A roofer performing an adhesion test on a roof coating
Technical Bulletins

How to perform an adhesion test on a roof

December 1, 2022
Discover the importance of adhesion testing, its optimal timing, and the correct methodology for accurate results. Gain valuable insights into this critical process, including when and how to perform it effectively.

Adhesion testing

is recommended over all applicable roof surfaces prior to any coating system application.  This Technical Bulletin will outline the steps for performing adhesion testing in the field and interpreting results.

Preparation of Substrate

·      Determine substrates areas to test.  For best results, perform three (3) adhesion tests over all surfaces present.

·      Clean surface using 799 Wash-N-Prep, plastic scouring pad, water and rags or other means to simulate the roof surface preparation process. All surfaces should be dry and free from any loose coating, debris, grease or oils.


·      Apply coating to the cleaned surface in an area 4” wide by 6” long with standard 3” chip brush or small 4” roller.

·      Immediately imbed6” of an 8” long by 1” wide strip of Resat-Mat into the wet coating.  The 2” of the fabric hanging out will be used to pull to check for adhesion.  

·      Smooth fabric out with brush to completely saturate in the coating.  There should be no wrinkles or voids.

·      Apply another layer of coating overtop the fabric to completely encapsulate.

·      Allow to dry 14days for proper curing of the coating. Curing time dependent upon temperature and humidity.  

Adhesion Test Pulls

Using a digital hanging scale or “Fish Scale”

·      Take a 1” long piece of duct tape and wrap it over the end of the uncoated fabric tab.

·      Using the hook end of a digital hanging scale, pierce through the duct tape and fabric.

·      Pull hanging scale upward, perpendicular to the roof surface slowly.  The peak or highest value shown should be above 2 pounds of force.  Record highest number obtained.  

·      Visually inspect pulled fabric strips and compare to diagrams and explanations below.

How do I know if it was successful or a failure?

The Results:

Coating Adhesion Failure Scale:  

A 1 to 5 scale: 5 being the BEST RESULT

1 – Coating peels off substrate completely attached to fabric strip with minimal effort. Think ‘Post-It Notes’ removed from paper.  Fabric pulled at 90° with less than 2.0 lbs. of force.

2 – Coating peels off substrate with fabric strip, some coating remains adhered to substrate.  Remaining coating on substrate can be picked off with little effort. Fabric pulled at 90° with less than 2.0 lbs. of force.

3 – Coating peels off substrate but considerable effort is required.  Fabric pulled at 90° with greater than 2.0 lbs. of force required.

4 – Fabric strip can be lifted using force but coating separates.  Coating comes up with fabric as well as coating remains over a majority of the substrate.  Fabric pulled at 90° with greater than 2.0lbs. of force required.

5 – Coating exhibits high adhesive and cohesive strength.  Difficult to pull fabric from substrate, may result in fabric tearing.  Fabric pulled at 90° with greater than 2.0lbs. of force required.

Examples of Adhesion Test Failure

Examples of adhesion test failure
So in end, after performing all of the steps and then doing a pull test, you will know if the chosen coating is appropriate for your entire roof, and will last for many years.

Happy Adhering!

Check out this video of an adhesion test

The Karnak Team

Since 1933, our team at KARNAK has been dedicated to producing top-quality sustainable roofing and building solutions that protect and extend the life of building envelopes while reducing environmental impact. As a family-owned and certified woman-owned business, we pride ourselves on our commitment to quality, durability, and personalized customer service. We specialize in liquid-applied roofing systems, repair products, and comprehensive support through detailed documentation and our Q Applicator Program for contractors.

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