Construction Joints and Raft Foundations

I am sorry to say that even the simplest reply to your question is quite long. Your question is too vague and shows that you really need to go and read up a little.

The best book to buy on foundations generally is Tomlinson (google "tomlinson foundations"). Otherwise you need to google your question to find some university courses that can help explain.

Factors affecting your question:

• temperature differentials
• ground conditions
• finishes
• construction type (above ground and below ground)
• where you are building in the world

The major effects are:

1. differential movement or settlement

2. Loading/stress level on either part of the raft.

3. ingress of water across the joint which may lead to corrossion of rebars.

4. slide/shear failure across the joint

The precations are:

Detail the joint with a well designed shear key.

Provide water stop, preferably two if raft is thick enough like 4 feet.

Detail/design the joint plane for probable slip across the joint.

Akhtar Naviwala