Jumpform Cold Joints

Figure 1: Jumpform silo (left) and a slipform silo (right)

Figure 2 below shows the difference between the verticle form lines and the horizontal form lines where the cold joints are located. The horizontal cold joints are intentional and part of the jumpform process.

Figure 2: Form line vs cold joint

A closer look at the cold joint (See figure 3) shows that water has two paths through the wall (shown in blue and red below). Water could seep through the cold joint until it makes contact with the waterstop in the center of the wall.

Regardless of which path the water takes, it is required to travel uphill either to clear the water stop (blue) or to come back up to the cold joint (red). Both of these options require the water to travel uphill without any back pressure, which is very unlikely to happen. This is what prevents moisture from penetrating the wall.

When the form is “topped off” with concrete, the surface roughness at this cold joint helps with concrete bonding of the next jump, as well as helps prevent water penetration.

Figure 3: Typical Jumpwall Section and waterstop detail.

Note: Upon customer request, different types of waterstop can be used.

Structural Integrity

Planned and prepared cold joints do not present structural issues. These types of joints have been engineered for decades not only in jumpform silo construction but in buildings, infrastructure and other concrete structures across different industries. With proper design based on engineering principles and codes, cold joints are watertight and structurally sound.

For questions or to learn more, please contact Hoffmann Inc.