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Will A Roof Leak Cause Mould?

It’s so easy to procrastinate when it comes to household issues. However, a roof leak should be a top priority on your maintenance to-do list. 

Roofing leaks can develop for a number of reasons: improper roof installation, wind or storm damage, and lack of maintenance.

Most homeowners think a leaky roof is just a structural problem, but it can actually cause many health and safety risks. 

Constant water intrusion will eventually work down from the attic area to the very foundation of the house, causing plenty of costly damage on the way. It’s so important you don’t ignore even the smallest leak!? 

Here are some of the less-obvious ways a roof leak can damage your home.

How Long Does a Roof Last?

A roof replacement is a major expense, so it’s a given that most homeowners want to prolong a roof’s life span. If you experience water infiltration during a rainstorm, you may wonder whether it’s time to replace your roof shingles. 

Some roofs wear down unevenly due to sun damage, exposure to natural elements like wind, or due to improper installation. So you may need to replace part or all of your roof system before the end of its typical lifespan, which is typically between 20 to 30 years.  

The average cost of a roof replacement is $7,200, but this amount can vary significantly. The first step for dealing with roof leaks and mould is to determine the cause of the leak and then have it repaired.

Causes of Roof Leaks

Your roof may be damaged by a number of factors like hail, high winds, torrential rains, heavy snowfall, and ice dams. The roofing materials may be incorrect or improperly installed, or they may wear down with time. 

Whatever the reason is, your damaged roof will inevitably result in a leak. The causes of roof leaks vary, but the most common that can lead to slow water damage include:

  • Broken or missing shingles
  • Improperly installed or damaged flashing
  • Incorrect roofing materials
  • Ice dams

Shingles become damaged or even get blown away in strong storms. However, it’s not always easy to see if a shingle is damaged.

Sometimes the only indication of its poor condition is after water damage has already happened.  

But often, a damaged or missing shingle is obvious, especially if you notice a few of them around the backyard after a storm. 

Improperly installed or damaged flashing, the metal installed around the chimney, dormer windows, skylights, and any vent pipe, can allow water and moisture into the home, causing mould to develop.

Certain roofing materials are designed specifically for certain types of roofs. For example, a roof with a steepness that’s less than 3:12 requires materials designed specifically for a flat roof.

If your roof was not constructed with the proper fitting materials, leaks could happen. Also, If the valleys (the places where two roof planes come together) are not sealed together well, rainwater can get through them as it runs down the roof.

Improper installation and/or decayed insulation along the skylights’ edges will allow water to leak into the home;

Ice dams can also cause roof leaks by preventing water from melting ice from draining off the roof. So the water collects behind the dam and can leak into the home, causing damage to walls, ceilings, insulation, and other areas.”

Signs of Roof Leaks

In order to identify potential problems from getting worse, you need to know what to look for when inspecting your property for damage. 

Even though properly constructed roofs can last for decades, you are strongly recommended to inspect your roof once or twice a year, as well as after every major storm. Otherwise, minor roof leaks may go unnoticed and result in severe property deterioration.

Common signs of roof leaks include:

  • Watermarks on ceilings and/or walls
  • Discoloured areas on ceilings and/or walls
  • Darkening of ceiling paint
  • Peeling paint around skylights or dormer windows
  • Peeling, cracked, bubbled plaster
  • Mould growing around the chimney
  • Wood rot in the attic, around skylights or dormer windows
  • Discoloured wood in the rafters (may appear like a reddish, rusty colour)
  • Crumbling, deteriorating drywall
  • Musty or mildew smells in the attic
  • Mould on attic insulation
  • Water seepage during heaving rainstorms or during a snowmelt

Even if you notice some of the above tell-tale signs of a roof leak, it may be difficult to locate the problem. Water can travel along roof panels or lumber in the attic before dripping onto the insulation and leaving any visible evidence of its presence. 

If you cannot find the leak, it may be a good idea to have your roof professionally inspected, as timely roof leak detection will help you prevent severe structural damage and hazardous mould issues.

Roof Leak Detection

When your roof has a leak that causes ceiling mould, the mould will usually be black. However, not every black mark is mould. Cigarette smoke can also cause black streaks across the top of your ceiling.

However, as you look closer at the black marks, also look for mould identifying features. On top of being black, ceiling mould from a roof leak usually has a fungal structure.

You may also think you have a roof leak when humidity and moisture levels are too high. If your house is getting too humid and moist during the day, mould might begin to form on the inside.

However, mould that comes from moisture and humidity will typically be worse towards the perimeter of the room’s floor, not the ceiling. When the mould is primarily forming on the ceiling, it’s likely from a leak in your roofing structure.

What does attic mould growth from a roof leak typically look like?

Roof leaks cause two types of mould growth: systemic or limited growth. Systemic growth occurs when the roof leak causes enough moisture to build up in the attic and cause mould growth throughout the entire area. 

In this case, the moisture buildup is indirect (the roof leak only affects a small area, but the dampness in the air causes condensation throughout).

Limited growth occurs when an attic has sufficient ventilation to reduce the effects of the additional moisture caused by the roof leak. In such cases, the mould remediation efforts can focus solely on the area surrounding the leak.

In the longer term, mould and mildew growth can really cause serious damage. Mould can spread throughout the home’s structure, to the HVAC system and then to the rest of the house through the vents where it can invade carpets, furniture, and even clothing.

Black mould is the most common type resulting from chronic water intrusion. Toxic black mould growth is rare, but even non-toxic black mould attacks wood framing, ceiling tiles, and wall and floor coverings. Mould is difficult to get rid of, and it is rather costly. 

How Long Does It Take Before Mould Sets In?

According to the latest scientific research, mould can begin to form in as little as 24 to 48 hours following moisture accumulation. That’s because mould spores are ubiquitous, and it doesn’t take long for them to find and settle in water.

Health Dangers of Mould Caused by Roof Leaks

Mould and mildew can lead to serious health issues, especially for those with high sensitivity, including nasal congestion, rhinitis, inflammations, and asthma. 

Mould spores continue to reproduce and will lead to allergic reactions, asthmatic symptoms, and even more serious health problems.

Not only is mould unsightly, but it also jeopardises the health of your entire household. The word mould is a nonscientific way to describe different types of fungi. Additionally, mould comes in different colours such as black, brown, or pink.

Certain moulds smell bad, and other moulds have a fuzzy texture. For mould to be active, there has to be moisture to feed it. Even a small leak in your roof is enough to give mould the moisture it needs to thrive.

Once the mould is actively growing in your roof, your house is more likely to have the type of dust mites and bacteria found in a mouldy environment. As a result, everyone in your household may start to experience mould-related sicknesses.

For example, mouldy environments can make it easier to develop respiratory problems. Also, healthy household members could suddenly start to experience shortness of breath, wheezing, or coughing.

Other health concerns include the heightened likelihood of infection. Finally, if anyone in your house suffers from allergies or asthma, mould can make those conditions worse.

Roof Maintenance Mistakes That Cause Leaks

If you suspect there’s a leak in your roof, it could be the result of several roof maintenance mistakes. To begin with, you’ll want to check the condition of your roofing material.

If you have a roof with shingles, do the shingles look old and deteriorated? When shingles age, they lose their ability to insulate your home and keep out the water properly.

Simply replacing the old shingles with new ones could solve everything. If it’s not the entire roof that has bad shingles, and it’s only a few small spots, you can look into shingle repair.

When new shingles are giving you issues, it could be because the new shingles are lying on top of old shingles. Covering up old shingles with new ones can cause major problems such as roof leak mould, or other roofing issues.

To fix the problem, you’ll have to hire someone to completely strip off all of the shingles and lay down new ones. If your roofing material isn’t causing your leaks, your moisture protection might be to blame.

It’s possible that the last person to work on your roof used low-quality moisture protection. By upgrading to high-quality moisture protection, you help prevent leaks for the long term.

Another issue that causes roof mould is failing to have proper ventilation. When your home’s roof doesn’t have the proper ventilation, heat and moisture can buildup and cause mould.

Finally, the location of the nails in your roof also affect the roof’s integrity. If a roofer put nails in the wrong areas, the nails will corrode and leave holes in your roof.

Roof Leaks and Insurance

You may be wondering if homeowner’s insurance covers roof leaks? It depends on the specific type of policy and the cause of the leak. What matters is how quickly you noticed the problem and what subsequent actions you took. 

Most policies cover damage from leaks as long as you acted promptly upon noticing the damage. Your claim may not be accepted, for example, if you ignore a wet spot on the ceiling for a couple of months and only report the problem only after it gets worse. The damage must be “sudden and accidental” in order to be covered by insurance. 

Generally, home insurance doesn’t cover damage from normal wear and tear or from neglected maintenance. According to most insurance policies, failure to detect a roof leak constitutes negligence. 

It may take mould weeks or months to become visible on a typical interior surface, so the leak that has caused it is unlikely to be sudden and new. This discovery time-lapse will be considered negligence on your part. The idea is that you are expected to conduct detailed home inspections on a regular basis.

Minor roof leaks can be very difficult to detect, especially if you have no reason to suspect a problem. The sudden appearance of mould in the attic may be your first indication that something is wrong. 

In this case, your insurance claim will probably be accepted, provided that you report the damage as soon as it becomes apparent and take immediate action to stop the leak and prevent further harm.

Have in mind, though, that even if your water damage claim is accepted, the cost for repairing the leak won’t be covered, unless the roof was damaged by hail or a fallen tree.

The discolouration on the ceiling is primarily due to staining rather than mould growth. Mould growth may be present on the top side of the sheetrock (in the attic). However, the growth is likely minor, and due to the stack effect, it would not impact the indoor air quality. 

The removal of the ceiling is not always necessary. In this case, you would simply paint it over with a stain-blocking primer. An oil-based one works best.

Immediately address the source of the leak, and try to prevent any more water from accumulating. Dry all damp surfaces with a wet/dry vacuum and a dehumidifier. 

For major leaks, get in touch with a qualified contractor right away. If mould does begin to form, contact a mould specialist.

If leaks continue to spread through your home, it will lead to structural damage in the foundation. This will decrease the property value of your home and lead to expensive out of pocket repairs. If you have a roof leak, it is recommended that you don’t delay and make it a priority to contact one of our roof repair specialists at Top Glaze today. 


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