True or False: The isolation joint depth statement that it should extend to one-quarter depth is false.

True or False: The isolation joint depth statement that it should extend to one-quarter depth is false.

• A. True
• B. False
• C. Cannot determine
• D. Not sure

Answer: (B)

In concrete flatwork, isolation (expansion) joints are meant to allow movement between slabs or between a slab and a structure without transmitting stresses. To do this effectively, they should run the full thickness of the slab (and often into the subbase) so there is a true, continuous separation. A depth of one-quarter of the slab is typical for contraction or control joints, which are designed to create a deliberate weak plane for cracking to occur in a controlled location. If an isolation joint were only a quarter deep, it wouldn’t provide full separation or accommodate movement properly. That’s why the statement is false.

In concrete flatwork, isolation (expansion) joints are meant to allow movement between slabs or between a slab and a structure without transmitting stresses. To do this effectively, they should run the full thickness of the slab (and often into the subbase) so there is a true, continuous separation. A depth of one-quarter of the slab is typical for contraction or control joints, which are designed to create a deliberate weak plane for cracking to occur in a controlled location. If an isolation joint were only a quarter deep, it wouldn’t provide full separation or accommodate movement properly. That’s why the statement is false.