2 FM quick reads on Roof membranes
1. When a Roof Straddles The Repair/Replace Line
Although all roof membranes have different physical properties and failure modes, there are certain deficiencies that are common to all roof membranes. Here are some common failure modes for all membranes to look out for:
Brittleness: All roof membranes become brittle at the end of their service life. This phenomenon is more rapid in some membranes. Once the material becomes brittle it loses the elasticity required to provide weatherproofing service. The material can be tested through tensile or elongation tests to determine remaining service life or failure can be illustrated through grazing and cracks and splits in the membrane surface. Visual observation of material scrim or reinforcement is also an indication of material failure.
Wet Insulation: All roof insulations lose structural and thermal integrity once they are wet. All wet insulation should be removed from the system to avoid costly structural deck damage, particularly on metal decks. Typically, if more than 25 percent of a roof system has wet insulation a full roof replacement is recommended. Wet insulation can be determined by any method of moisture testing. If non-destructive moisture testing is conducted gravimetric testing should be conducted to verify that the material is wet. Some adhered membranes will illustrate wet insulation through excessive blistering and membrane ridging.
Flashings and penetrations: Flashings and penetrations are the most vulnerable point of a roof system and nearly two-thirds of all roof leaks occur at these points. Openings, splits and sagging of flashings materials are common causes of roof leaks. Excessive openings or displacement of these materials can lead to free flow of moisture infiltration into the system and the building.
2. What You Need To Know About Flat Roof Coatings
Flat roof coatings can be a good investment for many facilities. A flat roof coating can extend the life of a roof because it lowers the roof temperature. It can also lead to additional energy savings as the temperature is reduced.
Still, because there are so many different types of roofs in use today, specifying a flat roof coating isn't easy. Different substrates require different coatings. A coating's adhesion might depend as much on the substrate's characteristics as on the coating type. In general, it is more difficult for coatings to adhere to hard, smooth, chemically inert surfaces and easier on rough, irregular, chemically active surfaces.
A coating's adhesion to a substrate often improves when the installers put down a primer or base coat. Coatings manufacturers recommend certain primers or base coats for managers trying to match a specific topcoat with a specific substrate. Managers should use only the base coat or primer specified by the coating's manufacturer.
With the introduction of roof membranes such as ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC), thermal polyolefin (TPO), Hypalon, modified bitumen, and built-up roofing, manufacturers have developed a variety of roof coatings to address multiple substrates with different adhesion and weathering characteristics.
Managers can specify asphaltic and tar-based coatings for use with coal-tar-pitch built-up roof systems. Non-asphaltic coatings, including urethanes, acrylics, and polyureas, are most commonly used on single-ply systems.
Each of these coatings has different cost and performance factors. Due to variations in coating formulations, a manager should work closely with a roof consultant and the manufacturer to make sure they specify the right coating for the roof substrate and that workers perform the correct repairs before applying the coating. Manufacturer representatives and product data sheets also can assist in specifying coatings.
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