11.3. Floor Conditions

Description: Since building expansion joints are designed to isolate sections of a building, they inevitably cut through floors. Copper and copper alloys can be used in floor expansion joints in two ways: as trim and cover plates, or to prevent the flow of water through the expansion space.

Copper waterstops are used to prevent the flow of water. They run continuously from one end of the building to the other. Adjacent waterstops are joined with 3/4" soldered lap joints. Water stops are designed to accommodate movement by flexing. The recommended minimum weight for copper waterstops is 16 oz.

As cover plates are not required to stop the flow of water, their technical requirements are not as strict. The main criteria is that the material used must be strong enough to bridge the expansion space under given loads. Brass and bronze are used to provide the required strength.

11.3A. Building Expansion Joint at Concrete Floor

This detail shows a continuous cast-in-place copper waterstop bridging the space between concrete floor slabs.

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The detail also shows the use of brass or bronze cover plates. An insert is cast into the edge of each floor. The actual cover plates are then attached to one side of the insert and allowed to slide freely over the other side. This is also true for cover plates in the ceiling, as shown.

11.3B. Building Expansion Joint at Slab on Grade

In this detail, the grade slab is exposed to moisture from below. A continuous cast-in-place copper waterstop is used in the expansion joint to prevent water infiltration. A brass or bronze cover plate is shown in the floor slab, as described above.

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11.3C. Building Expansion Joint at Concrete Garage Floor Slab

Exterior concrete structures, such as garages, are exposed to a much greater volume of water. It is often impossible or impractical to completely prevent water from getting through an expansion joint. Under these circumstances, a copper gutter can be used to catch the water and direct it to a drain or spill. The gutter is supported by copper or bronze lock strips that allow it to accommodate expansion and contraction movement.

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