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A. The screed should not be laid until the concrete slab has been allowed to fully 'cure'. Curing time varies depending on ambient conditions and slab thickness but is normally at least six weeks. The cement screed will also require a period of at least three weeks to dry before tiling.

The only exception is where the flooring is fixed by the separating layer method. If a separating layer, such as a membrane, is laid directly over the structural floor, the six-week period may be reduced.

The work should be planned and carried out in consultation with those responsible for each of the trades concerned.

(Source: BS 5385 Code of Practice for the Design and Installation of Terrazzo Tile and Slab, Natural Stone and Composition Block Floorings)

Q. We are preparing a preliminary questionnaire for a foreign project, which includes a 'Prime Cost' items section. The documents received do not include a definition of the term Prime Cost. Can you help?

A. There are several definitions of the term in different text books. In view of this, many clients specify their own definition of 'Prime Cost' in contract documentation. For your information, here is our version: "Prime Cost: When used in bills of quantities and specifications, prime cost means that part of an estimate for work or supply of materials to be provided by nominated sub-contractors or suppliers. Prime Cost sums are determined by the client's advisers and detailed in the tender documents. The contractor may also be invited to execute work by a PC sum in certain instances."

(Source: Code of Estimating Practice, Sixth Edition, Chartered Institute of ÐÇ¿Õ´«Ã½, 1997)

Q. Does 'dredging' come under the Housing Grants, Construction and Regeneration Act 1996? We are dredging a lake to improve its environment as part of a pollution control project.

A.The above Act provides a procedure that, in the event of any dispute, allows the resolution method of adjudication to be used. On the basis of the information you have provided, 'dredging' and the work being undertaken would fall within sections 105 (b) and (e) of the Act. These sections state that: "Construction, alteration, repair, maintenance, extension, demolition or dismantling of any works forming, or to form, part of the land, including (without prejudice to the foregoing) ...inland waterways, pipe-lines, reservoirs, water-mains, sewers, industrial plant and installations for purposes of land drainage, coast protection or defence; "Operations which form an integral part of, or are preparatory to, or are for rendering complete, such operations as are previously described in this subsection, including site clearance, earth-moving; excavation; tunnelling and boring; laying of foundations. Erection, maintenance or dismantling of scaffolding, site restoration, landscaping and the provision of roadways and other access works."

Both parts of the section would need to be read together.

For any documentary evidence on this, independent legal advice would have to be sought from experienced construction experts.

CIOB would like to thank Tony Bingham, 3 Paper ÐÇ¿Õ´«Ã½s, London, for his assistance