Page 297 - Construction Waterproofing Handbook

CHAPTER 6

EXPANSION JOINTS

INTRODUCTION

The variety of expansion joints available is almost as numerous as their failures. Leakage
is so common, and failure so expected, that expansion joints are available with integral gut-
ters to channel the water leaking through joints. Manufacturers often recommend installing
a gutter system below joints to collect leaking water. One only has to visit a few parking
garages and view the numerous attempts at collecting leaking water to confirm this situa-
tion. Roof gutters, PVC piping, and metal collection pans are often used in makeshift fash-
ion to collect water leakage.
Leaking water collects salts, efflorescence, lime, sulfites, and other contaminants as it
travels through substrates. This contamination causes damage to automobile paint finishes
and building structural components. There are numerous causes for expansion joint fail-
ure. Among the most prevalent are:

● Selection of one joint for all details
● Improper detailing of joints into other building components
● Improper installation
● Use of too few joints
● Inadequate design
● Joints that are not capable of withstanding existing traffic

EXPANSION JOINT DETAILING

Expectation that one joint design will suffice for all conditions on a single project fre-
quently causes failures. For example, a joint designed for horizontal straight runs is not
appropriate for vertical installations, changes in plane, and terminations into walls or
columns. Many joints are insufficient for 90° turns and changes in plane and often fail if
such installations are attempted. Joint installations at walls or columns that abruptly stop
with no provision for detailing joints into other building envelope components will fail.
Attempts to install expansion joints continuously throughout a deck, including wall areas,
planters, and seating areas, typically fail. Joints at building-to-deck intersections encounter
considerable movement forces, including shear and differential movement, that often
exceed joint capability.

6.1
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