How Long Does It Take For Mold To Grow From A Leaking Roof?

by Allied / Tuesday, 15 June 2021 / Published in Mold Remediation

It’s shocking to realize how quickly mold can grow when there is an abundant and constant source of moisture nearby! And if you have a leaky roof, a mold problem can progress from “non-existent” to “total disaster” in as little as a day, and eventually require costly repair. 

How fast does mold grow?

Just how quickly does mold grow in homes with leaky roofs? The actual amount of time varies depending on various factors, including:

  • amount of moisture 
  • frequency of exposure to moisture 
  • temperature
  • humidity level
  • type of surface
  • building material

Apart from the amount of moisture and frequency of exposure, temperature and humidity levels are the most significant factors contributing to mold growth in the average home. 

If the conditions are just right‒that is, if the temperature and humidity levels are optimal‒mold spores can germinate and grow within 24 to 48 hours. In some cases, you can see signs of a full-blown infestation in about a couple of weeks or so! Alarming, isn’t it? 

Mold spores start the colonization process in as little as three to 12 days. By 18 to 21 days, your mold problem will probably become quite apparent. The longer the issue remains unresolved, the greater the chance of mold developing and spreading to the other parts of your home. 

How quickly does mold spread?

Within a few hours, what seems like insignificant mold growth will begin to spread to the adjacent areas. Mold spores are surprisingly hardy and will thrive on most organic material with even just a little moisture. 

Once the spores find favorable conditions to grow‒typically on porous material‒they will send out roots and begin feeding off anything it deems a suitable food source. 

After a few hours, the spread should be well underway. The spores will eventually damage the underlying structure of the material in which they take root. Over time, the spores float up into the air and spread throughout the home. When they find other areas with favorable conditions, the process begins over again. 

How water damage relates to mold growth 

One of the most disturbing things about mold growth is how little moisture is necessary to cause a problem. Even seemingly insignificant cases such as a leaky roof that causes only a little water to enter can trigger a full-blown mold infestation. 

Keep in mind that mold spores can be found almost everywhere. When they are exposed to the right conditions‒that is, with sufficient food and moisture‒they will begin to grow and spread surprisingly quickly. 

Most homes have plenty of porous organic surfaces that serve as ideal breeding grounds for mold. Drywall, paper, and even paint and insulation could all be potential ground-zero for mold to take root and spread. 

How to prevent mold from spreading after water exposure 

The first thing you should do after your roof springs a leak is to eliminate the source of moisture. This typically means fixing the leak as soon as possible. 

But what about the moisture that is already in the house? 

You will have to act equally quickly to dry all the areas that have been exposed to water. Pay particular attention to nooks and crannies and underneath furniture and large plans appliances. Because these areas tend to retain moisture long after the initial exposure, they provide plenty of opportunities for mold to grow and spread. 

How much time do you have to dry the premises? Considering the growth cycle of mold spores, it would be best to dry all exposed surfaces within 48 hours. At the very least, you should complete a thorough drying and cleanup job within 72 hours after the initial leak. This will help ensure that existing mold spores will be cleared out before they have a chance to propagate. 


Mold growth can be a serious problem, especially if you have moisture-related issues in your home. If you have a leaky roof, it’s only a matter of time before you see signs of mold taking root. 

Fixing the source of moisture is the first step toward solving your mold problem. Try to get your leaky roof repaired as quickly as possible. This will prevent the problem from worsening and save you the cost of mold remediation and home restoration.

For mold restoration in around Kalispell, Montana get in touch with our team for a quote on getting your home back in shape!