Roof gardens can be divided into two categories: extensive and intensive. Extensive roof gardens, which are more common and less complicated, are typically constructed to a depth of 6” and are frequently designed to meet specific performance goals. Intensive roof gardens, which can be relatively deep, commonly include large plants, trees, and elaborate gardens that require much maintenance. Key benefits of roof gardens include controlling stormwater run-off, mitigating urban heat island effects, and reducing sound reflection and transmission.

Reflective roofs made of thermoplastic membranes composed of thermoplastic polyolefin (TPO) are often recommended because of their high reflectivity and environmental friendliness, qualities that won the approval of the CRRC for Title 24. Fotopoulos Building Industries, Inc. (FBI), representing Firestone Building Products, prescribes TPO membranes to their customer base. Color plays a central part in reflectivity, and the membranes accordingly come in white, tan, and gray. Paul Hatch, the territory manager of FBI’s San Diego market, states that the TPO membranes that FBI uses have a Solar Reflectance Index (SRI) of 102. (The SRI is based on the percentage of heat and light reflected by a roof, and very cool roofs can have values exceeding 100.) Individually, the reflectance of light for TPO is 0.79 or 79%, and the reflectance of heat for TPO is 0.85 or 85%. Another reason that Hatch, and FBI, favor TPO membranes above other reflective roofing systems is that TPO membranes are made of a recyclable material that is high-quality and easy to apply. Hatch says that the TPO membranes are durable, taking traffic better than other waterproofing materials. TPO prefabricated pipe boots are also good for covering exposed pipes on a roof because they preclude the need for black mastic type sealant and require little to no maintenance.

Modified bituminous roofing systems are available in two materials which are commonly used today for low-sloped roofing applications: Atactic Polypropylene (APP) and Styrene-Butadiene-Styrene (SBS). The primary purpose for both of these materials is to provide the weatherproofing cover for the roof assembly. Crude bitumen is a hydrocarbon created naturally from petroleum, and modified bitumen is a blend of other organic materials with a polymer additive of either atactic polypropylene or styrene butadiene styrene. Atactic polypropylene is a plastic additive that gives rigidity and tear resistance to the final product, and styrene-butadiene-styrene is a rubber additive that gives more resilient benefits. These blends are then applied to a base material of polyester or fiberglass. Sheet asphalt paving (mastic asphalt concrete) makes up the majority of bituminous products used in the U.S. Even though bitumen is sometimes referred to as tar or tar-like in its consistency, it is not to be confused with tar. Tar is a product manufactured from coal and is not used as a part of this roofing system.

This topic includes information related to built-up bituminous roofing installed during construction. Built-up bituminous roofing is the most common type of roofing material used on commercial roofs to keep rain water from entering a structure. Built-up bituminous roofing is an assembly of hot-applied or cold-applied waterproof coatings and layered sheets.

This topic includes information related to thermoplastic polyolefin roofing installed during construction. Thermoplastic polyolefin roofing is a type of roofing commonly used on commercial roofs to keep rain water from entering a structure. Single-ply membranes are manufactured from ethylene propylene rubber and available in white, gray or black. Thermoplastic polyolefin roof membrane is either fully-adhered, mechanically fastened or ballasted to a roof surface.

This topic includes information related to fluid applied roofing installed during construction. Fluid applied roofing is used on new and existing low slope and flat commercial roofs to keep rain water from entering a structure and provide an effective energy saving reflective surface. The viscous fluid is applied by a sprayer, roller or brush which creates a monolithic membrane that has no seams.