Preparing Your Commercial Roof for a Roof Coating

Oct 10, 2022Blog, Commercial Roofing, Roof Coating

Once your commercial roof contractor has correctly identified the composition of the substrate and has determined it to be sound and dry, the next step is repairing flaws and preparing the surface for coating. Above all, the application surface must be smooth, and free of grease, wax, dirt, contaminants, moisture, and other matter, which would interfere with adhesion. It must also be free of loose roofing material or other debris.

You will need to consider many factors when preparing your substrate, a few of which we have listed below for your consideration:

Proper Aging of the Roof

Consider the age of a built-up asphalt roof. Before applying the coating over recently-applied asphalt roofs, it is necessary to allow the asphalt to dry and cure properly. Asphalt must be free of oil or solvent surface residues in order to permit proper bonding of the coating. Consult the proper curing times chart for curing times. Under poor weather conditions, longer periods may be required.

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Preparation of Built-Up Roofs

Built-up roofs are prone to multiple different signs of age. Exposure to ultraviolet light over time gradually causes loss of flexibility, encouraging brittleness and the inability to tolerate the normal expansion and contraction that occurs on a roof. Severe deterioration (more than 30%) requires tear-off and replacement with an approved substrate. The following are brief descriptions of many of the common problems and the treatments required prior to normal cleaning procedures.

  • Splitting in a roof can result from a number of conditions. It could be substantial movement in the roof deck causing stress and resulting in cracks. It could also be a result of the roof becoming dry, brittle, and intolerant of the normal expansion and contraction of the roof deck.
  • Blistering is a sign of trapped moisture. All blistered areas must be removed with the underlying insulation checked for dampness and replaced if necessary. An approved roofing material such as polyurethane foam or boardstock must then be used to fill in the void before coating.
  • Gravel Turnover occurs on thick built-up asphalt roofs. Here, the aggregate frequently sinks below the surface, bringing the asphalt to the top. This is indicative of excessive thickness and weight, either in isolated areas or over the entire roof surface. All such areas must be replaced with approved materials before coating.
  • Felt Exposure indicates that the asphalt has eroded away completely from certain areas, leaving a dry, brittle, and unstable surface. Any portion of the roof where felt is visible must be removed. Replacement with approved roofing materials is required prior to coating.
  • Delamination can refer to the separation of the various layers of a built-up roof or can refer to the actual pulling apart of the lamination of a plywood panel. In either case, an unacceptable substrate condition exists. The affected areas must be removed and replaced with approved materials.

Removal & Replacement Guidelines

  • Some rules to keep in mind whenever replacing faulty or deteriorated roof sections are:
  • Always use approved roofing materials in your replacements.
  • Ensure that the new surface is uniform; this will simplify the applications of your coating product.
  • Avoid the use of caulking compounds to fill in large gaps or voids; caulk may extend drying times.
  • After removing any portion of a roof, the same rules apply for the cleaning and preparation of the surface. Any dust or debris resulting from the repair procedure must be removed. The whole surface must be cleaned and dried before coating can take place.

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Cleaning the Roof

Assuming that all necessary repairs have been made to an existing substrate, you may proceed to the next step in surface preparation, cleaning the roof. Many types of equipment are available to provide the best possible cleaning for each roof. In general, a dry method of preparation is initially recommended. Professional sweepers, power brooms, scratchers, power blowers, and similar roofing equipment should be used to remove any loose material from the roof. It is crucial that cleaning be thorough and complete. The longevity and performance of your roofing system depend on it!

When you’re getting ready to coat your commercial roof, trust the team at Denver Roof Coatings to get the job done right! Call today for a free estimate.