Adhesion testing of waterproofing and roofing materials to the substrate

What can be tested

• coating (paint-on) waterproofing
• mastic coatings
• polymer waterproofing compounds
• cement-polymer waterproofing
• protective coatings on concrete structures
• bonded roofing and waterproofing membranes
• individual roll materials, where the substrate bond test method is applicable

The pull-off method does not apply to loose-laid or mechanically fastened membranes, since their performance is not based on continuous bond with the surface.

When testing is required

• after waterproofing has been applied
• before installing the protective layer, screed or finish
• upon acceptance of the contractor's work
• when blistering or delamination appears
• when inspecting a trial area
• when selecting the substrate preparation technology
• for comparing materials or application methods
• when surveying a roof or waterproofing system

How the pull-off test is performed

1. We study the project and the requirements for the waterproofing system.
2. We select control areas.
3. We prepare the surface of the coating.
4. We bond metal test discs to the coating.
5. Once the adhesive has cured, we make a local cut around the disc through the coating, if required by the procedure.
6. We apply a perpendicular pull-off load using an adhesion tester.
7. We record the pull-off force.
8. We calculate the bond strength.
9. We identify the location and nature of the failure.
10. We compare the result with the project requirement.

Why the number alone is not enough

• between the coating and the substrate — adhesive failure
• within the waterproofing material — cohesive failure of the coating
• through the body of the concrete — bond exceeds the strength of the substrate
• between the disc and the adhesive — the result does not characterise the waterproofing, and the test must be repeated
• mixed failure — the share of each failure type is stated

Such analysis reveals not only the pull-off force but also the weak link in the whole system.

What the test shows

• quality of substrate preparation
• correctness of material application
• actual bond of the coating to the surface
• uniformity of the result across different areas
• feasibility of proceeding with the next layer of work

High adhesion alone does not confirm the watertightness of the whole structure. Joints, junctions, penetrations and coating damage are checked separately.

Deliverables for the client

• test report
• layout of the control points
• actual bond strength values
• mean value for the tested area
• description of the nature of failure
• photographs of each control point
• comparison with the project requirements or manufacturer's documentation

Applicable standards

For coatings on concrete and reinforced concrete substrates, GOST 28574-2014 applies, which establishes the method for determining the adhesion of protective coatings by the normal pull-off method.

Within the accreditation scopes of Uzbek laboratories, GOST 26589-94 is applied for roofing and waterproofing mastics. It regulates laboratory testing of the material itself, including the bond strength between layers, and must not be presented as a field pull-off method for a coating from a concrete substrate.

Source for verifying GOST 26589-94 in Uzbekistan: Uzbek laboratory accreditation scope

For a specific project, the test is performed according to the applicable procedure and the project requirements — the exact standard is agreed with the client and stated in the test report.