How do you accurately determine the duration of a work package when preparing BOQ?

It is very important that bills of quantities are prepared according to a standard, widely recognised methodology. This helps avoid any ambiguities or misunderstandings and so helps avoid disputes arising through different interpretations of what has been priced. In the UK, bills of quantities for general construction works were until most commonly prepared in accordance with the Standard Method of Measurement, currently in its7th Edition (SMM7). However, a new standard, the New Rules of Measurement became operative on1 January2013 and replacedSMM7 on1st July2013.

NB Other methods of measurement are used for civil engineering works (Civil Engingineering Method of Measurement) currently in its3rd Edition (CESMM).

SMM7 adopted the Common Arrangement of Work Sections (CAWS), a standard method for categorising the works. This is also the categorisation of work that is used for the National Building Specification (nbs):

• A - Preliminaries and general conditions.

• B - Complete buildings, structures and units.

• C - Existing site, buildings and services.

• D - Groundwork.

• E - In situ concrete and large precast concrete.

• F - Masonry.

• G - Structural carcassing, metal and timber.

• H - Cladding and covering.

• J - Waterproofing.

• K - Linings, sheathing and dry partitioning.

• L - Windows, doors and stairs.

• M - Surface finishes.

• N - Furniture and equipment.

• P - Building fabric sundries.

• Q - Paving, planting, fencing and site furniture.

• R - Disposal systems.

• S - Piped supply systems.

• T - Mechanical heating, cooling and refrigeration systems.

• U - Ventilation and air conditioning systems.

• V - Electrical systems.

• W - Communications, security, safety and protection systems.

• X - Transport systems.

• Y - General engineering services.

• Z - Building fabric reference specification.

However, this system is currently undergoing considerable change, with CAWS being incorporated into Uniclass, and Uniclass being replaced with Uniclass2 (see Uniclass for more information). In addition, NRM has moved away from the Common Arrangement of Work Sections (CAWS) to adopt its own system of indexing (see NRM2 for more information).

Bills of quantities can be prepared elementally or in works packages, by a process of 'taking off' which involves identifying elements of construction works that can be measured and priced. SeeTaking off for more information.

Bills of quantities are most useful to the contractor when they are prepared in work sections that reflect likely sub-contract packages. This makes it easier for the contractor to obtain prices fromsub-contractors and is more likely to result in an accurate and competitive price.

The bill of quantities should identify the different kinds of work required, but should not specify them as this can lead to confusion between information in the bill of quantities and information in the specification itself.

Disputes can occur where there is discrepancy between the bill of quantities and the rest of thetender documents (for example where an item is included in the drawings and specification but not in the bill of quantities), or where there has been an arithmetical error. Generally the priced bill of quantities will take precedent, and the client will be responsible for their own errors or omissions, which may be classified as relevant events (or compensation events) giving rise toclaims for an extension of time and loss and expense. However if an ambiguity or error is noticed by the contractor during the tender process, it is best practice for them to tell the client, even if there may be some commercial advantage to them not doing so.

Increasingly, software packages are available to assist in the preparation of preparation of bills of quantities, and building information modelling systems can be used to produce bills of quantitiesfrom information already contained within the model.

Bills of quantities are normally only prepared on larger projects. On smaller projects, or for alteration work the contractor can be expected to measure their own quantities from drawingsand schedules of work. Schedules of work are 'without quantities' instructional lists that allow thecontractor to identify significant work and materials that will be needed to complete the works and to calculate the quantities that will be required.

Approximate bill of quantities

An approximate bill of quantities (or notional bill of quantities) can be used on projects where it is not possible to prepare a firm bill of quantities at the time of tendering, for example if the design is relatively complete, but exact quantities are not yet known. However this will tend to result in more variations during construction and so less price certainty when the investment decision is made.

Some contracts allows for re-measurement of approximate quantities (for example, this is common on cut and fill on roadworks). Here, quantities are simply revised and payments made accordingly without the need to instruct a variation.

If an approximate quantity turns out not to have been a realistic estimate of the quantity actually required, this may constitute a relevant event giving rise to claims for an extension of time andloss and expense.

Approximate bills of quantities can also be used during the design process as a tool for controlling design. They are then sometimes included in the tender documents as a guide with a caveat stating that responsibility for measuring quantities lies with the contractor, and drawingsand specifications take priority over any description in the approximate bills (see Approximate quantities cost plan).

Duration of work package can be determine if we could breakdown the package in to a series of events or job. Each job must have a time frame or duration depending on company's productivity rate. For this reason quantity surveyor must provide a descriptive BOQ that  will describe a the package clearly. 

Scope / Standard Production Rates = Duration.