What Exactly is a Self-Flashing Roof, and What are The Advantages?

When a roof’s top layer doesn’t require fasteners, adhesives, or rocks to have it attached, it is said to be a self-flashing roof.

Only two examples exist of a self-flashing roof.

One is Spray Polyurethane foam roofing. This is a fluid-applied type of roofing and instantly grows to 30 times its original size. The foam will get harder and adhere to the surface below.

The second is also a fluid-applied type of roofing and it is an Elastomeric roof coating system (silicone, urethane, or acrylic). These coatings are made of extremely thick paint and are designed to endure all kinds of weather conditions. The coating can be sprayed on or rolled out and it will stick to the below surface.

Why is this important and what advantages can self-flashing roofs offer?
This post will discuss the issues that involve fastening, adhesive-related problems, general advantages, and disadvantages of both, as well as the benefits of a self-flashing roof.

You may want to note that a commercial roofing specialist, with more than 30 years’ experience, has vetted and edited every article written by Stanley Roofing Company. Stanley Roofing Company has been a roofing contractor since 1979.

Let’s get started with the details!

Metal, TPO, and EPDM roofing membranes must be fastened to the insulation or roof deck below.

Problem no. 1: Fasteners may back out
In response to changes in temperature and general weather conditions, a roof will expand and contract. Hot summer days can see your roof’s temperature soar to around 180 degrees. In the evening temperatures drop and the roof’s temperature can now hover at around 60 degrees, all in the same day. This means in one day your roof may have to deal with a temperature difference of 120 degrees, which is quite significant.

Your roof responds to the weather with expansion and contraction daily, year in and year out. With the passage of time, fasteners can start to shift and eventually back-out. When this happens, a weak point is created, and water now has a perfect entry point.

Problem no. 2: Thermal bridging can be caused by fasteners
Fasteners are installed in such a way that they go through the insulation layer as well as through the top roofing layer. This then creates a space for air flow, which is counterproductive.


Problem no. 1: Sealing of penetrations
When a membrane needs to be secured to a roof penetration, roofing contractors make use of adhesives. As an example, the installation of a HVAC system will penetrate a portion of rolled out TPO.

With the installation of a single-ply roofing system, special cutting, termination metal and sealants will be required to seal this penetration. This would apply to all kinds of roof penetrations, like drains, HVAC systems, skylights, or pipelines.

Problem no. 2: It is expensive
One of the disadvantages is that adhesives are very expensive. When you are trying to limit the cost of your roofing project, it is not always feasible to make use of adhesives.

Problem no. 3: Limited lifespan
Adhesives have a limited lifespan. As mentioned previously, the roof needs to cope with years of continued expansion and contraction, which can cause adhesives to lose their effectiveness. Roofing usually has a life warranty of between 10-20 years, but adhesives not installed properly can start to become dry and brittle from exposure to UV Rays. The membrane loses adhesion to the penetration once the adhesive loses its effectiveness. This then creates space for water to enter.


Problem no. 1: Difficulties in finding stock
From around June 2022, we have found that fasteners and adhesives stock supplies are a lot harder to find. We received a request from a building owner who was interested in a TPO roof, but the order was put on waitlist with availability of this stock predicted to be available only in 2023. Obviously, things can change in the future and this material may be readily available once more at some point, but right now they are hard to find.

Problem no. 2: Incorrect or faulty Installation
The system of using fasteners and adhesives to create a watertight roofing system has been around for a very long time and will continue to be used for quite a while into the future.
The biggest problem with the use of this material is labor related, in that it is not always installed correctly.

We strongly recommend that you find a roofing company that is trustworthy in this regard. It could be worth your while to ask potential roofing contractors to supply you with a list of references that you can contact to verify their workmanship on previous installations.
Confirm that they have successfully installed roofing that has remained leak-free for at least 10 years.


Advantage no. 1: Fast and simple installation
During the process of spraying foam or applying a roof coating system, the process of application is not changed when a penetration is reached. The sprayer continues to operate while spraying around the area of the penetration.
A spray foam installer may need about 1-2 minutes to thoroughly spray around an HVAC unit or other types of penetrations. During the installation of a single-ply roof, the installer may need around 30 minutes to ensure that the area around the penetration is watertight.
Considering that some roofs have multiple penetrations, the process of making sure each one is watertight, can add significant labor hours to your costs. Compared to this traditional roofing system, a self-flashing roof can be installed much faster, resulting in less labor hours, keeping the costs down.

Advantage no. 2: Seamless installation
During the traditional roofing installation process, contractors roll out sheets of material, followed by piecing them together to form a watertight roofing structure. Problems often arise if the seams are not perfectly aligned and matched.

Contractors make use of a variety of methods to seam the sheets together, depending on the material used. Some of these methods include:
· Using heat welding to join the sheets
· Making use of fasteners and adhesives to form watertight seams
· Sometimes they also make use of rocks to aid in holding these sheets or other roofing material together.
These seams are subjected to extreme stress when the roof expands and contracts, which can cause problems with the seams. By choosing a seamless, self-flashing roofing system, the chance of seams separating is completely eliminated.

Advantage no. 3: Avoiding thermal shock
Thermal shock is a term used to describe the damage that can be caused to a roofing system due to abrupt changes in temperature. When your roofing material responds to rapid temperature changes, it expands and contracts too quickly, which can cause damage to certain components of the roof.

There are a variety of different components present in a roofing system and some expand and contract at varying rates. With thermal shock they all change abruptly, at varying levels, which often translates into roof damage.
Thermal shock can cause metal and membrane roofs to move to some degree, which causes the seams to become more visible over time.
With a self-flashing roofing system, there are no seams and rapid changes in temperature does not affect it.

Advantage no. 4: Not affected by lack of stock availability
Earlier we mentioned the challenges involved with stock supplies of fasteners and adhesives. These components are not needed when installing a self-flashing roof.

We hope to have provided you with valuable information regarding the challenges associated with the use of fasteners and adhesives. Furthermore, we are pleased to have pointed out the benefits of a self-flashing roof.
We would like to reiterate that watertight roofs have been successfully installed for a long time, by making use of fasteners and adhesive. The most important aspect of this type of roof installation is to take special care that it is done expertly by the professionals, to avoid unnecessary damage.

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