Roof Coating Case Study -
Modified Bitumen Roof

This is a twenty year old modified bitumen roof over a wood processing plant, so as you might imagine, a leaking roof is not only inconvenient, it is also costly due to down time and ruined product. The first thing that must be done with any roof before coating is power-washing the entire surface. This roof was cleaned using some 3,000 psi to ensure the roofing system would fully adhere to the aged roofing material.

Before applying the roof coating system from American WeatherStar roof coatings, a moisture survey was completed to ensure the roofing substrate and insulation were dry. If wet insulation is found, it must be replaced before the AWS roof coatings system is installed.

After a thorough cleaning, one coat of AWS Acrylic Bonding Primer 905 was applied in order to ensure adhesion of the butyl coating system to the roof substrate. Other suitable primers include AWS Fabric Bond 930 and AWS SBS Primer 950.

At that point, the waterproofing stage began. Every seam and penetration was sealed with AWS Polyester Fabric and AWS Butyl 310. An initial layer of AWS Butyl Roof Coating was sprayed over each seam, then AWS Fabric was meshed down into the butyl coating before a final spraying of another layer of silicone sealer. The same process was done around each penetration on the roof. Since this particular roof had aged to the point where leaks had spread throughout the entire surface, the next step was to apply the fabric to larger areas in the field of the roof.

After the fabric was installed in all the areas of concern, the entire roof was sprayed with two more coats of AWS Butyl 310 to form a seamless, monolithic and elastomeric membrane over the entire roof area. Other appropriate top coats for this type of application include AWS Urethane 520 in low slope applications that don't drain well or Miami-Dade County approved AWS Acrylic 211 in situations where the roof does drain well.

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