Aerial view of flat roofs of several brightly colored commercial buildings.

5 Signs It’s Time for Flat Roof Replacement

A flat roof is exactly what it sounds like: a roof that has very little slope to it. Usually, this style of roofing is used primarily in commercial applications, especially in the Pacific Northwest. You’ll find more residential flat roofs in parts of the country that are arid because one of the drawbacks to having a flat roof is that it can be difficult to find and repair leaks. With our consistent precipitation, no one wants to deal with that in their home.

The benefit of having a flat roof is that you can also use it for additional space. For instance, green roofs or eco-roofs are popular places to have small gardens where a roof is visible to inhabitants of the building or those around it. In urban places, such as downtown Portland, apartment buildings, colleges, and medical complexes are creating green spaces on the roofs visible to their students, patients, and occupants. This way, architects are also creating spaces for stormwater management, reducing the urban heat island effect—where cities have a higher ambient temperature due to so much concrete—and also creating spaces for pollinators such as bees and hummingbirds to live.

So, if you have a flat roof, how do you know when it’s time to perform some maintenance or replace it? Here are five signs it’s time for flat roof replacement:

1. Cracks in the Flashing

Anywhere there is a sharp bend on your roof—any 90-degree angle—there will be flashing, which seals water away from the interior of your building. Think of flashing as the seams of your roof. If your flashing is cracked and old, water has a natural pathway into your building. Needless to say, it can cause a lot of damage to the wooden joists under your roof, the support beams, and any insulation that might be there. You can bet that if you can find old and worn-out-looking flashing, other parts that you can’t see will need to be replaced too.

2. Blisters Forming

You’ll see this more commonly in a flat roof that has membrane roofing. Blisters or bubbles form when pockets of air or moisture are trapped between the layers of the membranes and can be exacerbated by regular foot traffic. Sometimes, they are a result of a crack in the seam, which then collects moisture or cold air from below.

If you catch a blister before it cracks, you can sometimes repair the roof instead of replacing it. However, if it’s a consistent problem, or the blisters or bubbles show up all at once all across the roof, it’s probably time to consider replacing it. Even if you’re able to repair one blister, there’s a good chance it will come back again and again.

3. Water Is Pooling

This is actually the biggest and most common problem with flat roofs, especially here in the Pacific Northwest. Since we live in a wet climate, you want to be sure that there are no places on your roof where water will “pond” or pool and have appropriate drainage. If you have a space where there is a consistent pool (and if your roof is fairly new), you can install additional roof drains or a tapered system. Of course, if you are maintaining an old roof rather than fixing a new one, you may have bigger problems. The faster you get the water off the roof, the better the chance you won’t spring a leak.

4. Building Materials That Hide Damage

You may think this is a good thing at first, but if the damage is hidden, it may not occur to you to repair or replace the roof until it’s too late. If you have a tar and gravel roof—which is becoming less and less popular for this reason—it may be difficult to actually find the damage, and even an experienced contractor may only have a 50-50 chance of finding the leak. If it’s time to replace the roof anyway, make sure the flat roof replacement material is something that is easy to work with and shows damage instead of hiding it.

There are many types of flat roof coverings, including asphalt, synthetic rubbers, liquid membranes, and glass-reinforced plastic. They all have advantages and disadvantages, so make sure you ask your highly experienced technicians at Interstate Roofing which one is right for your building and your budget.

5. Alligatoring

Have you ever seen the pattern in an alligator’s skin? You’ll see similar patterns in the cracks that can form in your roofing material. As the sun’s UV rays dry out the top layer of your roof, you’ll be able to see this kind of damage. Remember, while it’s frequently cloudy in our climate, some UV rays will still get through and slowly degrade your roofing material. Clouds only block some rays—not all of them. If you don’t handle this problem, these cracks can let in ice and water, and the heating and cooling cycles will make these cracks wider and lead to more and more problems.

But if you replace your roof, or if you apply a new coat to the roof when you first notice these patterns, you can say, “See you later, alligator!” to this particular problem. If you have noticed alligatoring in the past, or if you’ve recently replaced your flat roof, it’s good practice to inspect your roof every six months or so and after major storms, including ice and wind storms.

Flat roofing is one of our specialties at Interstate Roofing. We’ve worked on many large commercial buildings in Oregon and Washington, such as churches, office buildings, medical complexes, restaurants, warehouses, and multi-family structures. We were also awarded the Versico Gold Medal Quality Award for our work on the Timberline Wy-East Day Lodge. Having been in this business for over 30 years, it’s no wonder Interstate Roofing is the obvious choice for your roofing needs, whether it’s commercial or residential.