field-applied coating. After the factory-applied surface has deteriorated
(about 10 years in the tropics) the EPDM membrane can be field-coated for
EPDM sheets are produced in various thicknesses; but only consider
the 60 mil thickness for use. The usual insulation for EPDM roofing is a
composite urethane/perlitic fiberboard which is installed with the perlitic
fiberboard to the roof in hot asphalt and the EPDM to the urethane side with
adhesives. EPDM roofing is not resistant to grease and oil and cannot be used
Modified Bitumen. This sheet membrane roofing does not yet have an
extensive track record for installation in a tropic humid environment. The
single-ply membrane is composed of bitumen modified with plasticizers.
Modified bitumen/reinforced (MB/R) membrane includes a reinforcement at mid-
depth with a glass fiber or similar reinforcing mat. Total membrane thickness
for MB/R is about 160 mils (slightly less for non-reinforced membranes). The
membrane is bonded to the substrate in its own hot asphalt with a torch
applied to the membrane as it is rolled into place.
If this system is applied over urethane foam insulation, first
protect the insulation with another layer of rigid perlitic fiberboard
insulation with joints staggered over those of the urethane board below. If
insulation is required, if at all possible, place the insulation inside under
the roof deck. It is recommended that modified bitumen membrane not be
installed on roofs with a slope of less than 1/2 inch in 12 inches. Modified
bitumen membrane is not tolerant of ponding water.
Elastomeric Roofing. Fluid-Applied
Elastomeric Liquid Rubber Coatings.
These will provide a highly
reflective surface that will remain so for many years. Such a coating will
Material, whether it be urethane, silicone, or acrylic has the following
a) The material has high solids liquid, 60 percent or greater,
volume solids and must be resistant to ultraviolet light.
b) It must be capable of at least 150 percent elongation and
recovery and must adhere to the substrate.
c) The material selected must withstand ponding water, especially
if the roof slope is less than 1/2 inch in 12 inches, and if the coating is
protecting topside insulation.
Elastomeric liquids are usually applied to a clean,
dry substrate with airless spray, brush, or roller. The coating is self-