10 Common Issues Faced With Flat Roofs

When it comes to flat roofs, be they commercial property or more modern homes, you know that it often requires more work than other standard roof types. Typically, flat roofs offer many advantages, such as being cost-effective, easily accessible, relatively easy to install, and even energy efficient in some cases. Flat roofs also provide an ideal location for various building components such as HVAC units, solar panels, and communication equipment.

Even with these benefits, flat roofs typically require inspections and subsequent maintenance to ensure they are kept in good shape and functioning correctly for your home or business. The tricky thing about dealing with a flat roof is knowing whether you need some simple repairs or a complete replacement to get it back in shape.

To help better understand what you can expect with a flat roof, we have compiled a list of 10 common issues faced with flat roofs.

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    water and debris on flat roof

    1. Exposure

    Exposure is essentially the root of all flat roof problems when dealing with the extreme weather variances experienced in Edmonton and the surrounding area. Your home or building’s roof is exposed to the sun, snow and other elements, so damage is inevitable. No roofing material can last forever, regardless of how durable the roofing material is.

    Some other types of exposure that can be of concern are:

    • Lightning strikes
    • Extreme cold
    • Hail
    • Wind damage or wind-driven debris.
    • Oil damage in restaurants
    • Other outside pollutants and chemicals.

    2. Leaks and Moisture

    Leaks and moisture build-up are the most common problems with flat roofs, but they can be dealt with effectively if you stay on top of it. Like any roof, a flat roof will develop leaks over time, but the water doesn’t have anywhere to go but straight down. When leaks appear, moisture can find its way into the roof structure, leading to mould and fungus. The only way to deal with this is to ensure that you have regular roof inspections and that maintenance gets scheduled every time you find an issue.


    3. Ponding Water

    As is easily understood, flat roofs don’t always provide the proper drainage for water to escape. Most flat roofs get constructed with a slight slope to allow for the necessary drainage, but the lack of any natural slope can sometimes create issues. Water can collect and generate standing pools on the roof without a proper slope or pitch. The weight of the pooled water can eventually cause the roof to sag and potentially become a leak.

    4. Tears, Splits and Punctures

    With some of the extreme weather that we experience in Edmonton, flat roofs are prone to punctures or tears from storm damage. The potential for damage is why commercial roof inspections are essential after any significant weather event. Any foot traffic on the roof can also cause punctures, but restoration systems incorporating proper walk paths can avoid this issue.

    5. Structural Movement

    The extreme heat and cold variances experienced in Edmonton can play havoc on a flat roof. Structural or thermal movement is the natural expansion and contraction of a building’s envelope based on temperature. Though a natural occurrence, it can lead to movement in the roofing and the entire building structure.

    Whether cranking up the heat during our freezing winters or blasting the air conditioning during our hot summers, there always tends to be a significant difference between indoor and outdoor temperatures.   The temperature variance can lead to thermal movement, especially in commercial buildings. The excess movement experienced causes flat roof membranes to crack and split around penetrations, seams, and other flashing details.

    6. Debris Build-up

    Debris on a roof can be loose material such as leaves, tree limbs or branches, dirt/mud, or even trash from human presence. Over time, all roofs will collect a small amount of debris due to natural wear and tear and exposure to the elements. Still, too much debris build-up can clog drains and cause excessive damage that cannot be repaired, especially on flat roofs lacking a natural drainage slope.

    To ensure a flat roof drains correctly, you can remove the debris by hand, leaf-blowing, or pressure-washing.

    7. Biological Growth

    Biological growth can form in any standing body of water. For example, a swimming pool left unattended with no water circulation will soon fill with algae. When pooling water on a flat roof sits for long periods, vegetation and algae can form. As this biological material builds up, a roof will become less reflective and ultimately impact interior and exterior temperatures. Regular inspection and cleaning are necessary for roofs at risk of pooling water to reduce the risk of growth.

    8. Blistering or Alligatoring

    Blistering and alligatoring are two common problems among membrane roofing systems.

    Alligatoring is when the asphalt used to build your flat roof has aged and has lost its elasticity, causing it to crack and bubble. This cracking and bubbling look like the skin of an alligator, thus the name. When this happens, your asphalt flat roof has deteriorated past the point of repair and will need to get replaced.

    Blistering is a different phenomenon where bubbles form underneath the roof’s membrane. Blistering sometimes results in cracks, but unlike alligatoring, the cracks caused by blisters usually follow the blister’s length rather than forming a pattern.

    9. Shrinkage

    Shrinkage occurs on flat roofs made from membranes, such as SBS or Modified Bitumen (Styrene Butadiene Styrene). It causes seams to delaminate and pull apart, eventually creating openings on the roof’s surface.

    Though the durability of SBS makes it a popular choice in the construction of flat roofs, all SBS roofs can eventually experience some shrinkage.

    10. Neglecting Maintenance

    Perhaps the single most significant cause of premature roof failure is neglecting to perform routine maintenance. With a regular maintenance plan and commercial roof inspection, the above-mentioned flat roof issues can be preventable.  


    If you have questions about the condition of your flat roof, or if you think it’s time to get it inspected, call the experts at MD Roofing & Sheet Metal. With over 25 years of experience in Edmonton roofing, we’ll be able to tell you exactly what’s going on and fix it quickly. Contact us at (780) 439-7663 for your free quote.