Commercial, Mixed-Use and Strata Roof Maintenance in Vancouver, B.C.

What Causes Mold Growth In A House? (5+ Possible Reasons)

What Causes Mold Growth In A House? (5+ Possible Reasons)

As professional roofers, we are often called to remove mold from roof tiles or the attic. This brings me to the root of the problem. “What causes mold to grow in a house?”

Some of the reasons for mold growth could be, roof leaks, no proper ventilation, moisture, humidity, broken or faulty equipment, etc.

In this article, I have highlighted some of the main reasons for mold growth. Especially in your attic or anywhere in your roofing system. Moreover, there are some pro tips to prevent mold, and answers to a few common questions regarding mold growth.

6 Common Reasons for Mold Growth in your House.

#1 Moisture.

It’s no news that mold thrives in moisture. If you live near a water body, or generally have a humid climate. The air in and around your home may be moist.

Pro Tip: Maintain Humidity Levels.

Make sure there is less humidity in your home. A dehumidifier or an air conditioner will help you do this.

A meter to check humidity can also be helpful. Humidity keeps fluctuating throughout the day. So, make sure to control it accordingly.

#2 Leaky Roofs.

Roof leaks are one of the top 3 reasons for mold growth in the attic and on the roof. If your roof is old or worn out, it’s more prone to leaks. Cracked or broken shingles may also lead to leaks.

A leaky roof causes moisture build-up, making your home more susceptible to mold growth.

Pro Tip: Repair Leaks.

Fix the leaking roof immediately. This reduces the inflow of water. Which in turn means no moisture and no mold.

However, ignoring a roof leak may have more severe consequences than a mold infestation. Here are 9 Common Issues Causing Leaky Roofs. To help you spot a leak easily.

#3 Improper Ventilation. 

Mould needs a static and moist environment to grow. When air flows naturally throughout your home, such an ideal environment is not created.

Many times mold grows only in the attic, bathroom, under the sink or in the store room. As these places are mostly closed or unused. Therefore, there is no proper ventilation, compared to other rooms.

This traps moisture and facilitates the growth of mold.

Pro Tip: Ventilate Your Home Properly.

Let there be a free flow of air throughout the house. Install exhaust fans in your kitchen and bathroom to avoid moisture from trapping.

Keep all the windows open whenever possible. This will increase the natural flow of air.

#4 Incorrect Installations.

Roofing systems have several components, that need to be installed correctly. If any of these components are not precisely installed. Or even if the edges are not well sealed, water may find its way inside the house.

If these leaks go unnoticed for a while, a colony of molds may grow there.

Pro Tip: Hire A Professional. Avoid DIY Installations.

Get all your installations done by a professional, so you eliminate the risk of improper installation.

Also, scheduling regular roofing maintenance will benefit not only your roofing system but your entire house. Here are 5 Reasons To Book Regular Roofing Maintenance.

#5 Damp Basement and Foundation.

It’s almost impossible to have large windows in the basement. Hence, the scope for natural ventilation is low. The air in the basement is usually stagnant and a bit moist.

Moreover, the basement is inside the ground. So, the chances of moisture seeping in from the ground are more.

If your basement is not waterproofed, then water from the above structure and the surrounding will give rise to leaks. Over time the dampness will cause mold growth on the walls and the stored things.

Sometimes the yard is not sloped enough, so the water doesn’t flow away. Rather it puddles around the home. And slowly, seeps into the basement and the foundation of the house. This leads to Toxic molds growing on wet walls.

Pro Tip:  Direct Water Away From The House. Find A Way To Keep Your Basement Ventilated.

Do not let the water puddle around your house. It’s ideal to elevate your home from the surrounding. Make sure your drainage system is functioning well.

#6 Faulty Equipment.

Washing machines, air conditioners, refrigerators, dishwashers, and water heaters, are some of the common equipment present in everyone’s house. If these machines are faulty, overused or old, the condensed water may leak, and cause mold growth.

Pro Tip: Maintain Your Equipment.

Timely servicing and replacement of such electronic products is the only way out of this.

Some Measures To Prevent Mold Growth.

  • Keep Your Place Dry.

Do not let spilled water or any liquid stay on your floor or your furniture. Especially, if you have wooden flooring, clean the liquid immediately. If you have toddlers or kids in your home, this may be a common occurrence.

Keeping your place dry is an easy way to prevent moisture and mold growth.

  • Equip Your Home With Mold-Resistant Products.

Use mould-resistant products like mould-resistant drywall. Add mold inhibitors to paint before painting your house.

Use mold-killing products to clean your bathroom, attic, store room or any place in close contact with water.

  • Clean And Disinfect Surfaces.

If you plan on clearing the mold yourself. Scrub the moldy surfaces with a stiff brush, hot water, and detergent that has no ammonia. Rinse with clean water afterwards and dry the surface.

After cleaning, disinfect the surface with bleach and water. (Never mix bleach with ammonia as it produces toxic fumes.)


Does mold growth affect our health?

Yes! Exposing yourself to mold for an extended period is harmful. It may cause allergies. Sneezing, watery eyes, itching, coughing, runny nose, breathing difficulty, wheezing, and fatigue are some common symptoms. People who are sensitive and have breathing problems. Like asthma or chronic lung diseases are more prone to severe allergic reactions.

Can you paint over the mold?

Yes! You can paint over the mold to cover the dark patches. However, painting won’t kill it. Using mold-resistant paint will only prevent its growth, but not terminate it completely. It will always reappear once the paint fades off.

Is there a spray that kills mold growth?

Yes! There are sprays available in the market to kill molds. These sprays get rid of the stains, as well as stop mold infestations in the future.

Does black mold have to be removed professionally?

Yes! Black mold is more harmful than other types of molds. Hence, calling a professional is suggested.


Indoor mold growth is a health hazard. In this article, I have summed up all the possible reasons for mold growth and the solutions to it. However, hiring a professional to handle such tasks is the best option. If you are in search of a reliable and experienced roofing company, call us anytime!

Leak Stop is a one-stop destination to meet your roofing-related requirements. We offer roof repair, replacement, maintenance, and inspection services all over GVRD (Greater Vancouver Regional District).

We offer a free inspection to first-time clients. Connect with us TODAY at 1 866 777 0084 for immediate assistance!


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