Water Leaking in Precast Double Tees

[KimWT]

Hi!

It was rare to use pre-topped double tees in my region.
Recently, I heard some roof double tees water leak where 2" CIP topping concrete and
4" precast concrete meet in the flange.
When I worked in the North where most double tees were pre-topped,
I did not hear this problem.

Is this problem common only in the South where most double tees are field-topped?
What causes this problem?

Thanks!

 

[BridgeSmith]

If any movement occurs at the joint in the precast, the topping can crack and allow water through the joint. I assume the "pre-topped" sections had a continuous seal between the sections at the top surface. Even if the field-topped sections have a seal, it will be below the topping. Never underestimate the ability of water to find its way through anything, even with only 2" of head pressure.