For flat roof repair and roof sealing, Elastomeric Roof Coatings are the most popular choice today. Asphalt type coatings and built-up roofs are still around, but many of them are being replaced or “covered up” with the new liquid synthetic rubbers.
Most people find that the elastomeric coatings are easier to apply than the rubberized sheets that are also used for waterproofing. If you are repairing a very small section, the sheets may be the best choice. For large jobs, the liquid rubber is less labor intensive.
The liquids are applied like paints and other sealants. Most manufacturers recommend a squeegee for initially spreading the liquid. Then rollers or brushes are used to give you a smooth surface and a uniform thickness. The job is easier if you have two people; one to pour and use the squeegee and another to follow up with the rollers or brushes.
The brushes are for hard to reach areas that you can’t get to with the roller. The better manufacturers provide complete directions including how thick the roller pad should be and the kind of nap that works best.
Before you can use liquid rubber for flat roof repair and roof sealing, you need to find out if the roofing material currently in place will bond with the material. For example, the EPDM rubbers do not bond with asphalt-based materials. A catalyst coating must be applied first.
Silicone-based caulking needs to be removed and replaced with a non-silicone based material. EPDM and other liquid rubbers do not bond with silicone-based materials. Other than asphalt and silicone, most other materials will bond with the coatings.
Temperature extremes can make the coatings a poor choice. If the weather is too hot or too cold, the curing process may not take place. The coating will eventually cure, but it may take longer. Bubbling can occur if it rains before the cure process is completed.
Liquid rubber is not the only solution for flat roof leaks and roof sealing. Even if you decide to use the coatings, you may still need to do some repair-work. The material used to make the repairs need not be waterproof if you do decide to use coatings. Their original use was for waterproofing. They are becoming more popular today for other reasons, including reduced heat and noise transfer.