Modified Bitumen Flat Roof

A Modified Bitumen is a key element in any built-up roof.

This type of roofing system was developed in Europe during the sixties and later introduced in the U.S. in the early seventies. Modified refers to the addition of plastic or rubber-based polymeric binders to the asphalt or “bitumen” to improve its roofing performance and durability. Modified Bitumen Flat Roofs are usually assembled using one, two or three plies.

The Modified Bitumen Membrane is made up of multiple layers in what is essentially a “factory assembled” built-up roof. During the roofing manufacturing process, several coats or laminations of modified bitumen are reinforced with a woven fiberglass, or polyester fabric reinforcing mat or a combination of both. They are then finished with either a smooth or granular top surface.

The Granular type comes in different colors. The smooth surface type is then coated with either an aluminum or white surfacing on site. The coatings are used to deflect the damage from ultra-violet rays from the sun as well as keeping the roof surface cooler.

Modified Bitumen Roofs exhibit many characteristics of a built-up roof (BUR), yet affords the ease of application on a single-ply roof. This offers various specifications which allow for multiple plies, which provide redundancy and exceptional resistance to heavy traffic, punctures and tears. Modified Bitumen membranes also have low-temperature flexibility and are resistant to membrane fatigue(break down).

There are two types of Modified Bitumen Systems

  • APP (Atactic Polypropylene) roofs are applied using a heat-welded method. The top surface comes in either smooth or granular. The consistency and uniformity of the factory produced sheet results in a membrane that has greater stability and flexibility than that of a laminated built-up roof system.
  • SBS (Butadiene Styrene) roofs are usually applied using hot asphalt, bonding adhesives, heat welding or heat activated self-adhesives. The top surface is a mineral granular of choice of colors. It has the benefits of a built-up redundant system with the quality of a factory single ply membrane.

flatroofs.ie employ expert technicians and are qualified to install modified bitumen roofing on any commercial and industrial flat roofing system in Ireland.