Commercial Roofing Mistakes That Lead To Leaks

Commercial building roof depicting commercial roofing mistakes

When it comes to commercial roofing, it is common to hear complaints about leaking in flat roofing systems.

However, commercial building owners and managers don’t have to live in fear that the roof will inevitably leak. It is all about maintaining a relationship with a reputable roofing company.

Here are the top reasons why:

  • 98% of all roof repairs that are needed happen in or around roofing penetrations or perimeters.
  • Anything that is protruding up from your roof and creates a break in the membrane.
  • Curbs, drains, vent stacks, antennae bases, skylights, plumbing stacks, penthouses, electrical, and copper lines all present a challenge in terms of correct installation of a flat roofing system and in maintaining that system without leaking. If these aren’t handled correctly, they are more prone to leaking.

Examples of Commercial Roofing Mistakes

Here are some of the ways a contractor can make a mistake that leads to leaks:

  1. Poking a hole and then putting some sort of sealant around it. This is not attractive, and it isn’t water-tight.
  2. Using non-compatible roofing materials together, like plastic cement on single-ply membranes. Trust us; this isn’t good.
  3. Covering electrical cords or conduits as they will need to be accessed eventually.
  4. Clogging drains that lead to ponding on the roof.
  5. Over spraying with coating – that could lead to insurance liability.

Correctly Sealing Penetrations

There is no way to avoid flat roofing penetrations. Most flat roofs are used for any number of utility items. However, they do also have to keep out the elements from the rest of the building.

In addition, the trick is to seal each penetration the right way. There are several methods:

  1. A three-coursing approach: one layer of sealant, one layer of fabric, followed by one layer of sealant. After that, the right approach is to sugar-in matching granules with the main surface of the roof. This makes it look nice, like it blends in, and also protects the vulnerable spot.
  2. There are other types of sealant  that can be used on metal, on concrete, and wood, as well as any number of flat-roofing materials. This kind of sealant works well for when flat roofing material meets up with gutters, edge metal, or for details that could end up leaking if left unsealed or are sealed improperly.
  3. For difficult-to-seal areas: for areas full of irregular shapes, there is a pourable sealant that needs no fabric or granules, and it bonds with asphalt for places where flashing is impossible to use.


For commercial roofing, as with any roofing system, the vulnerable points on the roof are always those where a joint occurs. When we use asphalt shingles on a sloped roof, we use flashing and tie it correctly with the rest of the roofing material.

In contrast, on a low slope or flat roof, when there are many irregular penetrations in the material, it is always important to make sure those irregular jointures are sealed correctly. Thankfully, that is made possible by a variety of sealant products that ensure a water-tight bond.

It is critical that you use a reputable commercial roofing company who can stand by their work and will fix any leak that crops up. If your building is located in Southeast Michigan, please give us a call.

Call today!


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