General Contractor Houston EPDM Commercial Roofing
UNDERSTANDING LOW-SLOPE ROOFING SYSTEMS Very few people are experts on every kind of roofing system. However, the various types of low-slope roofing systems frequently considered for schools basically can be divided into two categories: multi-ply or single-ply. Multi-ply systems generally are bitumen-based (asphalt or coal tar), while single-ply includes polymer and metal systems. Several factors should be considered when selecting a roofing system. The installation design, its application and potential problems are important when determining the optimum system for a particular building. Another consideration is the environment. Although there are no nationwide programs to recycle roofing waste, some materials can be recycled or put to use in other ways.
EPDM Description: These roofing systems are made from large sheets of synthetic rubber that are placed on the roof and seamed in place using adhesives or special tapes. The roof is complete in a single layer; thereby the term single-ply.
The rubber used in these systems is ethylene propylene diene terpolymer (EPDM)-a synthetic polymer that is blended with carbon black, oils and other additives to make a weather-resistant and thermally stable membrane sheet. EPDM and other single-ply membranes are attached to the building using one of three techniques:
-Ballasted is the most common attachment method for EPDM, and uses stone (nominally 11/2-inch diameter) or concrete pavers (typically at 10 to 12 pounds per square foot) to resist wind-uplift forces. The membrane is laid over loose-laid or attached insulation boards, or other substrates, and then seamed together. It is then covered with the ballasting material.
-Mechanically attached systems use rows of fasteners to hold the membrane to the roof deck. Wind and thermal forces are transferred from the membrane to the fastener and, ultimately, to the deck. These systems typically use a reinforced membrane and are designed with row and fastener spacing set to meet wind-uplift-requirement needs; thus varying greatly between manufacturers and individual jobs.
-Fully adhered is the last anchoring technique and involves the use of either a contact adhesive, sprayed foam, or asphalt to attach the rubber to the top of an insulation layer or other substrate. The type of adhesive used will depend on the type of membrane. Fleece-backed EPDM is needed with spray foam or asphalt. The contact adhesives contain flammable solvent; thus there should not be any open flames on the rooftop during installation, and steps should be taken to keep solvent fumes out of the building.
Ideal Application: EPDM is best suited for roofs with vast, open areas where the large panel size allows fast installation. The roofs should also not have much traffic.
Potential Problems: The major concerns with rubber roofs are cuts, tears and seam strength. Other issues with ballasted roofs, due to the ballast, are the weight of the ballast and the difficulty in inspection and finding leaks. It is recommended that walkways are provided to allow easier movement across the roof.
