Sunk slabs are slabs which are cast a certain depth (200 or 300 mm or any other depending on design) below normal floor level. This extra depth is used for placing pipes and utility ducts. And then space is filled with sand or other lightweight materials until the normal floor level. Sunk slabs are generally made in bathrooms, washrooms and wash areas where water and sewage pipes are to be taken out and the depth between the normal floor level and floor level of the sunk slab is where these pipes are placed.
Method of construction of a sunk slab
Uses of the sunk slab