Page 28 - Construction Waterproofing Handbook

1.10 CHAPTER ONE
Roofing. That portion of a building that prevents water intrusion (usually from gravita-
tional forces) in horizontal or slightly inclined elevations. Although typically applied to the
surface and exposed to the elements, roofing systems also can be internal, or sandwiched,
between other building components.
Below-grade waterproofing. Materials that prevent water under hydrostatic pressure from
entering into a structure or its components. These systems are not exposed or subjected to
weathering such as by ultraviolet rays.
Above-grade waterproofing. A combination of materials or systems that prevents water
intrusion into exposed structure elements. These materials can be subject to hydrostatic
pressure from wind conditions and are exposed to weathering and pollutant attack.
Dampproofing. Materials resistant to water vapor or minor amounts of moisture that act
as backup systems to barrier systems or an integral part of drainage systems.
Flashing. Materials or systems installed to redirect water entering through the building
skin back to the exterior. Flashings are installed as integral components of waterproofing,
roofing, and dampproofing systems. They also can act as divertor systems.
Diversions. Diversions redirect water being forced against envelope components and
divert it elsewhere before it infiltrates or absorbs into the substrate. Examples include
flashings, downspouts, sloped concrete decks, and drainage mats.
Building envelope. The combination of roofing, waterproofing, dampproofing, flashing, and
divertor systems in combination with all exterior facade elements acting cohesively as a com-
plete barrier to natural forces and elements, particularly water and weather intrusion. These
systems envelop a building or structure from top to bottom, from below grade to the roof.
The entire exterior building skin must be enveloped to prevent water infiltration. It is
important to recognize that every component used in the envelope or building skin must be
waterproof. This would include many features that most people do not recognize as hav-
ing to be waterproof to maintain the integrity of the envelope, including exterior lighting
fixtures, mechanical equipment, signs, and all other types of decorative features.
Each item used or attached to the building envelope should be made waterproof and
then appropriately connected to other envelope components to ensure that there are no
breaches in the envelope’s integrity. All envelopes contain combinations of several sys-
tems, such as the building’s main facade material (e.g., brick), glass curtain walls or punch
windows, and decorative features such as concrete eyebrows.
These main facade elements are typically barrier waterproofing systems (e.g., glass is
actually a barrier system) or drainage systems, as in the case of brick. Installing divertors
where necessary or appropriate for additional protection against water infiltration then
completes the envelope.
Each individual system then must act integrally with all others as a total system for
complete effectiveness as a weather-tight building envelope. Figure 1.9 illustrates the inter-
relationships of the various components of a simplified building envelope.
In Fig. 1.9, the horizontal roofing membrane terminates in a vertical parapet at the metal
counterflashing that also transitions the parapet waterproofing into the membrane roofing. In
this specific case, the flashing acts as a transition component between the roofing and parapet
materials and ensures the watertightness of the envelope at this transition, enabling these two
separate components to act cohesively.
A similar detail occurs at the coping cap. This flashing detail provides transition-
ing between the brick facade, water repellent on the brick, cavity-wall dampproofing,