Bills of Quantities

TM 330 Lecture 5b

Preparation of Bills of Quantities

Introduction Most engineering projects employ Bill of

Quantities type of contract; Bills of Quantities are produced from

drawings; Drawings can be architectural; civil

engineering; structural engineering; geotechnical engineering; electrical; mechanical, chemical; etc.

Drawings must be detailed enough to be able to produce accurate and thorough Bills of Quantities;

Well prepared and accurate bills of quantities lead to well prepared tenders – do not leave the

contractor guessing; Easy evaluation of tenders; Smooth administration of the contract.

Nature of Bills

• Bills of Quantities comprise a list of items of work which are briefly described. The Bills also provide a measure of the extent of work and this allows the work to be priced. The work included in the item is defined in detail by the rules in the Method of Measurement. The item descriptions are therefore a shorthand to allow the relevant rules of the Method to be identified. The measure may be a single item or number, dimension (linear metre, square metre, cubic metre), time (hrs, weeks) or weight.

Definition - Bills of Quantities

• Definition:

– Bill of Quantities is a compiled list of items of work to be performed by the contractor;

– They describe the the works giving quantities and extent of work involved;

– These are referred to as item of work;

– Item of work are generally arranged in the BoQ in the order of their execution;

– BoQ items are separated to reflect the different trades that may be involved in the project;

– Example: for a building project, item may include:• Clear the site;

• Excavations;

• Cast of foundations;

• Construct the super structure;

• Erection of roof;

• Electrical wiring;

• Fix windows and doors;

• Finishes

• External works and clear the site.

Function of Bills• The Bills of Quantities may serve a number of functions

as:– A breakdown of the tendered price, with no contractual status,

but providing information for the selection from tenderers;– An estimate measure of the work for the tendered price, to be

used to arrive at a revised contract price once the actual quantities of work carried out are measured. This is the re-measure form of contract.

– A schedule of rates as the contract basis for valuing variations in the work.

– A basis for measure of the value of work completed for interim payments.

Functions of BoQ (cont).

• Contractors are asked to insert their prices against the work items;

• When summed up, together with other direct cost of supply of materials and machinery (PC Sums) and contingencies, they form the tender sum;

• The preparation of BoQ for building works is normally prepared by Quantity surveyors while that of civil engineering works is normally prepared by civil engineers;

• In a lot of cases, they work together.• In some special cases, other branches of engineering are

incorporated such as mechanical engineers, electrical engineers, service engineers etc.

Preparation of BoQ

• BoQs are normally prepared using standard rules referred to as standard methods of measurement;

• Building works are normally measured using the Standard Method of Measurement (SMM) for East Africa;

• For Civil Engineering works, standards such as the Civil Engineering Standard Method of Measurement (CESMM) can be used.

• The CESMM is published by the Institution f Civil Engineers, UK.

• We shall use this standard for the term project that we shall perform in this semester.

Process of Preparation of BoQ

• Enquiry: – A firm may be approached to prepare a BoQ for another firm

or it may arise from work that has been designed by the same firm;

• Assessment of Work Content: – It is necessary not only to assess the size of the task but also to appreciate

the aspects that may require other specilisations for accurate take-off; – It is to be appreciated that besides the design work (architectural, civil,

structural, etc), preparation of BoQ is most time demanding.

• Establish the type of Contract/form of tender documents: – The examination of the contract drawings and other specific project

features may lead to the consultant deciding on the form of contract to be used;

– Type of specifications, conditions of contract can also be determined at this stage; in any case, some key aspects of specs my already have been decided during design stage. Eg concrete grade 25; mild or high yield steel etc

Process of Preparation of BoQ (cont.)

• Resources Requirements and task allocations:– Human resources requirements – engineers; q/surveyors;

technicians; assistants; etc– Computer facilities and software;– Reproduction;– Need for sub-contracting.– Tasks are allocated to individuals or groups of individuals in

manageable portions; eg. earthworks; concrete works; walls; finishes; etc.

– It may be necessary to schedule the works such that resources such as drawings can be shared between the groups.

– It is often necessary to consult with each other and in particular the designers to obtain clarifications of details so that an accurate and detailed BoQ is achieved

Measuring Quantities – Taking-off

• All items are measured as accurately as possible to enable a fair price to be obtained;

• Various standard methods of measuring work items eg. SMM or CESMM;

• CESMM 2nd Edition contains classifications of work items Class A - Y

• Classifications include general items as well as specific work items.

• The BoQ should in principle contain all items described by drawings (or implied) and all other possible items that a contractor may have to perform to complete the works.

• If at the construction stage a contractor is necessitated to perform work that was not originally in the BoQ, a variation is normally issued.

• Frequent or excessive variations raise concerns from the client – either concerns for incompetence of the engineer or corruption!!

CESMM Classifications (2nd Ed)• Class A: General Items

• Class B: Ground Investigations

• Class C: Geotechnical and other Work Classifications

• Class D: Demolition and site Clearance

• Class E: Earthworks

• Class F: In situ Concrete

• Class G: Concrete Ancillaries

• Class H: Precast Concrete

• Class I: Pipe work - pipes

• Class J: Pipe work – fittings and and valves

• Class K: Pipe work – manholes and pipe wok ancillaries

• Class L: Pipe work – Support and protections etc

• Class M: Structural Metal work

• Class N: Miscellaneous metalwork

• Class O: Timber

• Class P: Piles

• Class Q: Piling Ancillaries

• Class R: Roads and and pavings

• Class S: Rails Track

• Class T: Tunnels

• Class U: Brickwork, blockwork and masonry

• Class V: Painting

• Class W: Water proofing

• Class X: Miscellaneous works

• Class Y: Sewer renovation and ancillary works

Extract from CESMM• Class F: In Situ Concrete

First Division Second Division Third Division

Provision of concrete

1.Ordinary Prescribed Mix m3

1 Grade C7.5 or 10

2 Grade C12.5

3 Grade C15

4 Grade C20

5 Grade C25

6 Grade C30

7 Grade C35

8 Grade C40

Cement BS12 or BS146

1 10 mm Aggregates

2 14 mm Aggregates

3 20mm Aggregates

4 40 mm Aggregates

Cement BS 4027 (Sulphate Resisting)

5 10 mm Aggregates

6 14 mm Aggregates

7 20 mm Aggregates

8 40 mm Aggregates

Provision of concrete

2.Ordinary Prescribed Mix m3

Sample Items• Items in this class in a BoQ format could be for example:

Code Description Unit Qty Unit Price

Amount

F156 Provision of ordinary prescribed concrete mix grade C25, sulphate resistant maximum aggregate size 14mm

m3 50

F413 Placing of mass concrete for blinding of thickness not exceeding 150mm

m3 50

F524 Reinforced concrete for footings thickness exceeding 500mm

m3 32

F663 Pre-stressed concrete for beams cross-sectional area between 0.1 –0.25m2

m3 29

Once all possible items have been measured, they are assembled together with other tender documents ready for the invitation of contractors to tender.

To be inserted by contractors

Methods of Preparing BoQs

• Three methods are used.• Traditional method

– Work from one drawing to the next taking of dimensions of items and recording them on continuous basis. Say from one floor of a building to the next.

– Using these sheets, information is assembled for similar items on another sheet of paper. Say all items related to Class F Concrete are assembled in another set of papers

– The actual quatities are then computed by ”squaring”.– For example: Concrete slab grade 25 2.7/3.5/0.25 means concrete

slab of size 2.7m by 3.5 m by 0.25 m thickness– Squaring is therefore

• 2.7x3.5x0.25 = 2.3625 m3

Cut and shuffle method

• This is a faster method than the traditional method. • The civil engineer or q/surveyor takes-off quantities

into specially designed sheets in duplicate where the original sheet is perforated into strips which can be separated from the book and collected together to form group of items.

• Squaring is done immediately on the same sheets. • The strips for similar items are put together and

handed over for billing.

Computer Aided Methods

• Computer aided systems can be based on simple database software or spreadsheets to sophisticated 4D software – xyz and time.

• Microsoft Excel Templates, Standard software such as those listed on http://www.bidshop.org/

• Some demo versions of these are freely available from the web.

• More sophisticated software are available.

Intelligent CAD systems• Normally, CAD system is only used as a platform for

preparing and presenting a model which has only geometrical and textural information of the design. The information contained in the model does not support all the activities involved in the engineering design, analyses and construction processes.

• An intelligent CAD is an integrated system which can not only represent the basic geometrical and textural information of an engineering object, but also other engineering properties useful to engineering design and analyses. The system should also be able to generate cost estimations, virtual walkthrough, and other analyses so that the whole project delivery procedure can be better supported.

• Advantages of an intelligent CAD system – Generation of photo-realistic image of designs before

the commencement of construction

– Automatic measurement of quantities and costs

– Conduct "what-if" analysis in order to reduce unnecessary design changes from clients

Intelligent CAD systems (cont.)

• Application in construction– Intelligent CAD systems are particularly useful to

Design-and-Build projects, as these systems allow design and design changes to be entertained efficiently

– Intelligent CAD systems can produce cost estimates in the form of a Bill of Quantities

– In combination with virtual reality technology, intelligent CAD systems can help users to conduct constructability analyses of designs so as to avoid impractical structures

Automatic measurement of quantities based on drawing recognition

• Taking off quantities is the most time consuming activity, as it requires the manual measurement of the dimensions and quantities of components such as steel reinforcement in a structure that is presented in the three perspectives of plan, elevation and cross section.

• A middle size project normally needs 4-5 person-months to take off the quantities. This amount of time increases exponentially with the size of project.

• In order to reduce the time and to improve the efficiency in quantity measurement, automatic measurement of quantities based on drawing recognition of 2D drawings is possible.

• Instead of manually taking-off and measuring quantities from engineering drawings, the system can automatically recognize drawing entities based on graphic representations and annotations in the drawings.

Advantages of Computer Aided Systems

• Productivity increased significantly• Better accuracy & consistency• Identification of partial discrepancies between

drawings

Arrangement of BoQ• Generally, BoQs are arranged in a similar format as the

CESMM or SMM;• For small projects the BoQ, and indeed all the tender

documents can be contained in a single volume.• In case the project has several large portions that can be

treated separately, separate BoQ Volumes can be prepared for the different sections;– For example;– BoQ 1: CoET Block A;– BoQ 2: CoEET Block B; etc

– BoQ N: External Works

Arrangement of BoQ for Building Works

• The arrangement of BoQ for building works generally involve the following items:– Preliminaries;– Substructure;– External walls;– External doors;– Windows;– Roofing;– Internal walls and partitioning;– Internal doors;– Finishing;

– Decorations;– Fittings and fixtures;– Plumbing and engineering installations;– Electrical power;– External works;– Provisional sums– Prime cost items;– Day works

Summary

• Well prepared BoQ gives contractors to submit well estimated tenders

• Contracts let on the basis of accurate estimates lead to smooth contract management

• All professionals are duty bound to ensure that BoQs and indeed all tender documents are prepared in the best possible manner so as to provide for opportunity for project success.

Thank you.