Built up roofing is the most popular substance used on low-slope roofs. Built up roof membranes, referred to by the acronym BUR, have been in use in the U.S. for more than 100 years. These roof systems are usually called “tar and gravel” roofs. BUR systems typically are composed of alternating layers of bitumen and augmenting materials that create a finished membrane. The amount of plies in a cross section is the variety of plies on a roof: The term “four plies” denotes a four ply roof membrane building. Occasionally, a foundation sheet is fastened. Built up roofs typically are considered to be completely stuck if used to insulating material or roof decks.
The bitumen commonly used in BUR roof systems is cold or asphalt, coal tar -applied adhesive. The asphalt or coal tar applied by mop or mechanical spreader and is heated in a kettle or tanker. Asphalt is a petroleum product coal tar is derived from the distillation of coal. Cold-applied adhesives generally are solvent-based asphalts that do not have to be warmed in a kettle or tanker.
Modified Bitumen Systems roofing using modified bitumen membrane roofing systems has grown steadily. Modified bitumen membranes are the quickest growing roofing materials in the business now.
A roof system composed of a built up roof membrane with two or three plies and a polymer-modified bitumen membrane cover sheet is usually called “hybrid” system. NRCA considers this sort to be a polymer modified bitumen membrane system.
Make sure bitumens and mats used for BUR systems meet standards.
The subsequent generally referenced ASTM International standards apply to substances used in the building of BUR systems:
The multiple layers of bitumen and bitumen saturated “felts” make a water resistant barrier effective at supplying many years of dependable protection from the elements
Demonstrate extraordinary opposition to the conduction of heat between inside and the outside of a building, leading to noticeable decreases in cooling and heating costs.
Fire and Uplift Resistance
Examined through FM Approvals and Underwriters Laboratories ensure sufficient uplift resistance under extreme wind conditions and to satisfy very severe fire resistance requirements.
In comparison with other high performance commercial roofing systems, built up roofing is among the greatest investments in the marketplace due to its competitive price per year of service life that is anticipated.
It is vital to get safe bonding of the roofing felts (plies) using bitumen. To reach this bond the roofing contractor uses thin, uniform moppings of bitumen. This ensures appropriate adhesion for fusing and waterproofs the system the membrane system jointly. The temperature of the bitumen is essential. The roofing contractor gets the correct viscosity for appropriate mopping by warming it to the appropriate temperature.
The use of Built Up Roofing systems is the professional who pays special attention to those details including curbs, walls, flashings or other projections that interrupt the membrane, although in-depth work, attains a quality, efficient, long lasting merchandise for the building owner.