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Jointed Bay


A jointed bay is a pour divided into smaller panels by sawn restrained-movement joints.

Technical Information

Depending on the method of construction, the size of a jointed bay is only limited by how much concrete can be placed in one session. As it is made up of many smaller panels, the aspect ratio of the formed bay is not of concern.

Induced restrained-movement joints are typically created in a maximum 6mx6m grid throughout a jointed bay. These dimensions are considered ideal to economically allow the slab flexibility for shrinkage and limit the risk of mid-panel cracking. The joints are typically installed at 3mm wide and generally are expected to open another 1-2mm on top of that.  Sawn restrained-movement joints require filling with a suitable sealant to support the arrises.

Formed free-movement joints provide the perimeter of a jointed bay and usually open up around 20mm, though this is wholly dependent on the size of the bay. Isolation joints are used around columns and at the edges of the floor, reducing restraint in the slab and the risk of random, uncontrolled cracking.

Jointed bays are typically only used for ground supported slabs. The use of a pile support would normally necessitate the use of fibre reinforcement, which doesn’t allow the use of induced restrained-movement joints.


  1. The Concrete Society: Technical Report 34; 11.1.1.


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