Page 102 - Construction Waterproofing Handbook

BELOW-GRADE WATERPROOFING 2.65

FIGURE 2.84 Typical clay system detailing for elevator pit with no mud slab required. (Courtesy of
Cetco Building Materials Group)

● Bulk
● Fabricated paper panels
● Sheet goods
● Bentonite and rubber combination sheets
● Textile mats

Bulk bentonite
Bulk bentonite is supplied in bulk form and spray-applied with an integral adhesive to seal
it to a substrate. Applications include direct installations to formwork or lagging before
foundation completion in lieu of applications directly to substrates. Materials are applied
2
at quantities of 1–2 lb/ft .
Bulk bentonite spray applications provide seamless installations. Controls must be pro-
vided during application to check that sufficient material is being applied uniformly.
Materials should be protected by covering them with polyethylene after installation. Due
to possibilities of insufficient thickness during application, manufacturers have developed
several clay systems controlling thickness by factory manufacturing, including boards,
sheets, and mat systems.

Panel systems
2
2
Bentonite clays are packaged in cardboard panels usually 4 ft , containing 1 lb/ft of bentonite
material. Panels are fastened to substrates by nails or adhesives. Upon backfilling, panels
deteriorate by anaerobic action, allowing groundwater to cause clay swelling for water-
proofing properties. On horizontal applications the panels are simply laid on the prepared
substrates and lapped (Fig. 2.85).
These systems require time for degradation of cardboard panels before swelling and
watertightness occurs. This can allow water to penetrate a structure before swelling occurs.
As such, manufacturers have developed systems with polyethylene or butyl backing to pro-
vide temporary waterproofing until hydration occurs.