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Split-slab Waterprooﬁng in
High-load Trafﬁc Environments
Designing a high-performing concrete topping slab
by Lyn S. Kent, AIA, John F. Sumnicht, SE, and Daniel G. Gibbons, PE
All images courtesy Simpson Gumpertz & Heger
DESIGNERS OF COMMERCIAL AND
INSTITUTIONAL BUILDINGS IN URBAN
SETTINGS OFTEN WORK ON CONSTRAINED
SITES WHERE THE SERVICE AREAS
EXPOSED TO WEATHER OR WASH-DOWN
ARE LOCATED OVER OCCUPIED SPACES
BELOW. WHILE THE REQUIREMENTS TO
PROTECT THESE SPACES FROM WATER
INTRUSION ARE UNDERSTOOD AND
DOCUMENTED, THIS IS NOT THE CASE
FOR THE WEARING SURFACE OVER THE
WATERPROOFING SYSTEM, ESPECIALLY
WHEN IT COMES TO LOADING DOCKS AND
OTHER HIGH-LOAD TRAFFIC ENVIRONMENTS.
There are several wearing surfaces that can be used
over waterproofing installations, but a concrete
topping slab is often the best protection for high-
traffic service areas as it can take the abuse and
heavy loads. Further, the material is fairly easy to
maintain, provided cracks in the slab are minimized.
In split-slab applications, the most reliable
waterprooﬁng membrane assemblies form a long-
term watertight seal over the structural slab substrate.
This type of system typically consists of a layering of
components such as a waterprooﬁng membrane, a
protection layer, and a drainage layer. However, since
these systems are compressible, the concrete topping
slab must be designed to be placed over top.
22 the construction speciﬁer | january 2013
12/12/12 9:33:07 AM