There is growth on the joists or subfloor, and a smell coming up into the house.
Mold in a crawl space is a moisture problem wearing a different name. It needs organic material to feed on, which a timber floor structure provides, and it needs sustained moisture, which a wet crawl space provides. Remove the moisture and it stops; remove the growth but leave the moisture and it returns, usually within a season.
That is why remediation here is done in a specific order. The affected material is removed or cleaned under containment so spores are not drawn up into the living space through floor penetrations, the air and surfaces are HEPA cleaned, and remaining surfaces are treated. Only then is it worth dealing with the barrier, drainage and ventilation that let the space get wet in the first place.
Crawl spaces matter more than their size suggests because of stack effect: air moves upward through a house, drawing crawl space air into the rooms above through gaps around pipes, ducts and floor penetrations. A substantial share of the air in the lowest story of a house can originate under it, which is why a crawl space problem is so often first noticed as a smell in a hallway.
You need this if
- Visible white, gray, green or black growth on joists or subfloor
- A persistent earthy or musty smell in rooms above
- Smell that intensifies when the heating or air conditioning runs
- Fuzzy or powdery deposits on the underside of the floor
- Dark water staining with a defined edge on framing
- Occupants reporting irritation that eases away from the house
What the work includes
- Survey of the affected area with the moisture source identified
- Containment and sealing of floor penetrations during works
- Removal and disposal of mold-affected porous material
- Cleaning of affected framing surfaces
- HEPA vacuuming and air filtration in the space
- Antimicrobial treatment of remaining surfaces
- A plan for the moisture correction the space needs
How we do it
Assess and identify the moisture
Survey the extent of growth and establish exactly what is keeping the space wet, because that determines whether remediation will hold.
Contain and protect
Set containment and seal floor penetrations so the work does not move spores into the living space, and protect access routes.
Remove affected material
Take out porous material that cannot be cleaned — insulation, barrier, debris — and clean affected framing surfaces.
HEPA clean and treat
HEPA vacuum and wipe surfaces, filter the air in the space, and apply an antimicrobial treatment to remaining surfaces.
Correct the cause
Address the moisture source through drying, barrier, drainage or ventilation work, so the space does not simply go back to how it was.
Common questions
Can I just spray bleach on it?
Spraying a surface biocide on damp timber treats the visible growth and leaves both the moisture and the material it is feeding on in place. It also adds water. Growth on porous material generally needs the material removed or properly cleaned, and the moisture source corrected, or it comes back.
Does mold under the floor affect the air in the house?
It can. Air tends to move upward through a house, pulling crawl space air into the rooms above through gaps around pipes, ducts and other floor penetrations. That is the usual reason a crawl space problem is first noticed as a smell upstairs rather than below.
Do you test the mold?
Identifying the species rarely changes what has to be done, because the response is driven by the extent of affected material and the moisture source. Where testing is needed for a property transaction, an insurance claim or a health question, that is best done by an independent hygienist rather than by whoever is doing the removal.
Will it come back after remediation?
Not if the moisture is corrected, and very likely if it is not. The durable part of this work is the barrier, drainage and humidity control, which is why we treat remediation and moisture correction as one job rather than two.
The rest of the sequence
Mold remediation is usually one stage of a larger job. These are the others.
Crawl Space Water Removal
Standing water pumped and extracted from under the house, then the saturated material taken out.
Crawl Space Structural Drying
Joists, girders and subfloor dried back to a measured target with air movers and dehumidification.
Crawl Space Vapor Barrier Installation
Sealed polyethylene over the soil and up the piers, so ground moisture stops entering the space.
Crawl Space Drainage and Sump Pump Installation
Interior drainage to collect water, a sump and pump to lift it, and a discharge that takes it away.
Crawl Space Wood and Subfloor Repair
Rotted joists, girders, rim joists and subfloor sections repaired or replaced once the space is dry.
Need mold remediation for your crawl space?
Call (888) 724-1354 and describe what you are seeing. We will tell you whether this is the right stage to start at.
Tell us what you are seeing under the house and we will tell you what it needs.