Mold in a Lynn apartment: who has to fix it, how fast, and what you can do

Massachusetts is one of the few states whose housing code names mold directly. Since the 2023 rewrite of the State Sanitary Code, every owner must keep the building watertight and “free from excess moisture or the appearance of mold,” must dry every surface within 48 hours of a leak or flood, must vent every bathroom to the outdoors, and may not rent a damp basement as living space at all. None of that requires a lab test — the appearance of mold is the violation. What the code does not do is settle the argument automatically: whether a given patch of mold “endangers health,” the finding that opens the fastest remedies, is the inspector's call. This page lays out each rule with its section number, the inspection that turns a complaint into a record, the dollar remedies at today's Lynn rents, the health guidance the CDC and EPA actually give, and Census data on how old Lynn's rental stock is. Every legal claim links to its source.

What this page is: the rules that decide who deals with mold and the water behind it in a Lynn rental, each linked to its official source, next to the health guidance the public agencies actually give and Census data on how old the city's rental stock is. It is not legal advice and not a health diagnosis — when it matters, read the linked source, use the free legal help on our tenant rights page, or see a doctor.

The Sanitary Code names mold outright: the building must stay watertight and “free from excess moisture or the appearance of mold”

105 CMR 410.500(A) requires every owner to maintain all buildings and structural elements “in good repair and in every way fit for the intended use,” including “protected from wind, rain and snow, and are watertight, free from excess moisture or the appearance of mold, and pest resistant.” The 2023 rewrite of the code (effective May 12, 2023) is what put the word mold in the text; before it, tenants argued mold through general “structural elements” and dampness language. Two things follow. First, the appearance of mold is itself the violation — a photograph and an inspector's eyes are enough, no species name or spore count required. Second, “excess moisture” is a violation before any mold grows, so a wet wall or a condensation-soaked window frame is reportable on its own. The duty runs to the “owner,” which 410.020 defines to include anyone with “care, charge or control” of the dwelling — the management company answers for it, not only the name on the deed. Source: 105 CMR 410.500 — Owner's Responsibility to Maintain Building and Structural Elements · 105 CMR 410.020 — Definitions · 105 CMR 410.000 — State Sanitary Code, Chapter II (Mass.gov)

After a leak or a flood, the owner has 48 hours to get every surface dry

The same section adds a clock that did not exist before 2023. 410.500(B): “In the event of leaks and flooding, the owner shall ensure all surfaces have been dried within 48 hours from the time they are notified or the end of the event, whichever is sooner.” Read the trigger carefully — the clock starts at your report or at the moment the water stops, whichever comes first, so a leak you sat on for a week does not buy the owner a week. The number is not arbitrary: the EPA's own guidance is that wet materials dried within 24–48 hours will, in most cases, not grow mold. The practical rule that falls out of it is to report water in writing the same day you see it, with a photo and a timestamp, because the 48 hours are measured from that message. Source: 105 CMR 410.500(B) — 48-hour drying requirement · U.S. EPA — A Brief Guide to Mold, Moisture, and Your Home

“Chronic dampness” has a legal definition — and it bars a damp basement from being a bedroom

410.020 defines chronic dampness as “the regular and/or periodic appearance of moisture, water, mold or fungi.” The definition does its main work in 410.402: no room or area may be used for habitation if more than half of its floor-to-ceiling height is below the average grade of the adjoining ground and it is subject to chronic dampness. That is the rule for garden-level units and converted basement bedrooms, of which Lynn — where 39% of renter-occupied homes were built before 1940 — has many. A below-grade room that gets damp on a recurring basis is not lawful living space, whatever the lease calls it, and a lease that rents it as such is renting something the code says cannot be occupied. Source: 105 CMR 410.020 — Definitions (“Chronic Dampness”) · 105 CMR 410.402 — Grade Level

Bathrooms must vent to the outdoors: a window that opens, or a fan that moves five air changes an hour

410.280 requires the owner to provide, for every habitable room and every room containing a toilet, bathtub or shower, ventilation to the outdoors: either windows, skylights, doors or transoms in the exterior walls or roof that open to at least 4% of the room's floor area, or mechanical ventilation exhausting at least two air changes per hour for habitable rooms and five for bath, toilet or shower rooms. A bathroom with neither — a sealed window and no working fan — is a code violation before any mold shows, and it is the violation to cite when the mold is on a bathroom ceiling, because a fan that was never installed or never worked is an owner's problem, not a housekeeping one. The same section covers a bedroom whose only window is painted shut. Source: 105 CMR 410.280 — Natural and Mechanical Ventilation

How to make it stick: ask Lynn's inspectors in writing, and know that mold is a judgment call on the “endangers health” list

The enforcement machinery is the one every repair uses. Under 105 CMR 410.600 the local board of health “shall inspect” a unit on any occupant's request; in Lynn that request goes to the Inspectional Services Department. The inspection report is the record, and the record is what the money remedies run on. Here is the honest complication: the code's list of “conditions deemed to endanger or impair health or safety” (410.750) does not name mold or dampness. It names roof, foundation and structural defects that may expose the occupant to harm (K), conditions left uncorrected for five or more days (O), and “any other violation” the inspector finds to endanger health (P). Whether your mold lands on that list is the inspector's finding — and that finding is what opens c.111 §127L: once violations that may endanger health or safety are certified and the owner has written notice, the owner has five days to begin repairs and fourteen to substantially complete them, after which you may have the work done and deduct up to four months' rent in any twelve-month period. Withholding rent under c.239 §8A is the other lever, argued as a defense. Both are laid out step by step, with the per-ZIP dollar table, on the repairs page. Source: 105 CMR 410.600 — Inspection upon Request · 105 CMR 410.750 — Conditions Deemed to Endanger or Impair Health or Safety · M.G.L. c.111 §127L — repair and deduct · M.G.L. c.239 §8A — rent withholding as a defense · Lynn Inspectional Services Department

Testing is the wrong first move — the CDC and the EPA both say fix the water

Neither federal health agency wants you to buy a mold test. The CDC's position is that it “does not recommend mold testing”: reactions vary from person to person and there are no accepted standards for how much mold in a home is too much, so the useful step is to remove the mold safely and stop the moisture. The EPA says the same — if mold is visible, sampling is unnecessary — and gives the working numbers: a patch under about ten square feet (roughly three feet by three) is usually a do-it-yourself cleanup, indoor humidity should stay below 60% and ideally between 30% and 50%, and wet materials dried within 24–48 hours generally will not grow mold. On health, the CDC lists a stuffy nose, sore throat, coughing or wheezing, burning eyes and skin rash for the general population; people with asthma or a mold allergy may react severely, and people who are immune-compromised or have chronic lung disease can develop lung infections. In Massachusetts the legal fit is exact: the code violation is the appearance of mold or excess moisture, so the evidence that matters is the photograph and the inspection report, not a lab number. Source: CDC — About Mold and Dampness · U.S. EPA — A Brief Guide to Mold, Moisture, and Your Home

What's on you: the moisture you make, and the report you send

The code puts the structure, the drying clock and the ventilation on the owner. What an owner can point back at is occupant behavior — showers with the fan off, laundry drying indoors, furniture pushed against an exterior wall, a vent taped over — which is why the EPA's numbers double as your defense: run the fan or open the window while you shower, keep humidity under 60%, and report every leak or condensation problem in writing the day you find it. That written report is not paperwork for its own sake. It starts the 48-hour drying clock, it is the notice the repair-and-deduct statute requires, and it is the document Massachusetts' retaliation law protects — a landlord who answers a code complaint with a notice to quit or a rent increase has to overcome a presumption that the response was retaliatory. Source: U.S. EPA — A Brief Guide to Mold, Moisture, and Your Home · 105 CMR 410.500 — owner's duties (structure, drying, moisture) · M.G.L. c.186 §18 — protection against retaliation

How old Lynn's rental stock is, by ZIP — the envelope, the plumbing, and the bathrooms

Age doesn't make mold; water does. But the age of a building says a lot about the things the rules above target — the roof and foundation that must stay watertight, the plumbing behind the walls, and whether a bathroom was built with the exhaust fan or opening window the code now requires. Citywide, Lynn's median home was built in 1945; of its 18,021 renter-occupied homes, 39% predate 1940 and 78% predate 1980 (2019–2023 ACS 5-year):

Honest caveat: no public dataset measures mold or dampness by ZIP code — not the Census, not the state, not the city. The table is the U.S. Census Bureau's American Community Survey count of renter-occupied homes by the decade they were built, a proxy for the age of the building envelope and its systems, nothing more. A 1920 three-decker with a new roof and a vented bathroom is dry; a 2005 building with a bad flashing detail is not. The same figures, read for lead paint, are on the lead-paint page.

Where a mold problem usually goes next

The mechanics of getting anything fixed — the inspection request, the written notice, and the dollar remedies run per ZIP at today's rents — are on the repairs page; this page is the mold-specific layer on top of it. If a leak has also knocked out water, heat, or power, the utilities page covers the shutoff rules; if the answer to your report is a notice, a raise, or a suit, the retaliation page covers the law that protects the report itself; and whether a policy would have covered the ruined belongings is on the renters-insurance page. If the unit isn't worth the fight, each Lynn ZIP's current average (01905, 01902, 01901) says what moving costs instead.

Page last updated September 8, 2026 · rent index data through July 2026.