Mold Testing for Apartment Buildings and Multifamily

Multifamily mold testing is documentation work. You are not buying a diagnosis for its own sake. You are buying a dated third-party record that establishes what was present in a unit on a specific day, who was told, and what condition the building was in, because that record is what ends a habitability complaint, supports or defeats a claim, and lets you turn a unit without carrying an unresolved question into the next tenancy.

We test only. No remediation, no bids, no referral fees. A report from a company that then quotes the repair is a report a tenant advocate can attack on one sentence, and you are the party who has to defend it.

Multi-unit work is quoted, typically $0.10 to $0.20 per square foot plus per-sample, with volume rates for portfolio scope and net 30 for established accounts. Single-unit assessments in a multifamily property start in the $650 to $950 range for anything under 5,000 square feet, and cluster pricing drops that materially when we do several units in one mobilization.

The three multifamily jobs

Turnover testing. A unit had a water event, a crew dried it, and you need to know whether it is rentable before a new lease starts. Drying removes water. It does not undo growth that established while material was wet, and it does not tell you whether wet material behind a finish was ever reached. Turnover testing is the cheapest insurance in this business, because a documented clean unit at move-in is far more defensible eleven months later than any argument you can make after a dispute has started.

The complaint that will not close. A tenant reports mold. Maintenance looks. The tenant does not accept the answer. Now there are emails. The exposure here is not the mold, it is the absence of a record produced by someone with no stake. Instrument readings, photographs keyed to locations, laboratory data with chain of custody, and an outdoor control from the same property on the same day. It is checkable by a person who was not there, which is precisely why it settles things.

Cause attribution. Tenant says the building leaks. Owner says the tenant never runs the bath fan and dries laundry indoors. Both are common and both are sometimes true. These read differently on instruments. Occupant-driven condensation concentrates on the coldest surfaces, tracks interior relative humidity, peaks in winter, and leaves the wall cavity dry behind the surface growth. Envelope or supply-line intrusion wets the cavity and the framing, shows a thermal signature that follows the water path rather than the thermal bridge, and does not resolve when the humidity drops. That is a technical answer instead of a standoff.

RCW 59.18.060 and what it actually requires

Washington's Residential Landlord-Tenant Act requires a landlord to keep the premises fit for habitation, to maintain the structure and the systems supplied, and to provide tenants with written information about the health hazards associated with indoor mold. RCW 59.18.070 sets response windows once a tenant gives written notice: 24 hours for a hazardous condition or loss of heat or water, 72 hours for a major plumbing fixture or appliance supplied by the landlord, and 10 days for other defects materially affecting health and safety. Mold complaints almost always ride on top of a water condition that lands in one of those windows.

Two things the statute does not do. It does not require testing, and it sets no numeric threshold. There is no legal limit for airborne mold in Washington, in Idaho, or in federal law, so nothing passes or fails a statutory standard. Testing in this context is dispute-driven and evidentiary. You order it because you need a record, not because a rule compels it.

Idaho has no analogous mold notification provision. The habitability framework there is thinner, which in practice means disputes turn even more on documentation quality and lease language.

Two practical consequences. First, respond to written notice inside the statutory window regardless of whether you have test results yet, because the window runs on the notice, not on the investigation. Second, an inspection report that overclaims can create obligations you did not have. We keep health language accurate for that reason. CDC has never established a causal link between Stachybotrys and serious illness, and says no test proves an association between a specific mold and particular health symptoms. Documented effects are allergic reaction, asthma triggering and upper respiratory irritation in sensitive people, plus serious infection risk in the severely immunocompromised. We do not diagnose anyone.

Scheduling across occupied units

This is where multifamily work succeeds or fails operationally.

Give us the unit list, not one address at a time. Several units at one property, or several properties inside a tight radius, get built into a single day. One mobilization instead of six is where portfolio pricing comes from, and it is the difference between a $950 unit and a materially lower per-unit rate.

Notice is yours, coordination is ours. Tell us your notice requirements and who serves them. We will hold a window and work inside it. If entry is likely to be refused, say so in advance so we hold the slot rather than lose the day.

Tell us the conditions. Pets, hoarding, a tenant who has retained counsel, a unit with active water. Each changes how we staff and sequence the visit. We would rather know than discover.

On-site conduct in an occupied unit. We explain what we are doing, answer factual questions about method, and decline to offer any opinion about fault, rent, or who should pay. We do not sell the occupant anything, because we have nothing to sell.

Common areas matter. In a stacked building, the source is frequently outside the complaining unit: a crawlspace or below-grade parking level, a shared plumbing chase, a laundry room exhaust that terminates in the attic, or a roof drain. Sampling a single unit without looking at the stack often produces a clean result and an unsolved problem.

What each unit assessment includes

• Air sampling with a calibrated pump drawing a measured volume through an Air-O-Cell or Allergenco-D spore trap cassette, analyzed by an accredited laboratory using direct microscopic examination
• An outdoor control at every property, every visit. Outdoor air always contains mold spores. An indoor number with no same-day outdoor baseline supports no conclusion. This is the most common defect in reports we are asked to review, and it is fatal to them
• Surface sampling by swab or tape lift to confirm visible growth is fungal rather than staining or soap scum residue
• Moisture mapping with pin and pinless meters, including the shared wall and the floor and ceiling assemblies where a stack is implicated
• Thermal imaging for temperature differentials behind intact finishes
• Borescope inspection into wall cavities and chases where a visual answer is needed without demolition
• Psychrometrics: temperature, relative humidity and dew point in the unit and outdoors, which is the reading that separates occupant-driven condensation from intrusion
• Written report per unit, with photographs keyed to locations, raw laboratory data, indoor to outdoor comparison and chain of custody

Post-remediation verification includes a visual check of the work area and containment, moisture verification, and air sampling inside containment against an outdoor control, evaluated against IICRC S520, the industry standard for professional mold remediation. Commercial and multi-unit clearance is quoted by containment count.

Pricing

Laboratory results normally return in 1 to 3 business days and the report follows within a day of that. When a lease start date is driving the schedule, say so at booking and we will tell you honestly whether the date is achievable before you commit.

Ground-contact units carry the exposure.

Why the local building stock produces these calls

Spokane County has 241,434 housing units against a population of 558,344, and in the City of Spokane roughly 27% of housing predates 1950. A large share of the rental inventory is converted or aging stock: unconditioned crawlspaces with failed or missing vapor barriers, cast iron and galvanized supply and waste lines well past design life, and stacked plumbing walls where one failure wets three units.

The failure mode here is event-driven, not climate-driven. Spokane averages 17.2 inches of rain and 43.9 inches of snow annually and Coeur d'Alene 26.6 inches and 42.4 inches, so the Idaho side is meaningfully wetter. Neither is a humid climate. What generates the work is hard freezes and burst supply lines, ice dams driving meltwater into wall assemblies, spring melt into below-grade space, and appliance failures, which happen year round. Nationally, water damage and freezing claims run about 1.61 per 100 insured properties per year at an average severity near $13,954, roughly one in sixty annually, and the American Housing Survey indicates actual leak-related damage runs five to six times the claim rate because most of it is never claimed.

Questions owners and managers ask

Do you do move-in baselines? Yes, and for any unit with water history it is the single most useful document you can hold. It is far more defensible than a report ordered after a dispute begins.

Who receives the report? Whoever engages us. If you hire us, it goes to you. We will explain method to a tenant on site and answer factual questions, and we take no position on fault.

Can you handle a whole building? Yes. Send the unit count, layout and stack configuration. Common area and shared-chase sampling is a different design than a single unit and we will walk you through it before you commit.

What if the tenant refuses entry? That is between you, the tenant and your notice requirements. Flag it in advance so we can hold the slot.

Can you validate a remediation bid? Yes. We map moisture and document the boundary of affected material, which gives you something to measure a proposed scope against. We never bid the work ourselves.

Do you work directly for tenants? Sometimes, and we do the job the same way. The method and the report do not change based on who pays. That is the point of independence.

Set up multifamily testing

Send a unit list or a property address with unit count. We will return a written scope, a per-unit price, and a schedule that fits your notice requirements.