What people mean by "black mold"
The term almost always refers to Stachybotrys chartarum, the species that drove the toxic-mold coverage of the early 2000s. It is real, it does produce mycotoxins, and it does show up in Clark County homes — but it is genuinely uncommon compared to the things that look just like it. Stachybotrys needs material that has been wet more or less continuously for a week or more, and it strongly prefers cellulose: paper-faced drywall, cardboard, wallpaper backing, and old wood. It is slimy and greenish-black when it is actively growing, and sooty when it dries.
What is far more common on a dark patch in a Vancouver home is Cladosporium, which is olive to nearly black and grows happily on window sills, bathroom surfaces, and the cool side of exterior walls. Or Aspergillus in one of its darker forms. Or, on the underside of attic sheathing, the grey-black surface staining that is a normal PNW condensation signature. You cannot tell them apart by looking, and neither can a contractor — only a lab can. Which leads to the practical point.
The remediation protocol is the same regardless of species. Contain the area, remove porous material that has growth on it, HEPA filter the air, clean non-porous surfaces, dry everything out, and fix the water. Identifying the species can matter for an insurance claim or a health conversation with a doctor, but it does not change what a competent contractor does on site. Anyone using a species name to justify a dramatically higher price is selling fear.
Why it shows up here
Stachybotrys needs sustained saturation, not just humidity, so in Vancouver it tends to follow a specific, findable event: a supply line that dripped inside a wall for months, a toilet flange that leaked into the subfloor, a roof or flashing failure that soaked the sheathing and the insulation below it during a long wet stretch, or a crawl space where standing water sat against the underside of the floor. The eight-month wet season matters because it removes the natural drying window — a small leak that would dry out between rains in a drier climate simply never dries here.
That is also why the first question a good pro asks is not "what color is it" but "how long has this been wet." The answer tells them what they are likely to find behind the surface.
Dark growth around a tub surround in an unvented bathroom
After removal, ventilation correction, and rebuild
What safe removal looks like
The single most important principle: do not disturb it before it is contained. Dry Stachybotrys and dried Cladosporium both release enormous numbers of spores when scrubbed, scraped, or hit with a shop vac. A homeowner who attacks a dark patch with bleach and a brush on a Saturday can turn a one-room problem into a whole-house problem in twenty minutes.
- Containment first. Plastic barriers, zippered entry, negative air pressure through a HEPA-filtered air scrubber that exhausts outside. HVAC in the affected zone shut down and returns sealed.
- PPE that matches the job. At minimum an N95; for larger or heavily contaminated areas, a half- or full-face respirator with P100 cartridges, disposable coveralls, and gloves.
- Porous material comes out. Drywall, insulation, carpet and pad, ceiling tile, and affected trim are cut out past the visible edge and double-bagged inside the containment before they leave.
- Non-porous surfaces get cleaned, not just sprayed. Framing, concrete, metal, and tile are HEPA vacuumed and physically wiped. Removal is mechanical. Biocides are a supplement, never the method.
- Dry to a measured target. Air movers and dehumidifiers until moisture content readings come down, verified with a meter.
- Verify. On a job of any size, clearance air sampling compared against an outdoor control confirms the space is genuinely back to normal.
About bleach
Bleach is the most common DIY mistake in the Pacific Northwest and it fails for a specific reason. On porous materials like drywall and framing lumber, the chlorine stays on the surface while the water carrier soaks into the material — feeding the growth you were trying to kill and leaving the roots, or hyphae, intact below. The patch turns pale, you assume it worked, and it returns in a few weeks looking worse. On hard, non-porous surfaces bleach is fine for a small, superficial spot. On anything porous, the material either gets removed or it stays contaminated. Never mix bleach with ammonia or with acidic cleaners, which produces genuinely dangerous gas.
Health, honestly
The evidence on indoor mold and health is solid on some points and thin on others, and it is worth being straight about the difference. What is well established: damp indoor environments are associated with increased respiratory symptoms, worsened asthma, and allergic reactions, and people with asthma, allergies, immune suppression, or chronic lung disease are meaningfully more affected. What remains contested: the sweeping "toxic mold syndrome" claims that were common two decades ago, which the broader medical literature has not supported at the level those claims implied. Either way, a persistently damp house is a health issue worth fixing, and if anyone in your home has symptoms that track with being indoors, that is a conversation for a physician alongside the remediation. Our mold and health article goes into more depth, and types of household mold covers what you are actually likely to be looking at.