Mold in My Apartment: A Renter’s Step-by-Step Guide

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Finding mold in an apartment raises two questions at once: is it a health concern, and whose job is it to fix? Renters usually control less of the building than homeowners do. They cannot open a wall, replace a roof or service the building’s ventilation, but they can do a great deal to protect themselves and to make sure the problem gets fixed. If you are typing “mold in my apartment” into a search bar, this guide gives the practical sequence: document what you see, notify the landlord in writing, limit exposure, clean only what is small and allowed, adjust daily moisture habits, and recognize when the source is the building rather than the household. It summarizes EPA and CDC guidance current as of 2026. It is not legal advice: tenant rights depend on your lease and on current state and local law, so check current Colorado law or a tenant resource before relying on any legal point here. Anyone with symptoms should talk to a physician.

Part of our Types of Mold guide — start there for the full picture →

First Steps When You Find Mold in Your Apartment

The order of the first few actions matters, because the record created in the first day or two often shapes everything after it. A calm, organized response also tends to get faster repairs than an angry phone call.

1. Look before you touch. Note where the growth is, roughly how large an area it covers, and whether there are signs of water: staining, bubbling paint, soft drywall, a damp smell, or drips.
2. Photograph it with dates. Take wide shots that show the room and close-ups that show the growth. Most phones store the date in each photo’s details, but it also helps to include something dated in a few frames or to keep a written log.
3. Check for an active leak. A dripping pipe, an overflowing appliance or water coming through the ceiling is urgent and should be reported immediately by phone as well as in writing.
4. Notify the landlord in writing. Email, a tenant portal message or a dated letter creates a record. Keep copies.
5. Limit exposure while you wait, especially for anyone in a sensitive group (covered below).

EPA’s Brief Guide to Mold, Moisture and Your Home speaks directly to renters: it says to report all plumbing leaks and moisture problems immediately to the building owner, manager or superintendent, and that where persistent water problems are not addressed, renters may want to contact local, state or federal health or housing authorities. That is a short instruction, but it captures the core of a renter’s role: report promptly, and escalate if nothing happens. Common locations and causes in rental units are covered in the guide to mold in an apartment.

Documenting the Problem and Notifying the Landlord

A good record protects the tenant, helps the landlord understand the problem, and gives any later inspector or housing authority something concrete to work from. It does not need to be elaborate. It needs to be consistent and dated.

What to record

• Photos and video, repeated every week or two, from the same angles, so changes in size are obvious.
• A short written log with dates: when the mold was first noticed, when it was reported, every response, and every visit by maintenance.
• Moisture clues: window condensation, a musty smell, humidity readings, recent leaks, or water stains above or around the area.
• Damage to belongings, such as stained clothing, mattresses or boxes, with photos.
• Health notes, if anyone in the household is having symptoms, and any medical visits. Keep this factual and private.

How to write the notice

A written notice works best when it is short, specific and polite. It should state the unit address, where the mold is, roughly how large the area is, when it was first noticed, any known or suspected water source, and a request for inspection and repair. Attach two or three photos. Ask for a reply by a reasonable date and say how maintenance can arrange access.

Avoid diagnosing the mold type or making medical claims in the notice. Phrases such as “visible mold about the size of a dinner plate on the bathroom ceiling, near a recurring water stain” are more useful to a landlord than “toxic black mold.” Federal guidance does not require knowing the species. CDC’s mold page says that if you see or smell mold, you should remove it, and that you do not need to know the type of mold.

If there is no response, send a follow-up in writing that refers to the first notice by date. Keep it factual. Repeated, dated requests make a much stronger record than a single message.

Limiting Exposure While You Wait

Mold affects people differently. CDC’s mold page says exposure to damp and moldy environments may cause a variety of health effects, or none at all. For some people, it can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash. CDC adds that people with asthma or who are allergic to mold may have severe reactions, and that immune-compromised people and people with chronic lung disease may get infections in their lungs from mold.

That list defines the sensitive groups a renter should think about first: anyone in the home with asthma, mold allergy, a weakened immune system or chronic lung disease. Infants, older adults and people recovering from illness are reasons for extra caution too. Practical steps while repairs are pending include:

• Keeping the door to the affected room closed, and not sleeping in a room with active growth if another room is available.
• Moving bedding, clothing and stored items away from the affected wall or ceiling.
• Avoiding scraping, sanding or dry-brushing moldy surfaces, which can release spores.
• Improving ventilation with exhaust fans and, when weather allows, open windows.
• Talking to a physician if symptoms appear or get worse, and mentioning the mold exposure.

For an overview of symptom patterns renters often ask about, see the guide to mold in apartment symptoms and the explainer on black mold symptoms. Neither replaces medical advice.

What Renters Can Safely Clean

Small, surface-level mold in a rental is often something a tenant can clean, as long as the lease allows it and the landlord has been told. Some leases assign routine cleaning of bathrooms and windowsills to the tenant. Others require the landlord to handle any mold. If the lease is unclear, ask in writing before cleaning anything beyond a light wipe-down, and photograph the area first so the record shows what was there.

EPA’s Mold Cleanup in Your Home page sets the size guideline: if the moldy area is less than about 10 square feet, roughly a 3-foot by 3-foot patch, in most cases you can handle the job yourself. If there has been a lot of water damage, or mold covers more than 10 square feet, EPA points to its guidance for larger remediation and says that anyone hiring a contractor should make sure the contractor has experience cleaning up mold. In a rental, larger growth is almost always the landlord’s job to arrange.

For small areas, EPA’s tips include:

• Fix plumbing leaks and other water problems as soon as possible, and dry all items completely.
• Scrub mold off hard surfaces with detergent and water, then dry completely.
• Recognize that absorbent or porous materials, such as ceiling tiles and carpet, may have to be thrown away if they become moldy.
• Do not paint or caulk over moldy surfaces. Paint applied over mold is likely to peel.

EPA’s Brief Guide also covers protective gear: an N-95 respirator, long gloves and goggles without ventilation holes to avoid breathing in spores or getting them in the eyes. CDC’s mold page adds that if bleach is used, it should be no more than 1 cup of household laundry bleach per gallon of water, never mixed with ammonia or other cleaners, with windows and doors open for fresh air. EPA’s Brief Guide notes that a biocide such as chlorine bleach is not recommended as a routine practice during mold cleanup, so plain detergent and water is a reasonable first choice for most small spots.

Anyone in a sensitive group should not do the cleaning. Neither should a renter dealing with growth inside walls, in the building’s ductwork, or after sewage or contaminated water. EPA says contaminated-water damage calls for a professional with experience in that kind of cleanup, and that an HVAC system suspected of mold contamination should not be run until it is checked. Bathroom-specific tips are in the guide to black mold on a bathroom ceiling.

Condensation and Humidity Habits That Help

Many apartment mold problems start with ordinary indoor moisture rather than a leak. Showers, cooking, drying laundry indoors, aquariums, houseplants and even breathing all add water vapor to the air. In a small, tightly sealed unit, that moisture can build up and condense on the coldest surfaces: windows, exterior corners, closet walls and the back of furniture pushed against an outside wall.

EPA’s Brief Guide recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent, and notes that relative humidity can be measured with an inexpensive humidity meter. CDC’s mold page suggests keeping humidity as low as possible, no higher than 50 percent, all day long. A small hygrometer placed in a bedroom and a bathroom shows whether daily habits are keeping levels in that range.

Habits that help, drawn from EPA and CDC guidance:

• Run the bathroom fan or open the window while showering, and leave the fan on for a while afterward.
• Use the range hood or open a window when cooking or running the dishwasher.
• Make sure the clothes dryer vents outside; avoid drying large loads on racks indoors in winter.
• Use an air conditioner or dehumidifier when needed.
• Pull furniture a few inches away from exterior walls so air can move behind it.
• Wipe condensation from windows and sills promptly. EPA says that when condensation collects on windows, walls or pipes, act quickly to dry the surface and reduce the moisture source.

Colorado’s Front Range climate is dry for much of the year, which helps, but winter brings a specific pattern: cold outdoor air chills window glass and exterior walls, and a warm, humid unit inside produces condensation on those surfaces. Older single-pane windows and poorly insulated corners are especially prone to it. The guide to window condensation explains why it happens and how to reduce it.

When the Problem Is the Building

Household habits can only do so much. When mold keeps returning despite good ventilation and humidity in the 30 to 50 percent range, the source is often something the tenant cannot reach. Common building-side causes include:

• Plumbing leaks inside walls or from the unit above.
• Roof, window or siding leaks that let rain or snowmelt into wall cavities.
• Ventilation problems, such as a bathroom fan that is not vented outside or does not run.
• HVAC issues, including clogged condensate drains, dirty drip pans or contaminated ducts. EPA’s Brief Guide lists keeping air conditioning drip pans clean and drain lines flowing among its prevention tips.
• Foundation or grading problems in garden-level or basement units, where water collects against the building.
• Hidden mold, which EPA says can be suspected when a building smells moldy but the source is not visible, or after known water damage.

These problems need the landlord, and often a contractor or inspector. Basement and garden-level units carry another consideration as well: radon tends to be higher on lower floors, so renters in those units may also want to read about radon in apartments.

Situation, renter action and landlord responsibility

The table below summarizes common situations. The landlord column is a general description of how these issues are usually handled, not a statement of law. Responsibilities depend on the lease and on current state and local law.

Protecting belongings and records during repairs

Building-side repairs can take time, and the work itself can disturb mold. While a leak is being traced or a wall is opened, renters can ask in writing how the work area will be contained, how long the job is expected to take, and whether the affected room should stay closed. EPA’s Brief Guide notes that investigating hidden mold can release spores, giving the example that removing wallpaper with mold on the underside can lead to a large release, which is one reason containment questions are reasonable to ask.

Move clothing, bedding, electronics and paper items out of the work area before repairs begin, and photograph anything already stained or damaged. EPA notes that porous materials such as carpet and ceiling tiles may have to be thrown away once moldy, and the same is often true of mattresses, upholstered furniture and cardboard boxes. Renters insurance policies vary in whether they cover mold damage to personal belongings, so check the policy wording and ask the insurer directly rather than assuming. Keep receipts for anything replaced and add them to the log, alongside dates of every repair visit and any days the unit or a room could not be used.

Tenant Rights in Colorado and Testing Questions

Colorado’s warranty of habitability can cover mold in some circumstances, particularly where mold is linked to water intrusion or other conditions that affect health or safety and the landlord has been notified. The details matter: what counts as a qualifying condition, what notice is required, what timelines apply, and what remedies a tenant may have all been the subject of changes to Colorado law in recent years. Check current Colorado law or a tenant resource, such as a local legal aid organization or tenant hotline, before withholding rent, breaking a lease or taking any other step with legal consequences. Nothing in this guide is legal advice.

Renters with housing assistance may have additional inspection standards that apply to the unit. The Section 8 home inspection checklist outlines the kinds of conditions those inspections look at.

Does a renter need a mold test?

Usually not when mold is visible. EPA’s Brief Guide says that in most cases, if visible mold growth is present, sampling is unnecessary, and that because no EPA or other federal limits have been set for mold or mold spores, sampling cannot be used to check a building’s compliance with federal mold standards. CDC’s mold page also says it does not recommend mold testing, noting that there are no set standards for acceptable quantities of mold in a home and that the best approach is to safely remove the mold and prevent future growth.

Testing can still have a role. It can help document a musty smell with no visible source, support a request for investigation of hidden mold, or check whether an area has been adequately cleaned. EPA’s Brief Guide notes that surface sampling may be useful for that last purpose, and that sampling should be done by professionals with specific experience. For lower-cost options and their limits, see the guide to an affordable mold test. Professional inspection pricing is covered in the guide to certified mold inspector cost.

Knowing when cleanup is finished

EPA’s Brief Guide gives a useful checklist for judging whether a remediation is complete: the water or moisture problem has been completely fixed, visible mold and moldy odors are gone, the area shows no signs of water damage or mold growth when revisited shortly after cleanup, and people can occupy the area without health complaints. Renters can use the same checklist to decide whether a landlord’s repair actually solved the problem, and should keep documenting if it did not.

For more on how mold develops, how different types look and when to call a professional, see the mold inspection guide and the mold types hub.

References

• A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency
• Mold Cleanup in Your Home — U.S. Environmental Protection Agency
• About Mold and Your Health — Centers for Disease Control and Prevention

Not sure whether the mold in your unit is a habits problem or a building problem? Drop us a line and we can help you think through the options.