Mold on Ceiling: How to Clean It and Prevent Regrowth

To get rid of mold on a ceiling, stop the water source first, then clean a small patch and dry it completely within 24 to 48 hours. The Environmental Protection Agency (EPA) says mold control comes down to moisture control, so cleaning a ceiling while the leak continues leaves the moisture in place for new growth. Moisture can come from roof materials above the ceiling and from plumbing.

This site owns no measuring instruments and has tested nothing, so every number on this page comes from a published source named in the sentence. The guidance comes from EPA, the Centers for Disease Control and Prevention (CDC), Harvard Health, and the University of Minnesota and University of Georgia extension services.

At The Indoor Report, we compile and explain published guidance on indoor air, water, humidity and mold. Our rule on this site is to tie each figure to a named source, and to say so when a source is silent.

What to Do About Mold on a Ceiling

Stop the water source first, then protect yourself, size the patch, clean or discard, dry, and watch for return. Mold grows where there is moisture (CDC), so cleaning before the water stops leaves the moisture in place.

Use the patch size to decide who does the work. The EPA gives the limit as roughly a 3 ft by 3 ft patch. The steps for doing it yourself are in how to get rid of mold.

EPA says to dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. University of Georgia Extension says to discard non-structural items that cannot be dried in that time.

• Stop the water source. EPA says to fix plumbing leaks and other water problems as soon as possible.
• Size the patch. In most cases, EPA says, a homeowner can handle a moldy area under about 10 square feet.
• Clean hard surfaces with detergent and water, or discard porous material that cannot be cleaned.
• Dry the area within 24 to 48 hours, and dry all items completely.

Ceiling Mold Can Trace to Water Above or Moisture in the Air

Mold sources named in the published guidance include water coming from above, cold surfaces that collect moisture, steam from bathrooms and cooking, and humidity in the house. EPA says mold is usually not an indoor problem unless spores settle on a wet or damp area and begin to grow.

Roof leaks are one source to check. EPA says moisture problems can arise in roof materials above ceiling tiles because of roof leaks or insufficient insulation. CDC lists leaks in roofs, windows and pipes as places where mold grows.

Plumbing leaks are another source. CDC lists leaks around pipes as a place mold grows, and EPA says water in a home can come from many sources, including outside leaks.

Cold surfaces and humidity are another source. EPA says that as temperature goes down, air holds less moisture, so moisture can form on cold surfaces and encourage mold. Condensation can also be a sign of high humidity (EPA). For the cold-surface case, see can condensation cause mold and mold on walls.

Showers and cooking add moisture to indoor air (EPA), and Harvard Health names excessive bathroom moisture as a common cause of mold. University of Minnesota Extension adds that breathing, showering and cooking all add moisture, and that the more people living in a home, the more likely molds will grow. The bathroom case has its own page: see mold in a bathroom.

Telling Mold Apart from Dirt and Mildew

Dirt and dust wipe off easily, and mold does not. Mold has a distinct damp smell and often looks furry or velvety, according to Ursinus College Environmental Health and Safety, a single campus source. Harvard Health lists fuzzy, discolored or slimy patches in moist areas, and a musky odor, as signs.

EPA says mildew refers to certain kinds of mold or fungus and is often used generically for mold with a flat growth habit. It often lives on shower walls, windowsills and other high-moisture places.

If the source is not obvious, Harvard Health says to look behind carpets, wallpaper, cabinets and walls. CDC does not routinely recommend mold test kits.

EPA says not to paint or caulk moldy surfaces.

Cleaning a Small Patch Safely

Scrub mold off hard surfaces with detergent and water, then dry the surface completely (EPA). University of Minnesota Extension prefers a stiff brush with hot water and an ammonia-free detergent for small areas.

EPA's remediation guide says to use an N-95 respirator for a small area, to always use gloves and eye protection, and to choose gloves that reach mid-forearm. University of Georgia Extension lists rubber gloves, unvented protective eyewear and an N-95 or higher respirator.

• Respirator: an N-95 respirator for a small area (EPA), or an N-95 or higher respirator (University of Georgia Extension).
• Gloves: long enough to reach mid-forearm (EPA), or rubber gloves (University of Georgia Extension).
• Eyes: goggles that keep dust and small particles out. EPA says safety glasses and goggles with open vent holes are not acceptable.

Bleach Recommendations Differ Between Agencies

The sources disagree on bleach. EPA does not recommend bleach as a routine practice during mold cleanup, while CDC and Harvard Health permit a bleach solution on hard surfaces.

EPA says killing mold is not enough, because dead mold can still trigger allergies and must be removed. Professional judgment may justify a biocide such as chlorine bleach, for example when immune-compromised people are present (EPA).

University of Georgia Extension advises testing bleach on an inconspicuous spot first. It also says not to use bleach on metals or near the air conditioning system. For more on bleach and vinegar, see bleach vs vinegar for mold.

Porous Ceiling Materials Often Need Discarding

Ceiling tiles are one case. EPA says absorbent or porous materials such as ceiling tiles and carpet may have to be thrown away if they become moldy. University of Georgia Extension says ceiling tiles are seldom salvageable once water and mold have damaged them.

Drywall is handled differently. CDC lists drywall among the materials mold can grow on. EPA's remediation guide says not to use wet vacuums on porous materials such as gypsum board, and University of Georgia Extension recommends a HEPA (high-efficiency particulate air) vacuum on drywall.

Discard what cannot be dried. EPA's remediation guide says porous wet materials with mold growing on them may have to be discarded, and that unsalvageable material should be double-bagged. Harvard Health notes that porous items such as carpets and ceiling tiles may need discarding because they cannot be fully cleaned.

When to Hire a Professional for Ceiling Mold

Hire a professional when the patch is larger than about 10 square feet or after a major flood (Harvard Health), and consider one when the mold may be hidden (EPA). EPA's remediation guide says to consider an experienced professional for suspected hidden mold, and structural damage calls for a structural engineer.

Harvard Health also says to start by calling a professional, such as a plumber, to fix the underlying problem. For larger jobs, see mold remediation and mold inspection.

EPA's advice is to pick a contractor with experience cleaning up mold, and to ask for references. EPA has no certification program for mold inspectors or remediation firms and keeps no list, though some states may require certification. Ask about qualifications, training and experience.

Harvard Health says to look for certification from NEHA, AIHA, IICRC or ACAC, the four bodies it names by initials. ANSI/IICRC S520 is a procedural standard for remediation of mold-damaged structures and contents, written for the remediation industry.

Keeping Humidity Down to Prevent Regrowth

EPA's brief guide says to keep indoor humidity below 60 percent, ideally between 30 and 50 percent relative humidity (RH). CDC says humidity should be no higher than 50 percent.

Bath, kitchen and dryer fans vent moist air outside, according to University of Minnesota Extension. It recommends using them during cooking and showering, or opening a window if there is no fan. Harvard Health says to run the bathroom fan during showers or open a window.

EPA says to use exhaust fans or open windows when cooking and running the dishwasher. More ventilation and more frequent cleaning help in damp areas such as bathrooms (EPA).

EPA says to fix plumbing leaks and other water problems as soon as possible, and to dry all items completely. Condensation on window glass can be a sign of high humidity, so see condensation on windows. For humidity readings, see the hygrometer guide, and for a wider set of steps, see how to prevent mold.