Does a waffle slab need control joints?

Generally, standard residential waffle slabs are engineered as a single continuous structural unit and typically don’t use control joints the way a driveway or path does — the ribbed beam structure itself is part of how the design manages shrinkage behaviour.

Where a waffle slab is genuinely very large, or your specific design has particular requirements, your engineer determines whether any joints are needed as part of the overall structural design.

This is a genuine engineering decision specific to your slab’s design, not a standard feature automatically included the way it is for driveway or path concrete.

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