The invention provides a void former (10) having a spacer region (16) for spacing adjacent void formers to form channels between them. The invention further provides a spacer accessory for a void former, the accessory having a spacer region for spacing adjacent void formers to form channels between them. Yet further, the invention provides a water tolerant void former for use in contact with water containing settable compositions. The invention also provides a cover for a void former, which cover may include the spacer region and may be water tolerant, permitting reuse of the void formers with which it is used. Finally, the invention provides methods of using the void former, accessory and cover in the construction of a settable composition slab.
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