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Part 3: Proper Surface Preparation is Essential Before Applying Roof Coatings
By Jeffery J. Opel
December 2008 -
Before undertaking a roof-restoration project, managers need to thoroughly understand the existing roof conditions and let these conditions dictate their selection to ensure common repair problems from reoccurring. Open seams, cracks, blisters and other deficiencies require repair before the coating application can begin.
Using infrared technology can help locate wet insulation, which is important because failing to remove wet insulation can lead to advanced deterioration of the membrane and insulation and eventually damage to the deck. Once workers remove the wet insulation and install the new membrane, they can begin surface preparation and the coating application.
Proper preparation of the roof surface is essential before applying any roof coating, and the level of preparation depends on the current condition of the roof. Preparation might be as simple as sweeping, priming and repairing seams.
The surface to be coated must be clean and dry, or adhesion will not occur. If the selected roof coating does not properly adhere to the surface, the coating eventually will disbond from the surface, resulting in an unsuccessful project.
Using a primer is recommended for most surfaces and might be required by the manufacturer before applying the elastomeric coating. In multi-coat applications, workers should apply the base coat at the manufacturer’s recommended film thickness. They should apply the topcoat perpendicular to the base coat, which helps minimize irregularities caused by roller marks.
On days where humidity is low and outside air temperatures are moderate, the elastomeric coatings dry fairly rapidly. On days where precipitation is likely, workers should not install the coating, due to potential run-off.
Today’s elastomeric roof coatings are formulated for use with different types of application equipment, including high-pressure airless sprayers, rollers, and brushes. Whatever the method, workers should monitor application rates with a wet-film-thickness gauge to ensure the proper amount of coating goes on the surface.
Roof Coatings: Bottom-Line Considerations
Part 1: Roof Coating Type Depends on Roof Substrate
Part 2: Roof Coatings Protect Against UV Light, Leaks, Corrosion
Part 4: Managers Should Evaluate Roof Coatings Warranties