How does mold develop on the ceilings in my home?

Mold is a living organism that belongs to the kingdom of Fungi. They are found in the form of small organisms that can be white, black, green, orange, or purple. These tiny organisms can exist anywhere indoors and outdoors. Usually, they are harmless when they live in small amounts. But when they land on a wet or humid spot in your home like ceilings, ceiling mold can start to grow to a large extent. They produce spores that you might breathe in. If you inhale a large number of spores, that can be sensitive and dangerous for you. They can cause illness for you.

How common is mold in your buildings?

Mold is commonly found in buildings and homes. They grow in those places where moisture exists in large amounts. Such as leaks in roofs, pipes, windows, or where there has been flooding. Mold grows well on cardboard, paper products, drywall, fabrics, ceiling tiles, and upholstery. They can also grow in dust, wallpaper, paints, or insulation.

Common indoor mold types are:

  • Penicillium
  • Cladosporium
  • Aspergillus

How do molds get in indoor environments and how they grow?

They can enter your home through windows, vents, open doorways, air conditioning, and heating systems.  Spores can also attach themselves to shoes, clothes, bags, and pets for carrying mold indoors.

When a spore drops on the moisturized place such as leakage in roofs, pipes, pots, and walls, etc., it will grow. Building materials can also encourage mold to grow because building materials involve some suitable nutrients for mold production.

Ceiling Mold

Ceilings can face moisture and mold problems for a variety of reasons. Whenever you see mold on the ceiling of your home, then you may have a humidity – condensation or water intrusion problem. A water leakage above the ceiling causes mold. Usually, mold grows behind walls, but sometimes you see growing on the ceilings. To ensure that mold is rising above the ceilings in your home, look for water staining on the ceilings. A borescope can be used to look inside the ceiling.  Beyond the insulation, you can see small patches of mold growth on the drywall paper. There can be large colony of mold on the other side, maybe black mold or green mold. The two main issues and causes of mold are given below:

  • Humidity
  • Water intrusion – Liquid moisture


The concentration of water vapor present in the air refers to as humidity.  We’ve all taken a hot shower and seen the moisture condense on the surface of the mirror.  Humidity problems happen when warm moisture interacts with cool surfaces. Due to this, the process of condensation and interior mold growth becomes active when moisture droplets condense on the roof. The lack of ventilation and high humidity is most common in bathrooms or the kitchen. Moisture droplets land (condense) on the surfaces and create enough moisture for mold spores to begin a growth phase.  Other areas that create elevated humidity are the dishwasher and the clothes dryer.  Both cause humidity within your home if the drains or ducts are blocked this can be a real problem. This type of moisture allows for the rapid growth of mold.

Building Conditions that lead to condensation or eventually mold growth:

  • Poor insulation on the attic
  • Plaster walls or ceilings (usually much cooler)
  • Chipping or old and worn painted surfaces.
  • Long and hot showers
  • Poor ventilation
  • Closed Windows and doors.

Water Intrusion

Water intrusion or leaks happen due to direct exposure to water, i.e., roof leakage or plumbing failures. Usually, mold growth is due to a combination of both factors, humidity, and liquid moisture. Sometimes, ceiling mold occurs due to extensive flooding, although the water never touched the ceiling, it still happens. It only happens due to the extremely high humidity created by the flood throughout the entire home. You may see and experience the growth of mold on picture frames, furniture, and the surface of walls.

During a hard rain, you might experience:

  • Misdirected water because of clogged gutters
  • Cracked or broken exterior stucco
  • Incorrectly installed windows
  • Incorrect or old flashing problems
  • Roofing shingle that loosens or gets blown from the surface.

Roof leaks from rain and water intrusion

Roof leakage is a problem that we have to face in any weather, but a roof that suddenly begins to leak due to heavy rainstorms can be a severe problem for us. Water may start seeping through a penetration point and eventually drip onto the ceiling. It usually has to work its way through the insulation, so you may not notice water intrusion right away.

Causes of a roof leakage:

  • Plumbing
  • Chimney
  • Metal corrosion
  • Condensation
  • Skylights
  • Degraded shingles

Symptoms of water damage occur caused by roof leakage:

  • The discoloration is yellow/brown
  • Mold follows a circular pattern
  • Confined to a single region – localized

Mold  could be due to an air conditioning system in the attic

Moisture growth becomes active due to the mixing of hot and cold temperatures an air handling unit. When we have an air conditioning system in the attic, the same case happens, hot and cold temperatures mix and create moisture that causes mold growth. Similarly, cold beverages sweat and create condensation; due to this effect, HVAC systems create moisture and eventually mold.

Air conditioning systems usually discharge water, and if the drain system is blocked, water can drip in the building material and causes mold growth.

Solar panels in the roof can cause mold

Solar panels create a shaded environment, out of the direct sunlight. Penetration points are put in the roof and over the years the waterproofing systems tend to fail.  Add to that the additional weight caused by the solar panel system, and water intrusion is bound to occur at some point.

PEX Plumbing system Failure

PEX plumbing system failures have been observed and well known because it has been used for many years. Its primary failure is pipe linking and fitting. These failures usually run in the new homes, or the system needs repairing and maintenance in over homes. Pipes are exposed to chlorine, which is within the water, exposed to direct sunlight before its installation and this causes failures. Moreover, PEX pipes are at risk when it comes in contact with petroleum products or oxygen. If the PEX system is fitted in the attic and it runs to failure, the water drips in the building materials can produce water intrusion in your ceiling and walls. This moisture will activate the growth of mold in the attic or surrounding walls.

Mold growth on bathrooms ceiling

Cold climates or high humidity are most likely to suffer from mold in the bathroom ceiling. When the warm, humid air of the hot shower contacts the cold surface of the roof, it causes condensation. If the bathroom doesn’t have a better quality exhaust fan, the condensation will eventually lead to mold growth at a rapid pace. Primarily if the toilet is located upstairs, it can cause mold on the ceiling. This the main reason that we noted the mold growth on the ceilings before it accumulates on the walls. It usually happens in multi-story apartments and business complexes. Water always follows the least resistance path and often flows in the downward direction.


Verifying the cause of mold on the ceiling

There are two ways to verify the cause of mold growth. If you have access to the above area of the bathroom, simply pull back the insulation. If the side facing the attic ( backside of the sheetrock) shows the sign of mold growth- definitely you are dealing with roof leakage.

In another situation, if you don’t have access to the attic, you can simply use the moisture meter to verify the moisture content. Usually, a moisture meter will not indicate the moisture due to condensation. So, if the meter shows high water content, you are dealing with a roof leak. To get better and accurate results to perform this task after a recent rain event.

Identify the extent of mold growth

As we know, mold growth depends on two main factors. So, here we will discuss the extent of mold growth depending upon these factors.

Condensation based ceiling mold

The extent of the mold growth can be observed or verify from the interior part of the home. So, stand in the middle of the room and observed it well. If there is no mold growth, there will be no chance that mold can exist on the other side of the ceiling. In these situations, the mold testing technique is best to apply.

Water Intrusion – based ceiling mold

Usually, liquid water enters into a building by the leakage of water pipes or by an envelope, roof leakage, condensation related to HVAC systems. It tends to soak into the materials which have pores such as drywall. It also tends to soak into semi-porous materials like wood framing. The backside of the sheetrock contains more mold as compared to the side facing the room.

Visual observation of the backside of the ceiling is the only method to identify the extent of mold growth accurately and efficiently.


How do molds affect people’s health?

Exposure to moldy environments can cause a variety of health problems. Some people are sensitive and have allergies to molds.  Some people are sensitive to mold. For those people, facing mold can lead to symptoms such as wheezing, stuffy nose, and itchy or red eyes, or skin. People who have allergies to mold or suffering from asthma may have to face some severe and intense reactions. These reactions may include shortness of breath and fever. Farmers working around moldy environments may have to face these severe reactions.

The Centers for Disease Control and Prevention (CDC) has published a post for the public that shows that exposure to mold caused asthma in some children.  In 2004 the IOM (Institute of Medicine ) found that early exposure to mold causes cough, wheeze, etc. in 2009, the WHO issued guidelines for Indoor Air Quality and Dampness.  WHO recommends that improve housing conditions can reduce respiratory allergies as well as morbidity from asthma.

There is no specific blood test for mold. Some physicians can perform allergy testing for possible allergies to mold, but they don’t have any clinically proven test. They can’t reveal that when or where a particular mold took place. So, if you have mold in your home, it’s time to call a professional to remove mold and moisture.

What are the tips to control mold around the house?

We must protect our homes from mold growth to avoid sensitive and severe reactions to our health. The following tips can be helpful for you to control mold around your house.

  • Try to keep indoor humidity below 60%
  • Use fans to achieve better ventilation.
  • Clean your air conditioning drip pans
  • A hygrometer can check the humidity level. So, use it.
  • Use dehumidifiers, especially in hot, humid climates
  • Try to dry wet area as soon as possible (24-48 hours) to prevent mold growth

Remediating mold growth in ceilings

Firstly, identify whether the water damaged ceilings contains insulation or not. If the ceiling is on the top floor of the home, it means it’s insulated. Inner ceilings are usually uninsulated, but some homes have inner ceilings insulated for the sake of sound reduction purposes. Inner – building ceilings are less likely to have mold growth due to their uninsulated structures. Inner-ceilings are more comfortable to remediate if anyhow, mold growth does occur.

From the content mentioned above, you know that mold growth requires both moisture and food sources. Paper on the backside of the sheetrock is the best food source for mold growth. So, the moisture is only the controllable factor. It is time for uninsulated ceilings to show their advantages. The lack of insulation allows air to move on each side of sheetrock, which helps to dry it rapidly. Moreover, dehumidifiers and air movers, allow the air to remove moisture quickly.

Replace or repair?

The most noticeable thing in a ceiling remediation project is to find whether the ceiling requires replacement or repairing. If the water intrusion(roof leak) is the reason for mold growth, replacement is recommended. While on the other hand, if the mold growth is due to condensation, the ceiling can be repaired without being a replacement. 


Contact a professional mold remediation company if the replacement is warranted. Removing a ceiling can expose a large quantity of mold spore into the indoor air. So, containment is necessary.  If the mold is across a couple of square feet, this can be undertaken by a homeowner.


The conditions which help mold growth do not occur in properly designed, operated, installed, and maintained systems or homes. While on the other hand, in the environments where the water is allowed to accumulate on ceilings or walls, conditions can occur which promote mold growth in the ceiling or attic. You must have to protect your home from water intrusion and mold growth.