Civil Engineering Project Management (4th Edition)

Measurement and bills of quantities 183
contractor a false impression of the nature of the work. It needs to be borne in
mind that sometimes it is the practice to ‘agree bill quantity’ for an item for
payment if there is no obviously large variation from what the drawings show.
Hence quantities should represent a best estimate of what will occur, in order
to be fair to both contractor and employer.
The problem of rock. A problem occurs when billing rock which may be
suspected but whose incidence is not known – as in the case of a long pipeline
where it is impracticable to sink enough borings in advance to discover the
depth and extent of rock everywhere. Sometimes a provisional quantity is put
in for rock, but if the extent of rock is not known, the problem is to decide what
provisional quantity is to be put in the bill? Also how can the tenderer price
such an item when the actual quantity to be encountered is only ‘provisional’.
Instead, it is suggested, a provisional sum should be included in the bill for rock
excavation, and a price for excavating rock should be agreed with the contractor,
if rock is encountered.
However, a consequent problem is that, if rock is encountered, it will almost
certainly delay the work, so the contractor will put in a delay claim. Despite
this, there is much to be said for negotiating a rate when rock is encountered,
because widely different methods – and therefore costs per unit excavated –
will apply according to the nature and direction of bedding of the rock encountered
(see Section 15.7).
Provisional quantities for other matters should likewise only be used with
care. They should relate to something known to be required, the quantity
being a reasonable judgement as to what might be required. This could apply
to such matters as bedding pipes on soft material, or bedding and haunching
pipes in concrete, or fully surrounding pipes in concrete where the actual
extent of such work depends on the site conditions encountered.
15.6 Billing of quantities for building work
Quite complicated buildings often form part of a civil engineering project, for
example power station buildings, pumping stations, stores, administrative
offices or laboratories. The CESMM gives units of measurement for some
common building operations, but the nature of building work is so diverse that,
in practice, many more items than shown in CESMM will be found necessary.
The CESMM will usually be found suitable for billing all work required to
complete the framework, walling, cladding and roofing to buildings, and such
matters as pipework, roads, sewerage, landscaping and fencing. Other building
items primarily cover the interior finishes, carpentry and joinery, and other
miscellaneous matters. These can be measured by some simple method a civil
contractor will understand, since he will have experience of building work as
well as civil engineering. It is not necessary to follow all the details of the standard
method of measuring building work, for example the many ‘extra overs’
listed in that method for brickwork. The preamble to the bills of quantities