WHAT IS THE WATER RUNOFF COEFFICIENT OF EPDM?

There is no exact figure as conditions such as rain water evaporation off a hot EPDM surface are difficult to test. The formula for calculating this flow is called the Maming Formula. The American Society of Plumbing Engineers Data Book suggests that initially there will be some friction along the drainage path but it will quickly go to zero. On a low slope fully adhered EPDM Roof with slope of 1/4″ per foot one could justify a coefficient of .95 to .99. If calculating drainage flow for design or legal matters it is recommended that you contact a plumbing engineer, registered in the state in which the building in question is located.

WHAT ARE MY OPTIONS WHEN DESIGNING AN EPDM ROOF IN AREAS WHERE SEAGULL ATTACK MAY BE PRESENT?

The use of reinforced membranes over a rigid substrate such as Den-Deck, high density wood fiber board and plywood provide excellent protect and both pecking and the dropping of clams to break them open. Additionally placing pavers over any of the EPDM membrane thicknesses would also provide protect as would an IRMA roof system design. Special detailing of the corners, such as double flashings are also recommended. Designers and contractors are suggested to contact the manufacture for specific detailing concerns and potential puncture resistant warranties.

OVER WHAT TYPES OF STRUCTURAL ROOF DECKS CAN AN EPDM ROOFING SYSTEM BE INSTALLED?

The availability of a wide range of accessories and components make an EPDM roof system versatile. For example, the membrane can be adhered directly to wood and structural concrete decks, or mechanically anchored to steel decks. For decks with low pullout resistance (i.e., gypsum, fibrous cement and light gauge steel), special fastening components are available. Ballasted assemblies can be used on any deck as long as the structure is capable of supporting the weight of the installed system. The choice between an adhered, mechanically fastened, or a ballasted assembly may be influenced by the type of structure and its condition.

WHEN RETROFITTING AN OLDER BUILDING, WHAT STEPS CAN BE TAKEN TO INCREASE ITS ENERGY EFFICIENCY WHEN INSTALLING AN EPDM ROOF SYSTEM?

On an older building, lower counterflashings and terminations may hinder the use of thicker insulation; therefore, insulation with greater R Value per inch, like polyiso, may be used. Incorporating two (2) layers of insulation with staggered joints will certainly increase the insulation’s thermal efficiency over using a single layer since heat loss through gaps will be minimized. When the use of multiple layers is not feasible, an inverted assembly may be used in which extruded polystyrene insulation is placed above the membrane.

ON AN EXISTING PROJECT, IS IT NECESSARY TO REMOVE THE OLD ROOF PRIOR TO THE INSTALLATION OF A NEW EPDM ROOFING SYSTEM?

Even though most exiting roofing materials are totally removed in most applications, an old and existing roof may be left in place once the manufacturer’s substrate preparations are followed. The existing roof and roof deck should, however, be inspected prior to re-roofing to ensure compatibility and structural integrity.

CAN EPDM BE USED TO RETROFIT AN OLD METAL PANEL ROOF?

Yes. Insulation is used as filler between the flutes (or ridges) of the metal roof panels and then overlaid with a rigid board. Both layers may be mechanically attached or adhered to the metal panel roof. The EPDM membrane is then adhered to the rigid insulation or mechanically fastened to the structural purlins beneath the metal roof.

HOW CAN DRAINAGE BE ENHANCED ON A FLAT ROOFING INSTALLATION OR ROOFS WITH 1/8 INCH PER FOOT OR LESS SLOPE?

In addition to the number and size of roof drains, drains should be positioned in low areas to eliminate ponded areas. Also, crickets and saddles may be incorporated to divert water and reduce the accumulation of water. If necessary, tapered insulation may be incorporated throughout the roof or in localized areas where additional drainage is needed.

WHAT IS THE AVERAGE UNIT WEIGHT OF NON-BALLASTED EPDM ROOFING SYSTEMS?

The weight of a roofing system varies depending on components used. After combining the weight of components (i.e. insulation, membrane, fasteners, and adhesive), typical installation weight is less than 2 pounds per square foot (10 kg per square meter) when .060″ thick membrane (typically weighing 1/3 pound per square foot or 1.6 kg per square meter) is utilized.

CAN EPDM BE USED ON FREEZER APPLICATIONS?

Freezer applications typically utilize thicker insulation with greater R value (R 40 and above) that subject the membrane to extreme conditions (very hot on a hot day and very cold on a cold day). EPDM is known for its ability to remain stable during temperature extremes and heat-aging testing indicates no changes to physical properties.

CAN EPDM BE INSTALLED AT AIRPORT FACILITIES WHERE JET FUEL EXHAUST IS PRESENT?

There is a misconception in the field that EPDM will degrade with exposure to jet fuel. This is unfounded because jet fuel is in a vapor form and the only degradation from petroleum products is caused by submerging EPDM in liquid petroleum over a prolonged period. There are numerous airport installations throughout North America, the Mideast, and the Far East where EPDM membrane was utilized.