A waterstop is a pre-molded sealant that is applied across concrete joints to stop the passage of water where hydrostatic pressure exists. They are typically used for two types of joints:

1. Working joints: Joints where significant movement is expected.

2. Non-working joints: Joints where little or no movement is expected.


Most waterstops are provided in 6-inch, 9-inch or 12-inch widths. The type and shape of the waterstop should be based on the specific requirements of the existing joints. Common waterstops are manufactured from:

• Polyvinyl chloride (PVC).

• Styrene butadiene rubber (SBR).

• Neoprene.

• Metal.

In addition to the waterstops, the other application components include:

1. Backer rod (07910): Closed-cell polyethylene foam that has a diameter 25 percent greater than the joint width.

2. Sealant (07920):Sealant must be compatible with the joint filler.

• ASTM C 920: Polysulfide, polyurethane or silicone.

• Type S or M (one part or multi-component).

• Grade P or NS (pourable or non-sag).


Waterstops should be applied in accordance with the manufacturer’s requirements.

Working joints: Use a compatible waterstop that allows for concrete movement in both parallel and perpendicular directions.

Non-working joints: Use a dumbbell or flat, serrated waterstop. The dumbbell shape holds the waterstop in place and improves watertightness by providing a longer path for water to tunnel across the joint.

Sealant: For joints of ½ inch in width, the depth should equal the width of the joint. For joints of ½ inch in depth, joint widths should be ½ an inch to 1 inch. The sealant should not bond to the joint filler.