Built-Up Roof 3 : Roofing composed of three to five layers of asphalt felt laminated with coal tar, pitch, or asphalt. The top is finished with crushed slag or gravel. Generally used on flat or low-pitched roofs
Complete Design, Inc. (Construction Design Specialists), Dictionary of Construction Terminology, Washington, USA 2015. http://completedesign.cc/client-resources/dictiona ry-of-construction-terminology, (Const - Amer) {836}