3 Common Flat Roof Problems & How to Avoid Them

Flat Roof Construction

Did you know that a roof is considered "flat" if it has a pitch of 10 degrees or less? This means, if you have a very minor pitch to your roof, you may have a flat roof without even realizing it! Flat roofs are used in both residential and commercial settings, and they offer many benefits. For example, flat roofs are very accessible and often are easier to maintain and clean. This is especially attractive to residential homeowners who aren't experienced in moving around on a pitched roof.

Flat roofs are typically made from:

  • Foam (polyurethane)
  • Modified bitumen (asphalt)
  • Tar and gravel (built-up roofing or BUR)

With proper care and maintenance, a flat roof will last for around 15 years.

Problem #1: Leaks

Water and moisture can be extremely destructive. Flat roofs do not shed water as readily as pitched roofs. Consequently, leaks are not uncommon. Even when properly installed and sealed, if the water is left to sit on a roof, it will find a way inside. In addition to leaks inside your home, leaks can also degrade your roof's materials and lead to mold and mildew growth.

Similarly, pooling water is another concern for flat roofs. Over time, materials will shift, and parts of the roof may dip or even start to sag, allowing water to pool up or pond on the roof. This not only leads to leaks but puts a lot of stress on your roof.

How to Avoid Leaks in Your Flat Roof

To combat leaks on a flat roof, you want to make sure that your roof and the roof's drainage system is well maintained. Make sure to have your roof inspected annually, and if you notice any signs of a leak, call out a professional roofer as soon as possible. Similarly, damaged flashing and poor seals around roof installations (such as skylights) can also lead to leaks, and these should be inspected regularly and repaired when necessary.

If water is pooling on your roof, you should schedule an inspection with a roofer to assess how serious the problem is. As your roof expands and contracts with changing temperatures or shifts as your house settles, it will not remain perfectly level. Small dips in your roof are not necessarily a cause for concern, but any pooling water should be drained as quickly as possible. After heavy rains, it is worth checking your roof for damage and evidence of pooling.

Problem #2: Debris Buildup

Just as water doesn't drain from a flat roof as easily as from a pitched roof, flat roofs are more prone to debris buildup. With a pitched roof, leaves, pine needles, branches, and other objects are more likely to slide off. On a flat roof, they are more likely to sit there. Debris buildup can degrade your roofing materials, put undue stress on your roof's structure, and can lead to water dams and leaking. It can also clog drains and vents.

How to Reduce Debris Buildup on Your Flat Roof

Flat roofs need to be cleared of debris regularly. This can be done with a broom or a blower. You may also wish to pressure wash your roof to help remove more stubborn debris. In addition to performing annual maintenance, you should check your roof seasonally, especially during the fall when leaves and branches are more likely to fall on your roof. Set a reminder on your calendar to inspect your roof for debris buildup quarterly.

Problem #3: Blistering

Flat roofs are comprised of several layers of materials. When the roof is installed, these layers are adhered together. Roofs become at risk for blistering when the adhesion between the layers degrades or is compromised. If moisture or air makes its way in between the layers, you will see raised areas (or blisters) on the roof's surface. Blistering is a common issue in all flat roof types and can affect both commercial and residential roofs.

Blistering can be caused by many issues, including pooling water on the roof, poor drainage, debris buildup, poor roof ventilation, or mistakes made during installation. The occasional small blister is not necessarily a sign that you have to replace your roof. However, if you see blistering, you should keep an eye on it and schedule an inspection with a professional roofer.

How to Deal with Roof Blistering

The best way to prevent blistering on your flat roof is to keep the roof well-maintained and free of debris. If you notice any repair issues, such as pooling water, you should have the problem repaired as quickly as possible. You should also make sure that your roof is properly sealed to help prevent excess moisture buildup. While you can do a lot to stave off blisters, if you have a flat roof, you will likely experience them at some point.

If your roof is already experiencing blistering, you have a couple of options. Some blisters that result from air between the roof layers can be left alone if the top layer is still watertight. However, if your blister breaks or results from moisture seeping between the layers, you will need to have them professionally repaired. Many roofing systems come with a warranty, and repairs may be covered. If blistering is severe or your roof is nearing the end of its life cycle, you may wish to replace the roof. Before making a decision, speak with a professional roofer for guidance.