chapter 2 - bill of quantity and specification

8/12/2019 Chapter 2 - Bill of Quantity and Specification

http://slidepdf.com/reader/full/chapter-2-bill-of-quantity-and-specification 1/18

Construction Contract Administration and Project Management (CON4371)

Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

Chapter 2

Preparation of Bills of Quantities and the use of Specifications

1.

Bill of Quantities for Civil Engineering Work

‐ This type of contract incorporates a bill of quantities to be priced by the

contractor and is one of most commonly used form of contract for civil

engineering work.

‐ A bill of quantities is prepared in accordance with the CESMM, giving as

accurately as possible the quantities of each item of work to be

executed,

and

the

contractor

enters

a

unit

rate

against

each

item

of

work.

Quantity x Unit Rate = $Tender Total

‐ Item description only identifies work whose nature and extent is

defined by the contract documents as a whole, including the Drawings,

Specification and Conditions of Contract.

‐ This encourage the complete design of work prior to tender and the

cost of civil engineering work frequently depends extensively on the

shape and location of the work, and the terrain. This information is best

extracted from

the

drawings.

‐

The use of bill of quantities offers the following advantages:

(a) It enables all contractors tendering for a contractor to price on exactly

the same information. The use of bill of quantities avoids the need for

all the tenderers to measure the quantities themselves before preparing

the estimate. If all tenderers have to measure the works, there is a

wasteful duplication of efforts and increase in the contractors’ overhead,

which will

eventually

be

passed

to

the

employers/clients.

(b) The bill of quantities is prepared in accordance with the Standard

method of Measurement, ensuring that tendering contractors have a

clear conception of the work involved.

(c) The contractor is paid for the actual amount of work done and thus

limits the risk borne by the contractor.

(d) While providing a fair basis for payment, it also provides a basis for the

valuation of variations, which occur during the progress of the work.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

2. Contents in the Bill of Quantities

There are various forms in which bills of quantities can be prepared, but no

matter which

format

is

used;

there

will

be

certain

aspects,

which

are

common to all types.

All bills will contain the following sections: ‐

• Preliminaries

• Preambles

• Measured Work

• Prime cost and Provisional Sums

•

Daywork

Schedule

Preliminaries section

The preliminaries section usually placed at the beginning of the bill.

Preliminaries will provide:‐

• Particulars of the type of contract to be used and;

• Details of general matters, which may affect the price of the work.

The items are mainly comprised of three categories: ‐

(a)

Headings of

Clauses

contained

in

the

Conditions

of

Contract

for

example:

Obligation of the Contractor, Commencement of Work etc.

(b) Matters contained in Section 1 Part V of the CESMM for example: Site

Office, Hoarding, Protection for the Works, Site Photographs, etc.

(Refer to the Section 1 Preliminaries of the CESMM).

(c) Any specific matters not covered in (a) or (b) above but cover many

important financial matters which relate to the contract as a whole, and

are not confined to any particular work section, and the contractor is

given the

opportunity

to

price

them.

For example: the Client may require his own contractors to enter the site to

do renovation works during the progress of works and the Main Contractor

will have to allow for all cost and time implication in the Preliminaries item.

Preamble Section

The preamble in a civil engineering bill of quantities is to indicate

• To the tendering contractors whether methods of measurement other

than CESMM

have

been

used

for

any

parts

of

the

works

and;




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

2. Contents in the Bill of Quantities (cont’d)

• Whether any modifications have been made in applying CESMM to meet

special needs.

Example:‐

(i) CESMM requires that excavation in rock is measured separately but if

there is difficult in doing so, then the rule of measurement maybe modified

to include all measurement of excavation in natural soil.

(ii) A Preamble will be provided stating that the Contractor’s rates shall

include excavation in rock if they encountered rocks during the excavation

works. This method will place the risks on the Contractor but will simplify

the

measurement

process.

The following main points are usually included in a Preamble: ‐

a) Attention is directed to other parts of the contract documents in

addition to the bills

b) The bills are prepared in accordance with the CESMM, any special

method of measurement should be stated

c) Prices and rates inserted in the bills are full, inclusive of wastage,

overhead, profit and other sundry items

d) Items with no price inserted will be considered to be covered by

prices of

other

items

Measured Works Bill

• The measured work section of a bill of quantities set out in a systematic

manner, the quantities and full description of the item required to

construct and complete the work for example:‐

Description Quantity Unit of Measurement Unit Rate

R.C grade 30/20D in fdn 100 m3 $950/m3

• The

level

of

detail

at

which

the

work

is

described

and

measured

is

controlled by a set of measurement rules in the CESMM.

• The rate of $950/m3 is inserted by the Contractor as his price for doing

the reinforced concrete work.

Provisional Sums

Provisional sums are sums provided for items of works, which the

requirement is uncertain at the time of tender and the works shall only be

carried out

on

the

instruction

of

the

Engineer.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

2. Contents in the Bill of Quantities (cont’d)

• Examples

of

works

which

are

not

suitable

to

be

measured

at

the

bill

rates

are works which are labour intensive such as demolition.

• Daywork is the method of valuing work on the

(i) Time spent by operatives (Labour),

(ii) Materials used and

(iii) Plants employed,

(iv) Additional percentage allowance to cover Profit & Overhead.

•

Normally

a

list

of

various

types

of

labour,

material

and

plant

are

prepared

for which daywork rates or prices are to be inserted by the Tenderers.

3. Types of bills categorized by the accuracy of the quantities

Bill of Firm Quantities

• In the preparation of a firm bill of quantities, design must be completed

and drawings

must

be

full

and

details

available

for

measurement

prior

to

tender.

• The Engineer will measure the quantities from the finalised drawings and

thus the quantities should reflect the work in the drawings.

• The quantities are firm quantities and usually this kind of bill will form

part of the contract and the quantities should not be altered unless with

the Engineer’s instructions.

Bill of

Approximate

Quantities

• There are circumstances when the quantities in the bill are not firm but

approximate.

• In such cases, the designs or drawings are not completed but the bill of

approximate quantities is prepared for tendering purposes.

• The approximate quantities shall subject to a final remeasurement upon

finalization of design drawings.

Circumstances when to use this type of Bill:‐




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

3. Types of bills categorized by the accuracy of the quantities

a)

Where

time

is

the

essence

and

the

general

drawings

have

been

formulated, and the Employer wishes to select a contractor before the

detail drawings can be completed.

In this situation, it is probable that sufficient design information is

available to enable approximate quantities to be produced to form a

bill.

b) With work below ground, the available information is likely to be too

imprecise for the preparation of accurate quantities.

The

building

can

be

established

but

the

depth

of

foundations

and

extent

of soft areas will be uncertain.

c) Provisional quantities maybe included in a firm bill of quantities to

cover work that is uncertain in extent and is subject to remeasurement

where the work is carried out.

Excavating in rock, the removal of underground obstruction maybe

classified under this category.

4.

Formats of

Bills

Trade Bills

‐ This is a traditional method which arisen due to the way the

construction industry has conventionally been organised.

‐ The trade format groups similar items together to avoid repetition. The

work items are grouped according to trade works.

‐ The arrangement of the trades usually follows the order in the SMM.

For example:

‐

‐Excavator

‐Concretor

‐Drain layer

‐Brickwork and Masonry

Advantage

1. The subdivision of the BQ according to trades allowed the estimator to

quickly break up the BQ and send out sections to trade sub‐contractor

for separate

quotations.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

4. Formats of Bills (cont’d)

2.

More simple

to

prepare

as

there

is

less

working

up

process

and

less

repetition work

Disadvantage

1. Not very good for showing the cost of various element.

Elemental Bills

‐ Elemental bills are divided into elements that correspond to the

functional part of the building.

‐

The

elemental

bill

groups

similar

elements

together

for

ease

of

cost

planning.

‐ Hence; trades such as Excavator, Concretor, Drainlayer, Brickwork, etc

will be replaced by headings such as Foundation, Structural Frame,

Suspended Slabs, Bridge Structure, etc

‐ The principal objective is to secure a precise tendering by making the

location of the work more readily identifiable and to provide a closer

link to the cost plan.

Advantages

1. It will be easier to extract from the bills the total cost for an elemental

item thus facilitate the use of priced BQ for cost planning.

2. Estimating can be made more accurate as items are related to a

particular part of a project.

3. It provides more reliable information for the contractor in their project

management works

4. Help to simplify the works of the Engineer in preparation of interim

payment especially

stage

payment

Disadvantages

1. This type of bills need more time as it involves a considerable repetition

of billed items

2. Bills can be extremely large and bulky

3. Additional expenses due to the extra repetitive work




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

5. Other Type of Contract that is used in Civil Engineering

Schedule of Rates

• A

schedule

of

rates

is

similar

to

a bill

of

quantities

but

without

the

quantities.

• In other words, it consists of a list of items with full descriptions, units of

measurement and unit rates.

• This type of contract is normally suited for maintenance and repair work

where the extent and nature of the works may not be known until the work

is executed.

‐ Generally the contractor is required to insert the rates in the schedule

of

the

listed

items

of

works.

Description Unit of Measurement Unit Rate

R.C grade 30/20D in fdn m3 $950/m3

(inserted by the contractor)

OR

‐ The rates maybe predetermined by the Employer whereby the

contractor will then enter an addition or deduction percentage to the

listed rates.

Description Unit Unit Rate % Adjustment

R.C grade 30/20D in fdn m3 $800/m3 (+15%)

Advantage:

(1) The use of this type of contract is that work on site can commence well

before the completion of the design.

Disadvantages:

(1)

Total cost

of

the

work

is

not

known

at

the

time

of

tender.

(2) The total cost of a project is only calculated by measuring the work as it

proceeds on site and pricing at the appropriate rates in the schedule.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

6. Use of Specification

The specification is read in conjunction with drawings and a bill of

quantities to

supply

the

contractor

with

all

the

necessary

information

he

needs to submit a tender and to execute the works.

The main functions of the specification are to:

1) Describe fully the workmanship and materials required to carry out the

contract.

The specification lays down the quality of material, standard of

workmanship, testing methods and acceptance criteria for construction

work.

2) Avoids duplication of descriptive information as full descriptions

appear in a single document which is the specification.

On a construction job, the descriptions of items contained in the bills of

quantities should be

‐ as brief as possible and with frequent references to the specification

clauses.

3) Provide

details

of

not

included

in

the

Conditions

of

Contract

In addition to the above, the specification also contains details of any

special responsibilities of the contractor which are not covered by the

conditions of contract.

4) To supplement the information in the drawings

It is obviously not possible to show everything on the drawings, e.g. specific

details of the way materials are jointed or fixed, details of standard of

workmanship required

etc.

Nevertheless the information is important for pricing and for quality

control and so must be given in the Specification.

For a well written Specification, it is therefore important that:

i) The specification and drawings are complete but without excessive

duplication. Drawings and specification must not contradict each other.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

6. Use of Specification (cont’d)

ii) The specification writer must know what is required‐ this implies a good

knowledge of

construction

technology,

both

the

way

in

which

works

fit

together and of construction materials

iii) The information is presented clearly.

7. General Arrangement of Specification

(a) General Clauses

Most specifications for civil engineering work begin with a selection of

‘general

clauses’

which

relate

to

the

contract

as

a

whole

and

are

not

confined to any particular trade or works section. The nature and content

of these clauses will vary from project to project.

An example of a typical general clause is as follow: ‐.

Heading: General Requirements

• The works to be executed under this Contract are to be carried out in

accordance with the Conditions of Contract, Specification, Bill of Quantities

and Contract Drawings.

• If

in

construing

the

Contract,

there

shall

appear

to

be

any

inconsistency

between the Specification and Conditions of Contract, the Condition of

Contract shall prevail.

• This clause draws the Contractor’s attention to the requirements of all

the Contract Documents and emphasizes that the Conditions of Contract

have precedence over the other contract documents.

(b) Technical Material and Workmanship Clauses

The specification

clauses

are

normally

followed

by

materials

and

work

clauses, which are related to the various sections of work making up the

job.

Material Descriptions

Considerable care must be exercised in the drafting of a specification, to

prepare clauses, which are concise, complete, and free form ambiguity.

The following alternative methods of describing materials, or a

combination of

them,

can

be

used

in

a specification.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

7. General Arrangement of Specification (cont’d)

Methods of Describing Materials in Specification Clauses:‐

(1) A

full

description

of

the

material

is

given

with

details

of

desirable

and

undesirable characteristic and appropriate test requirements

(2) Relevant standard reference, together with details of type or class

required. The contractor can then refer to the specified standard

(3) Name of manufacturer, proprietary brand or source of supply stated

and the contractor can obtain further particulars from the manufacturer or

supplier.

(4) Provide the Prime Cost of the material with brief description of supply

and

delivery

of

a

certain

quantity

of

the

material

to

the

site.

For example: Prime Cost of to be $2500/m2 (supplied and delivered to site)

For example, a material description on brick: ‐

Material Description

Bricks Clay bricks

Name of manufacturer as approved by the Engineer

Or Source of Supply

Prime cost $500.00 per thousand, delivered to

site

Desirable characteristics Well burnt, hard, square, clean,

sound

Undesirable characteristic Free from cracks

Tests Minimum compressive strength

7.0 Mpa.

Workmanship clauses

Specification clauses

covering

constructional

work

and

workmanship

requirement are generally drafted in the imperative and should give a clear

and concise description of the character and extent of the work involved.

For example as in Clause 25:144(1):‐

Brickwork shall be flushed up with cement mortar to form a level and even

bed to receive horizontal damp proof course.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

8. Classification of Specification

(1) Standard

Specification

• These are specification devised by experts in their fields in the

government departments and consulting engineering firms and they are

accepted as authoritative by the construction industry.

• In Hong Kong, some particular authorities for eg. ASD, Housing

Authority, Civil Engineering Department has comprehensive standard

specification which will be issued for every project.

• These standard requirements establish a uniformity of administrative

procedures

and

quality

in

material

and

workmanship

for

constructing

their

projects.

(2) Particular Specification

• Standard specification is unable to provide all of the requirements

needed for a specific contract.

• To fill this gap, another set of specification called the particular

specifications are prepared by the specification writer for the specific

project.

• The

particular

specification

clauses

present

requirements

applicable

only

to that specific contract.

• This is often achieved by amending the standard specification by adding

to them, deleting from them, or modifying them.

• The combined use of the above two specifications enables the speedy

readiness of specification suitable to the project.

9. Types of Specification

1) Performance Specification

• Performance specifications are sometimes called End Product

Specifications or End Result Specifications.

• They specify standards and criteria, and the end results to be obtained.

• Performance specification does not normally prescribe dimensions,

materials or methods of manufacture, instead, the desired quality; function

and other

characteristics

of

the

product

are

specified.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

9. Types of Specification (cont’d)

• By specifying the performance requirements, it becomes the

responsibility of

the

contractor

to

select

the

materials

and

methods

to

achieve the end result.

Advantages:

(a) Some control of design passes to the contractor.

(b) Many new ideas are encouraged.

(c) New materials or component can be incorporated.

(d) Contractor uses methods or plant familiar to himself

(e)

Period

for

design

may

be

reduced

as

helpful

in

eliminating

lot

of

detailed instructions for construction procedures.

Disadvantages

(a) Comparison of tenders is less certain due to variation in contractors’

specification.

(b) Cost of project may await tenders, as Engineer’s guide prices may not

apply

2) Proprietary Specification

• It restricts products to be manufactured in accordance with a defined

method or system

• An Engineer will after many years in business, acquire first hand

knowledge on the performance of various products and items of

equipment.

• He utilises this knowledge to guide him in specifying projects. He will

specified certain

methods,

or

products

or

item

of

equipment

by

its

brand

name, manufacture.

• Sometimes, in order to avoid any chance of favouritism and minimise the

restriction on competition, the phrase “equal and approved” is used in the

Specification.

Advantages

a) The Engineer exercises maximum control

b) All

tenders

are

on

the

same

basis




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

9. Types of Specification (cont’d)

c) Cost of project based on the Engineer’s method or specified proprietary

system of

products

d) Ensure Engineer’s familiarity with the design

Disadvantages

(a) The specified method may not be familiarised by the Contractor

(b) Reduced the opportunity for other alternatives which may be more cost

effective

(c) There may be time where is it impossible or impractical to make an

exhaustive

study

within

the

design

period

to

draw

up

a

list

of

proprietary

system

3) Descriptive Specification

• Descriptive specifications are most common in civil engineering

construction works.

• This type of Specification will provide detailed description of required

materials and their properties without specifying brand names.

•

It

will

also

provide

construction

details

and

the

desired

quality

of

workmanship.

• Descriptive specifications are sometimes called Material and

Workmanship Specification.

Advantages

(a) Control can be imposed on both quality and performance

(b) Contractor can use material and equipment familiar to himself

(c) Common

basis

has

been

provided

for

comparison

of

tenders

Disadvantages

(a) Cost of project can be affected largely by the material or equipment

used by the Contractor

(b) Greater supervision is needed.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

10. Format of Specification for Material

In specifying for material, there are two formats which are in use:

1) Close Specification

• A close specification is one which the description of material is so

detailed that only one product can qualify for use.

• A specification provided by the Manufacturer is usually a closed

specification, or

• In cases whereby the contract has specified for materials to be provided

by Nominated Supplier is also a closed specification.

•

Its

purpose

is

to

ensure

that

only

construction

products

of

a

desired

quality are provided by the Contractor.

• However, close specification will reduce competition in prices.

2) Open Specification

• An open specification is worded in such a way that the products of

various Manufacturers are acceptable, provided that they can meet the

specified function and quality standards.

• It allows substitution by specifying materials followed by wordings such

as “approved

equal”.

• It is useful when cost savings is possible or when the availability of

material is uncertain.

• This type is usually often used in Government contracts where open

competition is preferred.

Sources of Writing for Specification Writing

Information for use in civil engineering specifications can be obtained from

a variety

of

sources.

The

principal

sources

of

information

are

as

described:

(1) Previous Specification

In the majority of cases, specification for past projects is used as a basis in

the preparation of a new specification for a job of similar type.

When looking for a previously prepared specification, one should be

selected to commensurate with the magnitude of the future project.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18

10. Format of Specification for Material (cont’d)

For example:

a concrete

specification

for

a dam

construction

would

not

be

appropriate to use for construction of a simple building.

The use of previous specification expedites the task of specification writing

but care must be taken to bring the specification clauses to date by the

incorporation of the latest developments and techniques for the work

concerned.

In

addition,

clauses

have

to

be

modified

to

suit

the

design,

construction

in

the current job. Generally, details which are not applicable are omitted and

to insert information on additional features.

(2) Contract Drawings

The draft contract drawings will be prepared in advance of the specification

and these will show the character and extent of the work.

The specification writer will extract a considerable amount of information

from the drawings and will work systematically through them when

compiling the

specification.

(3) Employer’s Requirement

The employer or client often lays down requirements in connection with

the project and these will probably need to be incorporated in the

specification.

Typical requirements of this kind are the programming of the works as to

provide for

completion

of

certain

sections

of

works,

taking

of

precautions

so as to minimize interference with existing facilities etc.

Requirements of this nature will be reflected in the General Clauses of the

specification and should be to notice of the contractors they may result in

increased cost.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18


(4) Site

Investigation

Some of the information inserted in a specification will arise from site

investigation such as information on soil conditions and water table level

and site clearance work.

The contractor should be supplied with any relevant information to reduce

the risks and the number of uncertain factors in his tender.

(5)

British

Standards

The use of British standard in the specification clause permits a

considerable reduction in the length of clauses relating to materials and

components and products.

It also eliminates the contractor from reading lengthy descriptive clauses in

the specification. The standards are prepared by the British Standards

Institution which is the approved body for the preparation of a national

standard covering methods for tests, terms, definitions, standards of

quality, of

performance,

dimensions

etc.

British Standards prescribe the recognised standards of quality and of a

great value in drafting specification as they reduce the amount of

descriptive works yet at the same time ensure a good quality product.

(6) Codes of Practice

Specification clauses sometimes refer to relevant codes of practice to

ensure good

standard

of

construction

and

workmanship

without

the

need

for lengthy specification clauses.

Codes of Practice cover design, construction and maintenance aspect. Their

contents are widely known and recognised as a mean to secure improved

standards of works in the respective field.




Chapter 2

___________________________________________________________________________________

___________________________________________________________________________________

©VTC2013 of 18


(7) Trade

Catalogues

When materials of proprietary brands are used in a job, reference is often

made to the manufacturers’ catalogues for specifying the necessary

information in the specification.

This procedure will shorten the length of the specification clause and at the

same time ensured the use of a specific material with which the Engineers

familiar and in which he has full confidence.