Bills Of Quantities (Senior Lecturer note)

BILLS OF QUANTITIES

The bills of quantities is a form of document which sets out the quantities and descriptions of the items of
labour, materials and plant required to erect and complete a building or other works in a systematic manner.
The preliminary section of the bill sets out the practical and contractual conditions of the project, particulars of
the type of contract to be used and also the details of general matters, which may affect the price of the work
together with project overheads. Project overheads are items that cannot be attributed to any particular
measured work section. The measured items are grouped in appropriate sections and each section starts with a number of preamble clauses.

CONTENTS OF THE BILLS OF QUANTITIES

The principal use of the bills of quantities is to obtain competitive tenders and for this purpose bills of quantities
should be prepared to a recognised Method of Measurement to standardise the bills.
Bills of quantities, prepared in accordance with a Standard Method of Measurement, fully describe and
accurately represent the works to be executed and this provides a uniform basis for competitive tendering.
During the construction of the project the client and the contractor use the bills as the basis for financial
management.
Bills of Quantities may consist some or all of the followings:
Bill Nr. 1. Preliminaries.
Bill Nr. 2. Preambles.
Bill Nr. 3. Measured Works
(a). Carcass - I. Foundations (Substructure)
ll. Frame (Columns & Beams)
lll. External & Internal Walls
lV. Partitions
V. Floors
Vl. Roofs
(b). Finishing - I. External & Internal Finishing (Walls, Floors & Ceilings)
II. Windows
III. Doors including openings without joinery
IV. Fixtures & Sundries
V. Stairs & Lifts
VI. Plumbing & Engineering Services
(c). External Works - I. Drainage
II. Roads, Paths, Site Layouts, Outbuildings etc.
(d). Spot Items - These items are alteration and repair items of a building.
Bill Nr. 4. Provisional Quantities
Bill Nr. 5. Prime Cost & Provisional Sums
Bill Nr. 6. Contingency Sums
Bill Nr. 7. General Summary
2
PURPOSES OF BILLS OF QUANTITIES
The bills of quantities are in use to the construction team for different purposes at different stages and it is used
in different ways. They are as follows:
To or by the Client
(a). The priced bills of quantities provide statistical information on project.
(b). A reasonable contract sum can be obtained through competitive tendering.
(c). It provides the basis for the preparation of cash flow during the construction.
To or by the Client’s/Consultant’s Quantity Surveyor
(a). Cost Analysis is prepared from priced bills of quantities and used to estimate the future projects.
(b). Priced bills of quantities used for Interim Valuation.
(c). Priced bills form the basis on which the final account is settled.
(d). Bill rates provide a good basis for valuing variations.
(e). Used for negotiating further contract. It may be a separate or a continuation contract.
To or by the Contractor or his Quantity Surveyor
(a). Provides a uniform basis for pricing of competitive tenders.
(b). Used to calculate the quantity of materials.
(c). Use for the preparation of the cash flow.
(d). Use to prepare the construction programme.
(e). Provides a good basis for the settlement of Domestic Sub-contractors’ claims.
To or by the Clerks of Works
(a). Use to control the quality of materials and standards of workmanship.
ESSENTIALS IN A GOOD QUANTITY SURVEYOR
The essentials in a good Quantity Surveyor are:
1. An ability to describe clearly, fully precisely the requirements of the Architect and arrange the bills of
quantities so that the builder’s estimator can quickly, easily, and accurately arrive at the estimated cost
of the project.
2. It is important that the Surveyor should be able to write clearly in language that will not be
misunderstood, and must have sound knowledge of building materials and construction, and of customs
prevailing in the industry.
3. The surveyor must be careful and accurate in making calculations, have systematic and orderly mind
and be able to visualise the drawings and details.
4. Requires a detailed knowledge of contractor’s prices, experience of the building process and an ability
to foresee the likely effect of economics trends to give Cost Analysis.
5. A certain amount of Legal knowledge (i.e. The Law of Contract) to deal with contracts.
3
PRODUCTION OF BILLS OF QUANTITIES
There are several techniques of preparing Bills of Quantities. The most important techniques in current use are
as follows:
(a). Traditional Method. (This method is also known as the Group System or London Method).
This system provides the “taker off” with a logical system of measurement designed to promote accurate and
efficient taking off. The work is measured in series of groups, each representing a particular section of the
building without regard to the order in which items will finally appear in the bill. As the sequence of
measurement is not related to the order of the bill the “working up” process must involve the preparation of an
abstract to collect and arrange the items in the order necessary for writing the draft bill. This system is mostly
used in the examinations.
(b). Billing Direct. (This method is also known as Trade-by-Trade System or Northern Method).
This method involves “taking off” by trades, in order of billing, without the necessity for an abstract and transfers
the measured items from the dimension sheets to the bill direct. Each item is taken off as a separate entity in
the order in which it will eventually be billed including all relevant deductions thereby reducing time and lowering
costs of preparing bills of quantities. This system is suitable when the work is relatively straightforward and the
number of items limited.
DIVISIONS OF BILL PREPARATION
There are several methods of preparing bills of quantities. The traditional method of preparation of bills of
quantities can be broken down into two main processes.
Taking off:
This involves the measurement of dimensions, scaled or read from the drawings and entered in a recognised
form of specially ruled paper called “Dimension Paper” and the composition of clear and concise description
sufficiently detailed to allow the accurate pricing of the works.
Working up:
This process can be divided into two stages as follows:
Squaring: This comprises squaring the dimensions and transferring the resultant lengths,
areas and volumes to the abstract.
Abstracting: The squared dimensions are arranged in convenient order for billing and
reduced to the recognised units of measurement.
The other processes are:
Editing: The editor must check and make adjustments in the abstract, prior to printing
as the draft bill is written direct from the abstract.
Writing the bill: This process involves the listing in full, the various items of work, making up
the complete project with the quantities involved in a suitable order, under work
sections or elemental headings.
QUANTITIES AS PART OF THE CONTRACT
When bills of quantities form part of the contract documents, the contract provides that the quantities of work
comprised in the contract, shall be that, set out in the bills of quantities. In such cases the builder is expected to
do and the employer to neither pay for more nor less than the quantities given, an arrangement, which is fair to
both parties. It will be seen how important accuracy is in the preparation of the bill, how a substantial error might
lead a building owner to enter into a contract which involved a sum considerably beyond what was
contemplated.
4
STANDARD METHOD OF MEASUREMENT (SMM)
The First Revision of the Method of Measurement of Building Works (Sri Lanka Standards 573:1999) sets
out rules for the measurement and description of building works. The SMM (SL) is a document, which provides
not only a uniform basis for measuring building work but also embodies the essentials of good practice. If all the
bills of quantities are prepared in accordance with these rules then all parties concerned are aware of what is
included and what is to be assumed. Without the use of such a set of rules, the quantities in the Bills of
Quantities can vary widely.
Sometimes in practice, it is more appropriate to depart from the rules in the SMM (SL), in which case this must
be stated in the description of the item. Generally it is stressed that the principles of measurement as laid down
in the SMM (SL) should be followed as the more deviations that take place then the less uniform a document is
provided, thereby creating possible uncertainty. Therefore, especially for examination purposes the use of the
SMM (SL) can be recommended.
REQUIREMENTS FOR ACCURACY
Whatever the method adopted for bill preparation, the requirement for accuracy is the same. For example:
1. Work shall be measured net as fixed in position overlaps. (General Rule 4.1)
2. Dimensions used in calculating quantities shall be taken to the nearest 10 mm. (i.e. 5 mm and less than
5 mm shall be disregarded). (General Rule 4.2). All dimensions shall be recorded to two decimal places
and waste calculations are to three decimal places.
3. Quantities measured in tonnes shall be given to two decimal places. (General Rule 4.3).
4. Other quantities shall be given in the nearest whole except that any quantity less than ten shall be given
as to the nearest first decimal. (General Rule 4.4).
5. Voids or openings, which are wholly within the boundaries of measured areas and voids or openings
wholly at the boundaries of measured piers, columns and similar members, shall always be the subject
of deduction, irrespective of size. (General Rule 4.5).
6. Items can be measured within a range of stated limits.
7. Minimum deductions for voids.
8. Averaging or an interpolation of levels may be required for the measurement of excavation.
Due to problems with reprographics and the inherent inaccuracy of the process, scaling drawings should be
avoided whenever possible. However, where dimensions are stated on drawings, there is no excuse for
measurements being anything other than correct. A bill of quantities shall be as accurate as reflection of the
drawings and information available at the time of measurement as possible.
QUALITY CONTROL
In the context of bills of quantities, under most form of building contract any error is not at the risk of the
tenderer but will be deemed a variation and liable for adjustment in the final account. Therefore, there is an
obligation to ensure that the bills of quantities are as accurate as possible by applying checks on both the
process and procedure in an effort to avoid or correct errors at the appropriate stage.
Check list.
1. Create a drawing register for each project to ensure that only the latest revised drawings are used. A
complete list of these drawings shall be incorporated in the preliminaries and shall form a part of the
tender document.
2. Check that there is sufficient information for taking off process. If not make use of Query Sheets, which
should be sent to Architect/Engineer in duplicate, for reply, with a copy kept in file.
3. Scales on drawings and the sum of internal and external dimensions shall be arithmetically checked.
5
4. Any separate schedules and/or specification notes shall be compared with annotations on the drawings
and especially with regard to references and the number of items.
5. Check the general information to be included in the Preliminaries.
6. The name of the project must appear on every sheet, which shall also be numbered and dated.
7. Offer the taking-off in a clear, un-cramped presentation and write the dimensions so as to avoid
introducing errors:
(a). A taking off list is essential with items being marked through once they have been measured.
(b). Annotate everything for clarity and make side notes for ease of reference and always use
figured dimensions in preference to scaling.
(c). All sundry calculations shall be calculated in waste so that the arithmetic can be checked and
others can follow the taking-off. Mental calculations cannot be checked.
(d). Dimensions shall never be erased, obliterated or altered. To correct dimensions neatly cross
them out, write NIL alongside, taking care to identify clearly the extent of the correction and rewrite
correctly.
(e). All figures must be clearly written in the correct column.
(f). To avoid repetition of dimensions, use is made of the timesing column whereby they can be
multiplied. Great care must be taken when timesing or dotting on so as to prevent squaring
errors, particularly when dealing with fractions. When writing fractions in the timesing column,
a horizontal line rather than a diagonal slash must be used to avoid any confusion with
timesing.
(g). When an item or dimension is to be deducted it must be prefaced with the word Deduct
(abbreviated Ddt.) and also subsequent deductions are marked similarly. The item or
dimension immediately following the deduction shall be preferred with the word Add.
(h). Do not use ditto at the head of a new page or the head of a column.
(j). Centre lines used for a number of related items shall be checked carefully.
(k). Rough arithmetical checks shall be made on the overall quantities, which are interrelated.
(l). Read dimensions through for any obvious errors before offering them up for squaring and the
person who squares the dimensions shall first check waste calculations to ensure that in the
transfer of totals to the dimension column no errors have occurred. If an error is found it shall
be referred to the taker-off prior to adjustment.
(m). Preamble details shall be checked and any outdated or obsolete references amended. When
measured work, specifically refer to a particular Preamble Clause, it shall be checked that they
relate to the correct item.
(n). Careful reading over and a final editing of the typed draft bill by an experienced Quantity
Surveyor will provide the last opportunity for corrections prior to printing and may reveal errors
which have missed in the earlier checks.
Differences of techniques between individual practices or Surveyors shall not be assumed as errors.
Contrasting circumstances and differing customs mean that not every eventuality can be anticipated.