Page 198 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.87
Most systems allow for seamless applications; this makes termination and transitional
detailing easily detailed within the roofing installation. Modified bitumens are also used as
protected membranes with inverted roofing systems. They are typically manufactured from
a basic asphaltic product with added plasticizers and proprietary additives. This provides
better performance characteristics as compared to basic asphaltic systems.
Generally, modified bitumens are not resistant to heavy pedestrian traffic. Adequate
measures must be taken to provide for walkway pads or other protection. As with single-
ply systems roofing, applicators are approved and trained by material manufacturers. (See
Table 3.27.)

TABLE 3.27 Modified Bitumen Properties
Advantages Disadvantages
Increased performance properties Thickness control of applications
Seamless applications Temperature control of hot-applied systems
Termination and transition detailing Safety concerns

Metal roofing
Metal roofing systems on many building envelopes are used as decorative highlights for
small portions of the entire roofing area. Often, metal systems such as copper domes are
used for aesthetic purposes.
Complete metal roofing systems are now used regularly, especially on low-rise educa-
tional facilities and warehouse-type structures. Metal roofing systems are available in a
variety of compositions, from copper to aluminum. They also include various manufac-
tured preengineered systems.
Termination and transition detailing are difficult with metal systems, particularly when
large amounts of rooftop equipment are installed. Additionally, metal roofs are not recom-
mended for flat or minimally sloped areas that frequently occur on building envelopes.
Metal or sheet flashings are typically used for transitional detailing. This makes round
protrusions and sloped areas subject to problems in detailing and possible water infiltra-
tion. If used in proper situations and expertly installed, however, certain roof systems such
as copper domes will far outlast any other type of roofing installation. (See Table 3.28.)

Sprayed urethane foam roofing
Sprayed urethane foam roofing systems consist of high-density urethane foam coated with
an elastomeric roof coating. The foam is of sufficient density to withstand minor foot traf-
fic. The elastomeric coating, although similar to that used for vertical envelope water-
proofing, must be able to withstand ponding or standing water.

TABLE 3.28 Metal Roofing Properties

Advantages Disadvantages
Aesthetics Termination and transition detailing
Durability Not for flat or minimally sloped roofs
Life-cycle weathering Cost