Find and stop the water, contain the area, put it under negative air, remove the material that cannot be cleaned, HEPA clean everything that stays, dry the assembly to a measured dry standard, then verify in writing. Seven stages, and the order is the whole point, because doing any of them out of sequence spreads what the sequence exists to contain.
The standard behind it is ANSI/IICRC S520, the mold remediation standard, which describes three conditions. Condition 1 is a normal fungal ecology. Condition 2 is settled spores and fragments. Condition 3 is actual growth. The job is to return the area to condition 1, and every stage below is a step toward that definition and not toward a clean looking wall.
Stage one, find and stop the water
Nothing else is durable until this is done. The EPA states it plainly: cleaning up the mold while leaving the water problem in place means the mold will most likely come back. In practice the source is a plumbing leak, a roof or flashing failure, ground water in a basement, or condensation from air that is simply too humid for the surfaces it is touching.
The humidity case is the one homeowners miss, because there is no leak to find. The EPA advises keeping indoor humidity below 60 percent relative humidity, ideally between 30 and 50 percent, and a finished basement here can sit above that all summer with no water event at all.
Stage two, containment
The work area is sealed off from the rest of the house with sheeting, and openings, vents and returns inside it are closed. Containment exists because removal disturbs growth. Cutting a piece of drywall out of an uncontained room takes a problem that was on one wall and distributes it through the house, and it is the single most common way a small job becomes a large one.
Ask to see the containment before the work starts. It is visible, it takes a minute to check, and its absence tells you what kind of job you have bought.
Stage three, negative air
An air scrubber with HEPA filtration is run inside the containment and exhausted so that the sealed area is at slightly lower pressure than the rooms around it. Air then moves into the containment, and anything disturbed inside stays inside. The same machines filter the air in the work area continuously while the work is going on.
Stage four, removal of what cannot be cleaned
Porous material with growth in it comes out. Drywall, insulation, carpet pad, ceiling tile and similar materials cannot be returned to condition 1 by cleaning their surface, because the growth is in the material rather than on it. Removal is cut back to sound material and the waste is bagged inside the containment before it is carried out.
Non porous and semi porous materials such as framing, masonry, metal and finished wood are usually cleaned rather than removed. That is the line that decides how much of a room leaves in bags, and a scope that removes far more than the growth justifies deserves a second quote.
Stage five, HEPA cleaning
Everything that stays is HEPA vacuumed and wiped, including surfaces above and beside the growth where settled spores and fragments have landed. This is the condition 2 part of the work, and it is why the cleaned area is larger than the area that had visible growth.
On the chemistry, the guidance is narrower than the folk advice. The EPA does not recommend a chemical or biocide that kills organisms, chlorine bleach for example, as a routine practice during mold cleanup, and it warns never to mix a bleach solution with cleaners containing ammonia because toxic fumes can be produced. Removal and cleaning do the work. A spray is not a substitute for either.
Stage six, drying to a measured standard
The assembly that got wet is dried and read with meters until it holds a dry standard, and never until it feels dry. Where a water loss caused the growth, this is the same drying work described on Water Damage Restoration, with readings logged at set monitoring points on each day the equipment is running.
The EPA advises drying water damaged areas and items within 24 to 48 hours to prevent mold growth. That window is why the drying and the remediation are one job and not two, and it is why nobody should be closing a wall up on a reading nobody took.
Stage seven, verification in writing
Post remediation verification is the written check that the area has been returned to condition 1. It should record the visual result, the moisture readings, and any sampling that was agreed at the start, and it should be a document you can hand to somebody else, including a buyer or a carrier.
Ask at the quote stage what the verification will consist of and who performs it. Getting that answer before the work is the cheapest quality control available on this kind of job.
How long it takes and what it depends on
- The area of growth and how many rooms or assemblies it sits in.
- Whether the material is porous, which decides removal against cleaning.
- Whether the water source is fixed before work starts, or has to be sequenced with a plumber or a roofer.
- How wet the assembly is. Drying is measured, so it ends when the readings at the fixed monitoring points hold at a dry standard, and hardwood, plaster and concrete take longer than carpet because they release water slowly.
- Access, containment and how much of the house has to keep working while the job runs.
Nobody can give you a duration on the phone without those five answers, and a duration given without them is a guess.
The New Jersey line about licensing
New Jersey has no state mold remediation license. The Department of Health publishes guidance and does not license remediators, so no company here is state licensed for mold. What a company can hold is IICRC certification, and home improvement work in the state requires registration with the Division of Consumer Affairs, whose 13VH number must appear in advertising and on estimates. DHL is IICRC certified, licensed and insured.
The full method, including containment and verification, is on Mold Remediation. What an inspection covers before any of this starts is in What happens during a mold inspection in New Jersey.
This article is about Mold Removal.