Page 42 - Construction Waterproofing Handbook

2.6 CHAPTER TWO

FIGURE 2.6 Typical detailing for foundation drainage system.
(Courtesy of TC Mira DRI)

The systems not only eliminate the need for protection board, but also eliminate the
requirement for special backfill material consisting of sand or gravel materials to promote
drainage. Typically, the existing soil is used as backfill material, reducing the overall costs
of new construction. A typical below-grade wall detailing, using the drainage as protection
for the waterproofing membrane, is detailed in Fig. 2.9.
The systems also provide a drainage flow rate (depending on the size of plastic core struc-
ture, which varies from 4 in to 2 in) 3–5 times the capacity of commonly used drainage back-
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fill materials such as sand or small aggregate fill. The material is obviously lightweight, with
one person capable of carrying the average roll of material that covers as much as 200 ft 2
of substrate, the equivalent of a small dump truck of aggregate backfill.
Materials selected should have a high compressive strength to protect waterproofing
applications (a minimum of 10,000 psf). Also, the system should be resistant to any chem-
icals it might be exposed to, such as hydrocarbon materials at airports.
Among the many advantages of manufactured drainage systems over conventional
aggregate backfill:
● Cost effectiveness.
● Attached filter fabric or geotextile eliminates the usual clogging of traditional systems.
● High-strength material can be used in lieu of protection board for membranes.
● Provides belt and suspender protection for below-grade spaces by quickly channeling
ground and surface water away from the structure.
● Permits backfilling with the excavated soils.
● Lightweight and idiot-proof installations.