Moisture is one of the most common and damaging elements that can affect a commercial roof. Roofs are continuously exposed to various environmental factors, and moisture can infiltrate through cracks, seams, or other vulnerabilities, leading to a host of problems. Whether your building is in a region that experiences severe rainstorms or heavy snow, understanding how moisture can affect your structure is essential.

This article will discuss eight specific ways that moisture can damage a commercial roof, impacting its structural integrity, longevity, and overall performance.

Water Pooling and Standing Water: Water pooling, often seen in low-slope or flat roof designs, occurs when water does not drain off the roof effectively. This can be caused by clogged drains, poor drainage systems, or improper slope installation. When water accumulates in low areas of the roof, it exerts pressure on the roofing materials, leading to the degradation of the roof’s surface. Standing water can weaken roofing membranes, resulting in cracks, blisters, or even punctures. Over time, this can cause the roof to fail and may lead to water infiltration into the building. (Read more about how roof coatings can prevent against water damage.)
Roof Membrane Deterioration: Moisture can accelerate the deterioration of roofing materials, especially when water is trapped underneath the membrane. Roofing systems like EPDM, TPO, or modified bitumen are designed to withstand exposure to water, but prolonged moisture exposure can lead to the breakdown of these materials. As the membrane deteriorates, it becomes more susceptible to punctures and tears. This reduces the overall protective barrier of the roof, increasing the risk of leaks and water damage inside the building.
Corrosion of Metal Components: Many commercial roofs feature metal components, such as flashing, vents, or gutters. Moisture can promote corrosion of these metal parts, weakening their ability to protect the roof from water penetration. Corroded metal components can lead to the loosening of seams, creating openings where water can enter. In some cases, water may seep into the building, leading to expensive repairs and mold growth.
Mold and Mildew Growth: Moisture, when allowed to linger on a roof or in its underlying layers, creates an ideal environment for mold and mildew to thrive. These fungi can grow in areas where water has been trapped for extended periods, such as in roofing insulation, behind flashing, or in roofing materials. The presence of mold can weaken the roof’s structure and cause health problems for the building’s occupants. In addition to health risks, mold growth can lead to foul odors, staining, and further deterioration of the roof materials.
Roof Insulation Damage: Moisture infiltration can compromise the insulation layer of a commercial roof. Insulation, often made from fiberglass, foam, or cellulose, becomes less effective when it gets wet. Waterlogged insulation loses its thermal resistance properties, which can lead to higher energy costs as heating or cooling systems work harder to maintain comfortable indoor temperatures. Additionally, wet insulation can add weight to the roof structure, increasing the risk of structural failure, especially if the moisture is not addressed in a timely manner.
Freeze-Thaw Cycles: In colder climates, moisture on a commercial roof can lead to freeze-thaw cycles, which can be extremely damaging. When water seeps into cracks or gaps in the roofing materials, it can freeze during cold weather. As the water freezes, it expands, putting pressure on the roofing materials and causing them to crack further. When temperatures rise and the ice thaws, the water contracts, leaving behind cracks or holes that can allow even more water to penetrate. Repeated freeze-thaw cycles can cause progressive damage to the roof, leading to costly repairs or early roof replacement. (Read more about roofing damage in extreme cold temperatures.)
Structural Damage and Weakening: When moisture infiltrates the roof and reaches the underlying structure, such as the deck or rafters, it can weaken the materials. This is particularly concerning in wooden structures, which can rot and decay when exposed to moisture over time. Moisture that gets into the building’s structure can lead to warping, sagging, or even total collapse in extreme cases. Water may also seep through cracks and affect the building’s interior, resulting in ceiling stains, compromised electrical systems, and water damage to interior spaces.
Leaks and Water Intrusion: Perhaps the most obvious issue caused by moisture is roof leaks. When moisture infiltrates through compromised roofing materials, it can cause water to enter the building’s interior. Leaks can damage ceilings, walls, electrical systems, equipment, inventory, and other critical assets inside the commercial space. Water intrusion can lead to extensive repair costs, downtime for the business, and even insurance claims. In the worst-case scenario, it could even force businesses to relocate temporarily or permanently.

By staying proactive and addressing moisture-related problems early, businesses can extend the life of their roof, avoid costly repairs, and prevent business disruption. One of the best measures you can take to protect your roof from water damage – whether proactively or as a repair – is to apply roof coatings. Unicoat Industrial Roofing has applied over 4 million gallons of roof coatings across the country – call today to learn more.