Job Book 9th Edition - Book - Page 223
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Stage 4 > Technical Design: Supplementary Material: 4/SM3
and economically worded, with the objective of transferring information from
designers to constructors with accuracy and certainty.
A specification can be prescriptive, in that there is precise description of the
materials, workmanship, etc. which leaves no area of choice to the tendering
contractor. It can also be written as performance requirements, either for the
building components or for engineering services, in which case there will remain
an area of choice on the part of the contractor as to how the stated performance
will be achieved. If performance specification is to be used, great care needs
to be taken in ensuring that the contractual terms recognise this additional
responsibility of the contractor. In reality, most modern specification sections
use a combination of performance and prescription.
Some architects’ practices might use a system of specification clauses developed
for use with particular types of work (e.g. housing refurbishment). Care must be
taken to keep such clauses relevant and up to date, and it is generally safer and
more convenient to adopt a well-developed system such as NBS. This allows for
consistent description of materials and workmanship (or systems, products and
execution) with full reference to British Standards and other codes and standards.
NBS also enables performance specifications to be developed.
NBS is available in electronic form as NBS Building and NBS Create (refer to
www.thenbs.com). These easy-to-use software packages enable the development
of specifications on screen, referring to guidance and other technical information,
such as British Standards. Some clauses require additional information that can
be typed in or completed by using drop-down ‘value’ lists of suggested solutions.
Under CPI the specification is the core document to which the other Technical
Design information refers. The description of materials and workmanship (or
systems, products and execution) contained in the specification should therefore
not be repeated on the drawing or in the bills – these documents should refer
to clause numbers in the specification. A specification will therefore be needed
even when there is a separate bill of quantities.
Where there is no bill of quantities, it may be wise to append a schedule of work
to the specification for pricing purposes, possibly supported by a schedule of
rates, or to require the tendering contractor to provide a priced activity schedule.
If the specification has been prepared using the CAWS system then a breakdown
according to work sections may not be very helpful when it comes to valuing
variations or certificates.
The architect as designer is responsible for the method of specification selected
and the content. Specification notes will normally be compiled during the design
process. The specification is a key document and will provide information to:
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