Modified Bitumen Flat Roofing and Repair

Modified Bitumen is an evolution of asphalt roofing. It is made from asphalt and a variety of rubber modifiers and solvents. There are several ways of connecting pieces of this material. In a heat application process the seams are heated to melt the asphalt together and create a seal. There are also hot-mopped tar applications with layered fiberglass sheets, called built-up roofing. Cold-applied adhesives and self-adhering membranes are two of the more recent options. This material is also referred to as APP (atactic polypropylene) and SBS (styrene-butylene-styrene).

MRC Roofing provides time-tested, reliable fully integrated, long lasting roofing systems in cold- or hot-applications and a range of modified bitumen performance levels; all of which provide exceptional waterproofing protection for your building.

It’s important to verify that there is positive slope in the roof structure to ensure proper drainage. Over time, wood structures with to low of a slope can sag and cause ponding conditions. Completely flat roofs or roofs with negative slope need to be re-engineered with a minimum rise over run of ¼”:12” up to a preferred 2”:12” slope.

By building code and manufacturer’s specification, a licensed contractor can not install low slope roofing on a perfectly flat roof or a roof with negative slope. Slope is best created by installing a tapered system of Styrofoam or expanded polystyrene (EPS) to the roof deck structure, ensuring positive slope to the eaves or drains. This is commonly done on both residential and commercial buildings.

Negative sloped roofs void manufacturer warranties because of ponding. This situation tends to be an issue here in Hawaii. Many architects and builders over the decades have come to Hawaii and built flat roofed homes when building codes were lax. This happened especially on Oahu. This situation cannot be repaired. This kind of situation calls for reroofing with a tapered system or coating with a water impermeable silicone coating (more cost effective).

MRC has installed thousands of low slope roofs in Honolulu county. Low-slope roofing materials have evolved as materials technology improves. MRC now installs self-adhering modified bitumen cap sheet systems with a proven track record. The life expectancy of a properly installed modified bitumen roof in Hawaii is 30 years and that life expectancy can be extended drastically with a coating of silicone.

Another tactic used to extend the life expectancy of modified bitumen roofing is proper ventilation. This can be achieved with the use of solar attic fans, installing Energy Star/CRRC rated reflective colors and choosing a cap sheet that is algae resistant.

To ensure our customers move forward with a low slope roof with a long-life expectancy, MRC provides a free inspection service with our quotes. Please give us a call.

808-842-4464