Expansion Joints and Control Joints

Expansion Joints play an important role in the overall stability and longevity of a parking deck structure. Deck exposure to hot and cold temperature cycles may cause the expansion or contraction of the deck’s structural components. This thermal movement, if not compensated for by way of an “expansion joint” system, will create internal stresses to occur in the structural members. Stresses of this nature may cause the following deleterious conditions:

  • Perimeter foundation walls to move and crack due to lateral pressures.
  • Pavement surfaces to buckle (heaving) under displacement of underlying structural components.
  • General deflection (sagging) of structural components.
  • General displacement at beam support connections.

The resulting effect of these internal stresses (as listed above) will eventually compromise the structural integrity of the deck as well as deteriorate the waterproofing membrane system. Deteriorated waterproofing can lead to exponential deck deterioration as moisture infiltration exacerbates the development of freeze-thaw cycle stresses within the structure.

Parking decks that have been constructed with expansion joints sometimes require the replacement of failed expansion systems. Exposure to the elements and snow and ice removal from decks may eventually deteriorate and fatigued expansion flexible components. Also the vibration caused by vehicle traffic moving across the expansion joint can eventually lead to system failure. Common failures of expansion joint systems are as follows:

  • Brittle membrane that has lost flexibility.
  • Membrane tears and detachment from frame components.
  • Failed sealant at joint transitions to deck slab.
  • Detachment of frame components to deck slab.
  • Sagging membrane across expansion joint.

Replacing deteriorated expansion joints has its challenges – especially when the parking garage is a steel and metal deck system. A variety of expansion joint systems are manufactured including retrofit systems that expand and create a pressure seal to adjacent components. Proper evaluation and engineering are critical to develop a successful replacement protocol.

Installing an expansion joint in a structure where one does not exist requires a complete rebuild of the immediate structural deck components to completely separate (isolate) the adjacent slabs from any contact except for the expansion joints. This may not be advisable as the influence of a created expansion joint in the parking deck may have an undesirable effect to the remaining building without an expansion joint.

(Boccia, EBI) has encountered parking garage decks that have been originally constructed with no expansion joints that experience all (or part)of the above listed conditions. Photo examples are as follows:
Lateral forces causing cracks to the perimeter foundations.