seams on flat roof

Roof Seams Coming Apart on Flat Roof: What to Do?

Greg PalyaSingle-Ply Membrane Roofing

Summary: If you notice even the slightest separation in your roof seams, you need to contact a roofing contractor immediately! If you ignore the problem, the separation will get worse, more water will saturate your insulation, and the repair (or possibly a complete roof replacement) will be more expensive than if you got the problem fixed immediately.

So, you went on your roof, and you noticed some of the roof seams are coming apart. I know you may think this is automatically going to be a bad thing.

I’m here to tell you, if you catch the lost adhesion fast enough, you can restore the roof, instead of completely replacing it.

In this article, you’ll learn:

  • What repair options you’ll have if your seams look pretty decent and your warranty is about to expire
  • What repair options you’ll have if your seams are breaking down and there’s some lost adhesion, but not much
  • What repair options you’ll have if your seams are completely blown apart
  • What causes roof seams to come apart?
  • What happens if you witness the seams coming apart and you ignore the problem?

And so you’re aware, West Roofing Systems has been in commercial roofing since 1979. We specialize in spray polyurethane foam and silicone roof coating systems.

We’ve restored every kind of roof system available, including single-ply membranes where the seams are coming apart.

Every article written at West Roofing Systems is produced in-house and is reviewed and approved by a spray foam and coating expert with more than 30 years of experience.

Let’s get started!

What repair options do you have if your roof seams are coming apart?

This all comes down to the current conditions of the roof. We’ll go through the repair options for a few different scenarios:

Scenario #1 – My seams look pretty decent, but my warranty is about to expire

Let’s say you’re on year 9 of a 10-warranty. The roofing seams are still pretty tight, but you want the roof to continue performing well in the future.

And you want the roof to perform well in the future at the lowest cost possible.

Since the roof is in good shape, you can restore the roof by installing a silicone roof coating system.

In short, a very thick, paint-like material (that’s engineered for commercial roofing elements) is installed over the entire roof, and you get a new 10-20-year warranty.

Here’s a video of a silicone roof system installation from start to finish:

Since you’ve been proactive in getting your roof repaired before your seams allow water into your roof system, this is the lowest cost option.

Cost always has plenty of variables such as roof size, length of warranty desired, etc. But in this case, you might be looking at spending around $2 – $4 per sq. ft. to keep your roof under a new 10-20-year warranty.

Scenario #2 – Seams are breaking down and there’s some lost adhesion, but not much

This comes down to how much of the roof’s insulation is saturated. Core samples and infrared surveys may be performed to determine the amount of saturation.

It’s not an exact number, but the magic number is 25%.

If less than 25% of the roof is saturated, it’s most likely beneficial to restore the roof with a silicone roof coating system.

If more than 25% of the roof is saturated, it’s most likely beneficial for long-term performance to do a complete tear-off and installation.

This is why it’s important to identify when your seams are coming apart so you can reduce the amount of water that enters the insulation.

Since there would be some tear-off no matter if you restore the roof, or do a complete tear-off, the cost is a wide spectrum.

The cost could be anywhere from $3-$4 per sq. ft. for restoration, and as high as $7-$9 per sq. ft. for a complete tear-off and another roof system installed.

Scenario #3 – Seams are completely blown apart

If the seams are in terrible shape or the amount of saturated insulation is more than 25%, the best option is to rip everything off and install a new roof system.

Although the price will probably be at least $5-$9 per sq. ft. this is a great opportunity to begin fresh.

Now you can choose which roofing system you’d like to install.

Here’s a blog post that highlights the pros and cons of all different commercial roofing systems.

One option you might not be aware of is a spray polyurethane foam roof.

It’s very similar in cost to any other roofing system but will reduce your energy costs from day 1, and it’s renewable.

Renewable means when the 10-20-year warranty expires, you don’t need to remove it. You make simple repairs and then add more coating onto the roof. The renewal usually costs 1/3 to ½ of the initial installation.

Because spray foam is renewable (and has the highest R-value per inch of thickness of any roofing system), it’s the roof system with the lowest lifetime cost.

What causes roof seams to come apart?

Four reasons roof seams come apart:

  1. Old age
  2. Adhesive breaks down from UV rays
  3. Water gets underneath, freezes, and expands
  4. Installed wrong on day #1

Let’s go through each of these in more detail.

Old Age

A typical warranty for a single-ply roof installed in 2021 is 15-20 years. 10 years ago, a typical warranty was only 10-15 years.

So, if your roof was installed around the years 2006-2011, your single-ply roof may be at the end of its lifecycle.

Seams on a roof expand and contract with weather fluctuations. After 10+ years, the stress has probably taken its toll.

Adhesive breaks down from UV rays

The seams on a roof can be attached using an adhesive. The UV rays from the sun can break down this adhesive.

The adhesive can become dry, eventually losing adhesion with the rubber sheets.

Water gets underneath, freezes, and expands

If water entry points exist, water will find a way to get underneath the membrane. When this happens in the winter, the water will freeze. When the frozen water thaws, it will create a larger opening than before.

This is because water expands when it freezes.

This is why it’s important to check your roof in the Fall to see if any of your roof seams are coming apart. Even if a little lost adhesion is present, the freezing and thawing will create a larger opening when it’s Spring.

Installed wrong on day #1

If your roof seams were heat-welded, perhaps the temperature was too hot which created pinholes. If the temperature wasn’t hot enough, the seams can appear together when really there’s a very weak connection.

If an adhesive was used, perhaps the adhesive was applied too thin. Or the contractor missed certain areas.

If the seams were put together using screws and plates (called mechanically-fastened), perhaps screws were inserted crooked, they missed the seam, or the screw wasn’t inserted down all the way. Screws and plates can easily be damaged with foot traffic as well.

Now that we know how seams can come apart, what happens if you notice (or don’t notice) the lost adhesion and no repairs are made?

What happens if you ignore roof seams coming apart?

If you ignore your roof seams coming apart, the separation is only going to expand, creating a more expensive repair.

Even if the seams are separated a teeny, tiny bit, this will allow water into your insulation.

If this is ignored for months where several thunderstorms have occurred, a large amount of water can get in the insulation.

Most roofs have open-cell insulation.

This means that water can get in the insulation and travel horizontally and vertically through it.

It would be the same if you continually dropped water from an eyedropper into the corner of a tissue.

Eventually, the entire tissue will be wet. The same can happen with roof insulation. A tiny entry point can saturate a large area.

And if this “saturated” area gets too large…the only repair option you’ll have is to completely rip off the entire roof, transport all the materials to a landfill, and install a brand-new roof system.


Compared to restoring your roof…yes.

What are your next steps?

Hopefully, after reading this article, the main point is clear.

If your roof seams are coming close to coming apart, are already apart, or are completely apart, it’s time to contact a commercial roofing contractor.

Any additional time this is on the backburner is only going to make the repair more expensive.

West Roofing Systems has been repairing, restoring, or completely removing commercial roofs with seam issues since 1979. Getting a contractor involved can provide you with repair options that fit your budget and future goals.

Here are some of our best articles on roof coating systems and spray polyurethane foam roofing:

download the silicone roof coating cheat sheet
About the Author

Greg Palya

Greg Palya is the Digital Content Manager of West Roofing Systems, Inc. He has a B.S. in Marketing from the University of Akron and an MBA in Marketing from Walsh University. When he's not trying to teach others about spray foam roofing and silicone roof coatings, you can find him on the basketball court or golf course.