6191 Ancillary items (4) 6192 Substrate preparation (16) Preparation of the base surface to provide a suitable substrate for flooring; thin sheets of manufactured timber boarding, fibre cement, etc., secured mechanically or by adhesive; underlays of resilient surfacing to reduce transmission of sound from floor to floor surface and through the substrate; underlays to insulate the surfacing from cold substrate; underlays to increase the overall fire-resistance of the floor 6193 Surface finishes to concrete (32) Surface finishes produced by working the surface of concrete 6197 Cleaning, repairing and renovating existing trowelled and sprayed finishes (4) Cleaning, repairing and renovating existing trowelled and sprayed finishes 6198 Alteration work; removing and reconstructing trowelled and sprayed finishes (0) Demolishing and reconstructing trowelled and sprayed finishes as part of general demolition, reconstruction, alterations and additions