Page 298 - Construction Waterproofing Handbook

6.2 CHAPTER SIX
For expansion joints to function properly over a range of in-place service requirements,
they must include manufacturer details, design accessories, and systems components for
the following common installations:

● Floor joints
● Wall-to-floor joints
● Building-to-floor joints
● Intersections with curbs
● Intersections with columns
● Joints at ramps
● Ramp-to-floor joints
● Intersections of two or more joints
● Changes in direction
● Joint terminations

Other common problems are connections between joints and substrates. These connec-
tions must withstand movement occurring at joints, or they will be ripped away from the
substrate. If sufficient protection from traffic conditions is not provided, traffic wear over
a joint might eventually break down or damage connections.
Often joints are not designed for the shear or lateral movement occurring in parking
decks, especially at ramp areas. When an automobile travels over a joint, live loads
induced by the automobile cause one side to lower while the opposite side remains level.
Reverse action occurs after the auto passes over the joint. This shear stress can be felt by
standing directly over a joint when automobiles cross.
Joints must be designed to withstand shear loading in addition to expected expansion
and contraction movement. Expansion joints, such as T-joints, with a metal plate beneath
the sealant portion, often fail because shear movement forces the plate into the sealant, rip-
ping it apart.
For expansion joints to function when in place, they should also have the following
components:
● Connection details for installation to structural components
● Connection details for waterproof coatings or membranes
● Protection against vehicular and snow plows
● Channeling of any water that might collect
● Cleaning provisions to remove accumulated dirt (e.g., leaves)

Expansion joints do not alleviate all movement encountered with deck construction.
Concrete may crack at short distances from expansion joints due to shrinkage, settlement,
or differential movement. This is common with double-T precast construction incorporat-
ing a topping slab. At each panel joint, the topping slab is subjected to differential move-
ment and will crack over each T-joint, regardless of how large an expansion joint is
installed. Therefore, adequate allowances must be made for settlement and for differential
and structural movement, which expansion joints alone cannot resolve.