migration into living space above.
PPE is standard mold remediation gear: Tyvek 400 or 500 series disposable coveralls, North 7700 series half-face respirators with 3M P100 particulate cartridges, or 6900 series full-face respirators when growth is heavy. Nitrile gloves double-layered for tear resistance. Disposable boot covers over work boots for entry and exit.
Debris disposal is standard construction bags (contractor grade, 3-mil thick) double-bagged and hauled off-site to the Mecklenburg County landfill or the Speedway Blvd transfer station. Fiberglass insulation carrying visible growth is technically construction debris, not hazardous waste, but we treat it as if it were and dispose accordingly.
Post-treatment moisture verification uses a Delmhorst BD-2100 moisture meter (pin-type for penetrating readings) plus a General Tools infrared moisture meter for non-destructive spot checks. Target reading is under 15 percent for framing and under 12 percent for subfloor material. Higher readings indicate the moisture source has not been fully addressed and re-treatment is likely.
Third-party air quality verification (when the homeowner requests it) is done by an independent industrial hygienist with samples analyzed by an AIHA-accredited lab. Typical sampling is two indoor air samples plus one outdoor control, analyzed for total spore counts and genus-level identification. Results usually available in 3 to 5 business days.
Yes — Matthews is a regular mold remediation route. Free on-site inspection anywhere in Matthews, fixed written quote before we touch anything.
Matthews mold remediation is heavily driven by the ductwork condensate + fiberglass batt combination on 1970s-80s split-level tract construction where four decades of duct joint leaks have kept the insulation and adjacent subfloor at moisture levels that support active fungal growth, and by the builder partial encapsulations on the 2000s subdivisions that sealed vents without adding dehumidification and turned themselves into moisture traps.
28104, 28105. All Mecklenburg County addresses covered.
Mold on subfloor and joists usually shows as discrete patches of black, white, green, or grey growth with a fuzzy or velvety surface texture, often propagating in visible patterns along wood grain or fiberglass edges. Dirt is uniformly deposited, does not have a distinct edge, and does not have a texture beyond fine particulate. When in doubt, moisture content of the wood tells the story — wood at 15 percent moisture content or below does not support mold growth even if some spores are present. Wood at 20 percent or above with visible discoloration is almost always active or recently active growth. On the free inspection I take moisture readings across the affected area and can usually tell you within a couple of minutes whether you are looking at active growth or old growth that has dried out.
Depends on the situation. For most Matthews split-level jobs where the mold is limited to the crawlspace and not associated with a health complaint, the remediation scope plus post-treatment moisture verification is enough — the visible growth is gone, the moisture source is fixed, the antimicrobial has treated the wood, and the new envelope will not re-support growth. If someone in the household has a documented mold sensitivity or immune issue, or if the issue is tied to an insurance claim, third-party air quality testing before and after remediation is worth the additional cost for documentation. I refer to independent industrial hygienists in the Charlotte metro for that work — the party doing remediation should not also be verifying it.
Depends on your policy and the source of the moisture. Most standard homeowners policies exclude mold caused by chronic moisture (long-term ductwork condensate, high RH from unsealed crawls) but will cover mold caused by a sudden discrete event (a burst pipe, a storm-related roof leak). Some carriers in North Carolina have quietly added mold exclusions to vented-crawlspace homes since about 2022 — you may find at claim time that your carrier will not cover crawl mold regardless of source. Worth calling your agent to understand your specific policy before you file a claim. On the estimate I write scopes that can be broken out by line item so if part of the scope is covered and part is not, we can bill separately.
Because we address the moisture source and rebuild the crawl envelope to hold humidity under 55 percent RH — mold spores are always present in the environment but they only become active growth when moisture is available. A properly encapsulated Matthews crawl with a functioning dehumidifier holds moisture content of framing under 15 percent year-round, which is below the threshold where wood-destroying fungi can establish. If the dehumidifier fails or the envelope is compromised (foot traffic tears the liner, HVAC service disturbs the wall termination), moisture can re-enter and growth can re-establish. Annual crawl inspection is cheap insurance — I offer a service agreement that includes it.
Free on-site Matthews inspection. Fixed written quote. Call (980) 227-1769 or book below.