26 September 2006
manufactured in the United States. When this material is found in existing installations
it must be replaced as part of the project and may not be specified for use. An in-depth
evaluation of the metal deck condition is required when phenolic foam insulation is
Tapered Insulation Systems. Tapered rigid board roof insulation
systems are more expensive per square unit than non-tapered insulation. As a result,
do not use tapered insulation to create the primary slope in new construction. Use
tapered insulation in crickets and saddles to ensure positive drainage when adequate
drainage already exists in the roof deck as a whole.
Silicon-modified gypsum board. Commonly used as a recover board
provides improved impact resistance to single ply membranes and improved fire
OVERVIEW OF ROOF MEMBRANES.
The NRCA Manual discusses all available roof membranes, however, some
membranes do not provide the long-term performance objective of military buildings.
Some new products may not be judged suitable because of the lack of proven
performance. Other existing membrane systems may not be suitable because
experience has shown a lack of cost effectiveness over the required life cycle.
Types of Membranes.
Generally roof membranes that are suitable for use by the military are limited to the
a. Hydrostatic metal roofing (covered in Chapter 4).
b. Built-up roof membranes.
c. Styrene butadiene styrene (SBS) or Atactic polypropylene polymer (APP)
modified bitumen membranes.
d. Ethylene propylene diene monomer (EPDM) single-ply membranes.
e. Weldable thermoplastic polyvinyl chloride (TPC) single-ply membranes.
f. Spray applied polyurethane foam (SPUF) membranes.
Other Roof Membranes.
Other roof membranes will be considered and evaluated on a case-by-case basis.
GUIDANCE FOR ROOF MEMBRANES.
This Section provides requirements and considerations for the design and construction
of the above roof membrane types.