Start here: you cannot identify mold by looking at it
This is the most useful thing in this article. Colour, texture, and location will not tell you the species — several unrelated organisms look essentially identical on a damp wall, and the same organism looks different depending on what it is growing on and how wet it is. Only a laboratory, working from a tape lift, swab, or air sample, can identify what you have. Any contractor who tells you from the doorway that it is definitely black mold is either guessing or selling.
And here is why it matters less than you would expect: the remediation is the same regardless. Contain the area, remove porous material with growth on it, HEPA filter the air, clean non-porous surfaces mechanically, dry to a measured target, and fix the water. Identification is genuinely useful for documentation — an insurance claim, a landlord dispute, a conversation with a doctor — and it does not change what a competent crew does on site.
Cladosporium
Probably the most common indoor mold in the Pacific Northwest, and the one most Vancouver homeowners are actually looking at when they say "black mold." It ranges from olive-green to brown to nearly black and grows in a velvety or powdery layer. It tolerates cool conditions better than most, which is exactly why it thrives here: it colonises window sills and frames where condensation collects, bathroom surfaces, the cool interior face of exterior walls, painted surfaces, fabrics, and the underside of attic sheathing. It is also abundant outdoors year-round in this climate, which is why an air sample without an outdoor control sample tells you nothing.
Aspergillus
A very large genus with many species, appearing in shades of green, yellow, brown, grey, and black. Common in house dust, on damp building materials, in HVAC systems, and in crawl spaces. Some species are significant allergens, and a few are genuinely dangerous to people with severely compromised immune systems, which is why remediation guidance treats immunocompromised occupants as a special case.
Penicillium
Blue-green, often with a white edge, typically velvety. Grows readily on water-damaged materials — wallpaper, carpet, insulation, drywall — and on food. It spreads quickly once established and is a common allergen. In Clark County it turns up frequently on materials that got wet in a leak and were never properly dried, which makes it a useful indicator that something was wet for a while.
Stachybotrys chartarum
The famous one. Greenish-black and slimy when actively growing, sooty when dried. It is much less common than its reputation suggests because its requirements are specific: it needs cellulose-rich material — paper-faced drywall, cardboard, wallpaper backing, older wood — that has been continuously wet for roughly a week or more. It does not grow on merely humid surfaces. In Vancouver homes it typically follows a findable event: a leak inside a wall, a failed toilet flange soaking a subfloor, or standing water in a crawl space. Our black mold removal page covers the handling.
Alternaria
Dark brown to black, with a woolly or downy texture. Common in damp bathrooms and around sinks and showers, and extremely abundant outdoors, particularly in late summer and autumn. It is a well-known allergen and is frequently implicated in allergic rhinitis and asthma.
Aureobasidium
Starts pink or cream and darkens to brown or black as it matures. It is the organism most often responsible for the dark growth on bathroom caulk and grout, on window frames and painted wood trim, and behind wallpaper. If you have black stuff on your shower caulk in a Vancouver bathroom, this is a leading candidate.
Chaetomium
Cotton-like when young, darkening to grey or black. It shows up on water-damaged drywall and wood, often alongside Stachybotrys and in the same conditions — sustained saturation. It is associated with a distinctly musty odour and is a reasonable sign that a leak ran for a long time.
Serpula lacrymans and the rot fungi
Worth naming separately because they are a different category of problem. Wood-destroying fungi consume the structural fibre of lumber rather than merely growing on its surface, and in a damp Pacific Northwest crawl space they are a genuine risk. The distinction matters practically: mold is an air quality and health issue, while rot is a structural one. A floor joist that is soft to a screwdriver probe has rot, and no amount of antimicrobial treatment addresses that — it needs a carpenter. Have any crawl space assessment tell you explicitly which you are dealing with, because it is often both.
What to do with all this
If you can see growth and you know where the water came from, you do not need a species name to move forward — you need the material removed and the water stopped. If you cannot find the source, if a home sale or a rental dispute is involved, or if someone in the house has health symptoms, lab identification and documentation are worth paying for. Either way, do not disturb dry growth before it is contained. Our inspection and testing page explains when the lab work earns its cost, and you can reach us at {phone} to get matched with a local pro.