Quantity Surveying Book

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UNESCO-NIGERIA TECHNICAL & VOCATIONAL EDUCATION

REVITALISATION PROJECT-PHASE II

YEAR 2- SE MESTER 2

THEORY

Version 1: December 2008

NATIONAL DIPLOMA IN QUANTITY SURVEYING

TENDERING AND ESTIMATING II

COURSE CODE: QUS 210

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TABLE OF CONTENTS

WEEK 1:

1.0 PRICING OF PRELIMINARIES I

1.1 What are Preliminary Items?

1.2 Estimating for Typical Preliminary Items

WEEK 2: 2.0 PRICING OF PRELIMINARIES II

WEEK 3: 3.0 PRELIMINARIES ANALYSIS WORKSHOP 3.1 Preliminary Bill

3.2 Class Workshop

WEEK 4:

4.0 PREPARATION OF TENDER

4.1 Decision to Tender

4.2 Collection of Information

4.3 Enquiries and Quotations

4.4 Visit to Site

4.5 Visit to Consultants Offices

4.6 Receipt of quotations

4.7 Planning and Mid Tender Review

4.8 Preparation Of The Estimate

4.9 Final Review

4.10 Action after Submitting a Tender

4.10.1 Action with a successful tender

4.10.2 Action with an Unsuccessful Tender

4.11 Factors in Pricing General and Special Attendance on Subcontractors

WEEK 5:

5.0 MAJOR FACTORS AFFECTING TENDER PRICE

5.1 Factors Affecting Tender Price

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WEEK 6:

6.0 PRICIPLES OF ANALYTICAL ESTIMATING

6.1 Elements of a Unit Rate

6.2 Calculation of Unit Rates

6.2.1 Materials

6.2.2 Plant

6.2.3 Overheads

6.2.4 Profit

WEEK 7:

7.0 BUILD-UP HOURLY RATE FOR PLANT & EQUIPMENT


7.2 Groundworks

7.2.1 Hand Excavation

7.3 Excavation using Mechanical Plant

7.4 Banksmen

7.5 Disposal of Excavated Material

7.6 Earthwork Support

WEEK 8:

8.0 BUILD-UP UNIT RATE FOR SURFACE EXCAVATION

8.1 Surface Excavation

8.2 Removal of Excavated Materials

WEEK 9:

9.0 BUILD-UP UNIT RATE FOR CONCRETE WORK I

9.1 Concrete Work

9.2 Reinforcement

9.3 Guide to Using this Student Learning Pack

9.4 Concrete Works

9.4.1 Site Mixed Concrete

9.4.2 Ready Mixed Concrete

9.5 Concrete Reinforcement

WEEK 10:

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10.0 BUILD-UP UNIT RATE FOR CONCRETE WORK II

9.6 Concrete Work


9.6.2 Ready-Mixed Concrete

9.8 Concrete Work

9.7 Reinforcement

WEEK 11:

11.0 BUILD UP UNIT RATES FOR REINFORCEMENT

11.1 Bar Reinforcement

WEEK 12: 12.0 BUILD-UP UNIT RATE FOR FORMWORK 12.1 Formwork

WEEK 13:

13.0 BUILD-UP UNIT RATE FOR ROOFING

13.1 Roofing

WEEK 14:

14.0 BUILD UP UNIT RATE FOR MASONRY


14.2 Masonry works

14.3 Fact and Figures

WEEK 15: 15.0 PRACTICE QUESTIONS FOR TUTORIAL CLASS 15.1 Questions

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Course: Tendering and Estimating II

Course Code: QUS 210

Contact Hours: 2hrs

Course Specification: Theoretical Content

General Objective for Week 1: Appreciate the Build-up for Preliminary

Items

WEEK 1: PRICING OF PRELIMINARIES I (1.0)

1.1 What are Preliminary Items?

Preliminary items are items of cost which do not relate to any particular work section and

usually listed in the first bill of quantities. Many estimators prefers to inserts a lump sum for

all the preliminaries usually worked out as a percentage of the total of the measured works. It

is good practice however to put a price to each of the item. The price quoted should read at

after careful consideration of each item as it applies to the particular job at hand e.g water for

the works. It will be pipe bone water readily available on site or water has to be transported to

site on trucks.

1.2 Estimating for Typical Preliminary Items

(1) Site Supervision: These include the salaries and allowances paid to the site agent or

engineer and the administrative staff on the site such as cashiers, clerks, time keepers,

material checkers, store controllers etc. when this staff are sent aways from the area in

which they normally work and this necessitate them having to leave away from their

usual place of residence for a period of time a subsistence allowance may have to be

added to cover the additional expenses they will incure e.g

site agent

salary / month = 10,000

Housing allowance = 8,000

Transport allowance = 2,500

20,500 = 20,500

Cashier

Salary / month = 5,000

Housing allowance = 4,000

Transport = 2,000

11,000 = 11,000

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Clerk


Housing = 1,600

Transport = 1,500

6,600 6,600

Store controller


Housing = 1,600

Transport = 1,500

6,600 = 6,600

Messenger

Salary / month


Housing = 800

Transport = 500

2300 = 2,300

47,000/month

Contract duration 12 month

Add 1 month before project and

Add 3 months for defect liability period

Total month 16

16 months x 47,000 = 752,000

Add 10% for insurance and I.T.F = 75,200

827,200

Add 25% for profit and overhead = 206,800

1,034,000

(2) Site Accommodation

The contractor is usually expected to provide and maintain temporary site

accommodation for

(i) Supervising consultant on site

(ii) Site agent and site staff

(iii) Hut for workmen

(iv) Storage, shed for materials, tools etc.

Pricing for these must cover the cost of:

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(a) Initial construction of accommodation

(b) Removal on completion and making good ground disturbed

(c) Maintenance of accommodation throughout duration of the project

(d) Furniture including ventilation and air conditioning

(e) Overhead and profit from these estimator must remove the resale value of

items are still useable at the end of the projects e.g

Site office

Initial construction cost

Architect office 7.5m2

Engineer office 7.5m2

Quantity Surveying 7.5m2

Site agent 7.5m2

General office 10m2

Contractors room 12m2

Rest room 2.5m2

54.5m2 55m2

Circulation space 10% 5.5m2

60.5m2

61m2

61m2 at 9,000 = 549,000

Less resale value of items (about 27%) 149,000

N400,000

Demolish and cart away from site including making good @ 500/m2 x 61m2

= 30,500

(3) Mechanical Plant

This include all mechanical plant not allocated to unit rate such as cranes, lift,

dumpers, hoist, tractor, generating set, drills, forklift etc. the contractor is expected to

allow for this items whether they are purchased specifically for the project or they are

already owned by the firm or they are to be hired for the period they are required on

the project. The usual thing is to allow for

(a) cost of transporting plant to site

(b) Hire rate for the period plant is on site

(c) Cost of maintenance on site

(d) Profit and overhead

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(3) Tools

This include items such as shovels, portable drills, wheel barrows, batch boxes, guage

etc. smaller tools such as hammer, trowel, plumb level, plumb lines, paint brushes etc.

that are associated with a particular trade are not aloe for, here. They are usually taken

care of in the tool allowance included in the all in-labour rate for such fields. If the

project is large enough to used up small tools such as paint brushes, sand papers etc.

then the cost of such are included in the unit rate for the items that required their use

in pricing consideration is given to the cost of purchasing of the tools less their resale

value.

(4) Scaffolding

The total height and the type of construction determined the amount and type of

scaffolding required for a project, the contractor may purchase scaffolding for use in

the work. Whatever they may be, in pricing consideration is usually given to the

following.

(a) Hire rate for the duration of the project

(b) Labour cost for erecting scaffolding on site

(c) Labour cost for adopting scaffolding for special uses

(d) Labour cost for dismantling scaffolding at the end of the project

(e) Transportation cost for bringing to site and removing from site all scaffolding

(f) Profit and overhead

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WEEK 2: PRICING OF PRELIMINARIES II

(6) Water For The Work

Water required for the project is provided in either of the two ways supply by water

tankers if the site is far from a source or pipe bone water. In pricing consideration is given

the following:

If the site is far from the source: Cost of water supply by water tanker. It may be

necessary to write out an approximate estimate of the quantity of water required for the

project from previous project, certain allowance can be made for concrete work 480

liters/m3

For Block work 350 liters/m2

Rendering 30 liters/m2

Workman hut 2000/day

Site accommodation 20,000/day

Based on these allowances total quantity of water can be estimated for the whole project

and priced at prevailing water tanker rate for that areas.

Cost of Temporary Storage:

This include

(a) Cost of labour and materials in constructing surface tank, overhead tank, pipe work

and its pumps.

(b) Cost of cleaning and maintaining tanks, water pipes and water pumps.

(c) Cost of removal of water storage and temporary pipe work and making good ground

disturbed

(d) Overheads and profits

(a) Pipe Bone Water:

Pricing will include

(i) Cost of water connection by water board

(ii) Cost of labour and material for laying pipes

(iii)Cost of temporary storage

(iv) Water rate are usually charged as flat rate per plot. Therefore no need to estimate

approximately

(v) Cost of disconnection, removal of pipe and making good defect

(vi) Overhead and profit

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(7) Lighting and Power for Work

As in the case of water, provision of power is effected in either of two ways

(a) Power generating set: If site is far from existing mains, pricing will include

(i) cost of hiring generating set for the duration of the project.

(ii) Cost of cables, wiring and light fittings

(iii) Cost of running and maintaining generating set for duration of project

(iv) Cost of labour and materials for constructing temporary sheds for generators

(v) Cost of dismantling shed, removal and making good

(vi) Cost of transporting generating set to site and removal on completion of project.

(vii) Overhead and profit

(b) Electrical supply from electrical authority mains, pricing will include

(i) Cost of connection to the electrical authority

(ii) Cost of cables, wiring and light fittings

(iii) Cost of electricity bills

(iv) Cost of disconnection on completion of project

(v) Cost of hiring a standby generator in case of electricity failure

(vi) Overhead and profit

(8) Temporary Road

In certain building and civil engineering construction, temporary road have to be

constructed from the existing road to the site in order to get access to and make

possible the distribution of materials to various part of the site. Temporary road may

also be required is first worked and priced with the following considerations

(a) Cost of labour during clearing the road

(b) Cost of excavation either by hand or by mechanical plant

(c) Cost of labour and materials in laying laterite, blinding, gravel

(d) Cost of maintaining the road for the duration of the project

(e) Cost of removal of temporary road if not required at completion of all works on

site and making good ground disturbed

(f) Overhead and profits

(9) Temporary Telephone

If the project requires the telephone, the constructor must arrange for telephone

communication to be installed on site for easy communication for the duration of the

contract, pricing will include

(a) Cost of telephone installation by telephone organization in this case NITEL

(b) Cost of telephone bills

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(c) Cost of maintenance

(d) Cost of disconnection\

(e) Overhead and profit

(10) Control of Traffic and the Additional Cost

Reconstruction and repairing of existing road, lying sewers, water mains etc. in

existing roads and construction works in congested areas may create the necessity for

closing part of some road temporarily to traffic. In such cases the provision of one

way traffic control, diversions and access to adjoining houses, shops etc. may become

necessary. The following should be given consideration

(a) control of traffic which involves

(i) Cost of speed breakers

(ii) Cost of constructing barriers

(iii) Cost of red flags

(iv) Cost of labour flagging traffic

(v) Cost of providing diversion

(vi) Cost of removal of sign board to adjoining house, shops, garage etc.

(b) The provision of access road to adjoining houses, shops, garages etc

(i) Cost of labour and materials to provide pedestrian and vehicular access to shops,

houses, cars and park etc.

(c) Additional cost of work on existing road where traffic is involved

(i) Cost of delays to progress of work due to traffic and congestion

(ii) The presence of existing water mains, cable sewers, culverts etc.

(iii) Watching and lighting the work

(iv) Overhead and profit

(11) Welfare and Safety of Work People

This will comprise the cost of

(a) First aid box

(b) Drugs, antiseptics, bandages etc.

(c) Providing a nurse or medical attendant

(d) Maintaining first aid box

(e) Removal

(f) Protective clothing such as overall, element, nose mask, face mask, ear plug, boot

eye shield (industrial goggle)

(g) Safety equipment such as hose, fire fighting equipment

(h) Overhead and profit

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(12) Temporary Fencing, Hoardings, Screeds, Fans Gantries and Similar Items.

Each will comprise the cost of

(a) Labour and materials

(b) Maintenance

(c) Removal and making good

(d) Overhead and profit

(13) SITE SECURITY:

This will comprise

(a) Cost of labour and materials to construct temporary security shed post

(b) Labour and materials to installed security lighting, intruder alarms

(c) Furniture, stationeries, tags, I.D card etc.

(d) Wages for workmen

(e) Hiring of watch dogs

(f) Removal of sheds and lightening on completion of project and making good ground

disturbed

(g) Overhead and profit

(14) Removing Rubbish and Site Clearance on Completion of Project.

This involves the cost of

(a) Labour and materials clearing off such rubbish.

(b) Plant, lorry and labour loading such lorry transporting the rubbish from site

(c) Labour and materials cleaning up door, windows etc.


(15) Site Meeting: this will Comprise the Cost of:

(a) Provision of stationeries at each meeting

(b) Provision of refreshment at each meeting

(c) Wages of attendant


(16) Setting out of the Work:

this will comprise the cost of

(a) Pegs, templates and ropes or line

(b) Hiring of theodolite, precise level and other survey equipment

(c) Bringing to site and removing from site all the above name equipment

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(d) Fees for engineer and the assign team

(e) Overhead and profit

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WEEK 3: PRELIMINARIES ANALYSIS WORKSHOP (3.0) 3.1 Preliminary Bill The preliminaries bill gives the contractors the opportunity to price overheads which is

described in the Code of Estimating Practice as the cost of administering a project and

providing general plant, site staff, facilities and site based services and other items not

included in bill rates.

Preliminaries costs vary from contract to contract depending on complexity of work, size of

contract, specialist plant and equipment required, conditions imposed by the employer etc.

On relatively simple contracts preliminary costs may be in the order of 10 15% of the

contract sum whereas on complex contracts this figure could be much higher.

A contractor must calculate the cost of the preliminary items separately for each contract, no

two contracts are the same.

SMM7 recommends that fixed and time-related charges should be identified separately in a

bill of quantities.

A fixed charge is defined as the cost of work which can be considered as being independent

of duration

A time-related charge is defined as the cost of work which is to be considered as dependant

on duration.

3.2 Class Workshop

The appendix below is a summary of the bill for the case study project. Students will be

expected to appreciate and be able to work out how preliminary items in the bill are priced

and distributed between time or cost related and fixed charges for the purpose of monthly

valuations.

Procedures:

The work book will be made available to students at the beginning of the lecture. Time will

be allowed for students to read and comprehend the notes. Students will then be asked to sit

in groups of between 3 and 4 to discuss their understanding and set up query list on the

project.

After about 30 minutes, each group will be required to use the preliminaries breakdown form

to identify percentage allocation of each preliminary item across the table and to provide

justification for the allocation on each item.

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Appendix 1 attached shows the tender submission details and actual progress achieved on site

for monthly valuation purposes on a typical construction project.

(a) Allocate the preliminaries to time related and lump sums sections (Use form

Appendix 2).

APPENDIX 1 TENDER SUBMISSION DETAILS

Bill No. Preliminaries

A Supervision 14,000.00

B Plant 1,200.00

C Scaffolding 1,200.00

D Welfare Facilities 2,100.00

E Site Huts 1,000.00

F Site Telephones 400.00

G Temporary Lighting & Power 400.00

H Programme 200.00

J Watching 1,250.00

K Site Hoarding 1,800.00

L Temporary Roads 950.00

M Setting Out 400.00

N Drying the Works 500.00

O Cleaning Away Rubbish 500.00

P Water for the Works 727.00

Q Insurance Against Injury to Person and Property 3,401.00

Total Bill No. 1 30,028.00

Bill No. 3 External Works

A Soiling and Seeding 4,082.16

B Paths and Pavings 6,111.27

C Retaining and Screen Walls 2,017.33

D Drainage 9,127.16

E Fencing 1,812.19

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Bill No. 2 Measured Work

A Demolition 1,200.00

B Excavation and Earthwork 11,526.16

C Concrete Work 29,526.41

D Brickwork and Blockwork 31,416.12

E Roofing 14,112.16

F Woodwork 35,516.44

G Plumbing and Mechanical Installations 18,642.12

H Electrical Installations 9,216.14

J Floor, Wall and Ceiling Finishings 17,316.18

K Glazing 4,127.13

L Painting and Decorating 12,011.14

184,610.00

Bill No. 4 Prime Cost Sums

Nominated Sub-Contractor

A Piling 8,500.00

B Profit 5% 425.00

C General Attendance Item 170.00

D Specialist Landscaping 27,000.00

E Profit 5% 1,350.00

F General attendance Item 600.00

Nominated Suppliers

G Kitchen Equipment 18,000.00

H Profit 5% 900.00

J Sanitary Fittings 12,000.00

K Profit 5% 600.00

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L Ironmongery 5,000.00

M Profit 5% 250.00

Statutory Undertakings

N Water Main Connection 1,200.00

O Profit 5% 60.00

P Gas Main Connection 500.00

Q Profit 5% 25.00

R Electrical Main Connection 5% 500.00

S Profit 5% 25.00

T Sewer Connection 1,400.00

U Profit 5% 70.00


Tender Summary

Bill No. 1 Preliminaries 30,028.00

Bill No. 2 Measured Work 184,610.00

Bill No. 3 External Work 23,150.11

Bill No. 4 Prime Cost and Provisional Sums 78,575.00

Bill No. 5 Daywork 9,050.00

TOTAL TENDER SUM 325,413.11

Bill No. 2

Item A complete

Item B complete

Item C complete

Item D complete

Item E complete

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Item F 50% complete

Item G 40% complete

Item H 40% complete

Item J 20% complete

Item L 10% complete

Bill No. 3

Item A 20% complete

Item B 20% complete

Item C 40% complete

Item D 40% complete

Bill No. 4

Item A complete

Item D 8,600

Item G 8,000

Item J 6,000

Item L 2,000

Item N complete

Item P complete

Item R complete

Bill No. 5

Variations 9,000.00 agreed.

Materials on Site 6,237 agreed.

The following AIs were received from the Architect in respect of the following Prime

Cost and Provisional Sums:

1. Accept a quotation of 10122.50 from Keane & Bonney Piling Ltd.

It was observed that the Piling nominated sub-contractor had erroneously left out the

main contractors discount in their quotation for the works.

Effect the necessary corrections before valuation.

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2. Accept a quotation of 27500.00 from Landson Landscape plc.

3. Accept a quoation of 19012.00 from Kitchen & Sons for the supply of kitchen fittings.

4. Accept a quoation of 13176.00 from Loo Ltd for the supply of sanitary fittings.

5. Accept a quoation of 8820.00 from Smith & Smith for the supply of ironmongery.

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APPENDIX 2

JCT 80

Breakdown of Preliminary Items

Cost

Related

Time

Related

Lump Sums Total

Start Finish

Supervisor

Plant

Welfare

Site Huts

Telephones

Temporary

Lighting and

power

Programme

Watching

Site Hoarding

Temp Roads

Setting Out

Drying the works

Cleaning Rubbish

Water

Insurance

TOTALS

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Questions:

(1) Define prelimiaries and give three examples of a prelimiary item

(2) How do contractors price these items?

(3) Define fixed costs and provide five examples of an item you think would be priced as a

fixed cost item

(4) Define time related costs and give five examples of preliminary items you think a

contractor would price as a time-related cost.

GENERAL OBJECTIVE FOR WEEK 4:

Know the tendering procedures.

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WEEK 4: PREPARATION OF TENDER (4.0)

Reference: CIOB (1997) Code of Estimating Practice, 6th Edition. Ascot: CIOB

The preparation of a tender can be divided into six stages.

4.1 Decision to Tender

The tender documents arrive and the estimator records all relevant information such as:

The time allowed for preparing the tender Drawings available The approximate value and extent of the project The client, Architect, Q.S and other consultant Value of main contractors own work Project Details eg phased work, conditions of contract, access to site, working conditions. Firm price or fluctuating price tender required Current workload and timetable for project After reviewing the above information, management must decide whether to tender for the

project or decline the invitation. If it is decided not to submit a price, the tender documents

should be returned immediately to the architect/supervising officer. If it is decided that a

tender should be submitted, the contractor move to the next stage.

4.2 Collection of Information

The time allowed for preparing a tender is always limited; the estimator must plan the

programme very carefully. The work which has to be undertaken in a typical 4 week tender

period comprises:

Despatching enquires Visit consultants offices Visit the site Receipt of quotations and examinations The mechanical process of pricing the tender documentation Meetings with plant manager, contracts manager etc to determine a preliminary

programme, construction methods and likely plant requirements.

4.3 Enquiries and Quotations

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Suppliers

Enquires should state:

The specification of the material The quantity required The anticipated delivery dates The terms upon which the price is required The date by which the quotation is required The address of the site and access details Period for which the quotation is open for acceptance

Sub-contractors

Photocopies of the relevant parts of the bill of quantities, specifications and if possible copies

of drawings, should be sent out to perspective sub-contractors. Enquires should state clearly:

The items to be priced The terms of the main contract The period for which the quotation is open for acceptance The plant, materials, attendance etc to be provided by the main contractor Anticipated commencement and completion dates The form of contract and details from the appendix The terms of payment Date by which the quotation is to be submitted Address and details of the site

4.4 Visit to Site

The visit to site can be made after all enquires have been despatched and before prices begin

to come back. The visit to the site will enable the estimator to produce a report giving the

following information:

The position of the site in relation to roads etc Names of local and statutory authorities Details of site/ground conditions, spot items etc Site access, egress and possible site layouts

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Facilities for disposal of surplus excavated materials etc

4.5 Visit to Consultants Offices

It may be that only drawings showing plans and elevations will be sent out with the tender

documents and that further details and working drawings can be examined at the consultants

offices e.g. the estimator may require further details of manufactured joinery, steelwork

joinery fittings etc, before these sections can be priced accurately.

4.6 Receipt of quotations

Prices received from sub-contractors and suppliers are examined for sufficiency, terms etc

4.7 Planning and Mid Tender Review

The project is discussed with other managers to determine a preliminary programme,

construction methods, sequence of work, site layouts and what other plant, services, labour

and site staff are required.

It must be decided whether:

All labour can be obtained locally or will it be necessary to recruit for the project. Sufficient plant is already owned or is it necessary to purchase/hire additional items. It would be desirable to sub-let any further work. The preliminary programme should also be prepared containing the following information:

Contract starting and completion dates Any work to be done in stages Work to be sub-let by main contractor Work to be done by nominated sub-contactors (if JCT 98 form)

4.8 Preparation Of The Estimate

It can be divided into 4 stages:

1. The establishment of all-in rates for key items i.e. labour, gang costs, plant costs etc.

2. The selection of domestic sub-contractors and suppliers

3. The use of these all-in rates together with costs per unit for materials to calculate unit

rates for each item in the bill

4. The pricing of the preliminaries and project overheads

4.9 Final Review

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The consideration of the estimate to produce a tender is the responsibility of management.

The estimator and other senior staff will prepare reports for consideration by management

who will consider the following items before determining the tender figure;

Project reports Conditions of contract Contractual and construction risks Terms of the quotations from sub-contractors Capital required for the project Technical and management staff required Current workload Market Conditions Competition Reputations of client, consultants and area.

Following evaluation of the alternatives, risk and scope for profitability the mark up is

determined and the actual tender figures calculated. The decision being made within the

framework of company policy.

A record of all tenders should be kept together will the results (if known) for future reference.

4.10 Action after Submitting a Tender

4.10.1 Action with a successful tender

Check contract documents to ensure that:

The dates, penalties etc are the same as those contained in the tender documents The bills have been copied correctly from the original The drawings are those which were circulated with the tender documents Disseminate information

Information should be made available to those responsible for purchasing, construction

planning and plant.

Feedback information

Feedback from site on labour and plant outputs etc, to be kept for future pricing

Cost/Value Reconciliation

At regular intervals during the construction period, the costs at that time should be compared

with a meaningful valuation of work done in order to check that the job is on target

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4.10.2 Action with an Unsuccessful Tender

It the tender has been unsuccessful the contractor must assess why this is the case. Records

of tenders submitted must be kept and estimators must evaluate their performance. Suppliers

and sub-contractors should be notified of results as soon as possible.

Factors in Pricing General and Special Attendance on Subcontractors Each site has its own peculiar characteristics which can have considerable influence on the

total cost of development. Some of the more important factors are:

(1) Location of site: - Due to higher wastages, materials and other cost, it is expensive to

erect a similar building in an urban area than in a provincial setting. Some parts of the

areas are subject to higher rainfall than others and this can lead to a greater loss of

working time even within the same region, the cost of operating on different sites can

vary widely. A project on a remote country site may involve long length of temporary

access road and temporary power cable for electricity supplies and increase cost of

transporting operatives and materials and components, protection of adjoining buildings

and the public and restrictions on the use of mechanical plant. Taking these problems will

incure additional cost. Furthermore, a very expose site may make working conditions

more difficult and costly. Some locations may be more vulnerable to vandalism and theft

and so require more costly protective measures.

(2) Demolition site clearance: A site may contain buildings which requires demolition, paved

areas which requires breaking up and trees which requires felling, grubbing up and

disposal of their roots, another site may be cleaned of all obstruction.

(3) Contours: Few sites are entirely level. The most steeply slopping, the more greater will

be the cost of foundation and earthwork, the steeping of strip foundation increase their

cost. Most buildings requires constant floor levels and this will involve considerable

excavation and fill on its slopping site.

(4) Ground conditions: Where the strata is low load bearing capacity. It may be necessary to

introduce pile or other more expensive types of foundation. Raft foundations on made up

ground or in areas liable to mining subsidence may be three trust as expensive as normal

strip foundations where as pile foundation used to convey loads to a deeper load bearing

strata could be as much as five times as expensive. The cost of excavation in rock could

be five to eight times as expensive as working in normal ground, the provably length of

haul in the disposal of surplus soil also needs consideration. Where ground water is close

to the surface of the site, costly pumping operations may be needed. A wet site may also

involve raising temporary sheds and offices on brick bases and more costly temporary

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roads. The types of strata will also influence the form and extent of timbering or other

means of supporting that will be needed to the sides of excavations.


Know factors affecting tender figures.

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WEEK 5: MAJOR FACTORS AFFECTING TENDER PRICE (5.0)

Construction cost is a broad phrase or term and can be interpreted to mean cost of any sort

to anyone associated with construction work. It depends on the point of view let us say you

are a contractor, your costs are your expenditure on labour, materials and plant. The clients

cost of land, consultant fees and so on.

The base cost of construction therefore comprises of expenditure on materials, labour and

plant, the quantities of materials, labour and plant required for a job are determined &

attaching prices to these defines the basic construction cost, but to these are also a variety of

factors that affect this basic cost: -

5.1 Factors Affecting Tender Price

(1) Market Condition:

The volume of work in progress in the area at a given point in time affect construction

cost. When the market is burying with many project, tender price list are generally high.

Most consultants are busy and competition is not keen. However during ausle times when

there are few projects, contractors are anxious to out bid themselves so as to stay in

business, so construction cost tends to be lower.

(2) Availability of Materials:

When required materials are readily available in an area where a project is to be executed,

materials will be cheaper than where they are not so available. Generally, materials are

cheaper where they are produced e.g if you can buy cement directly from Ashaka, the

price will be a lot cheaper than in Kaduna because of transportation and profit margins of

middlemen and so on. Imported materials for similar reasons are more expensive than

locally produced materials.

(3) Availability Of Labour:

Where a certain type of labour is not readily available in the area where a project is to be

constructed, it may be necessary to import from an area where such labour is available.

Some inducement may have to be offered before such labour will move from its base

such as transportation, accommodation, inconveniences allowances etc. these add to the

cost of construction.

29

(4) Transportation:

The farther a site is from town, the more expensive will be the construction cost e.g the

same building to be constructed in Barnawa and also near Kaduna Airport will cost

differently, the additional cost of transporting materials, labour and plants to the airport

site will increase the cost of construction.

(5) Location:

The standard of living in an area affects the cost of construction. People are willing to pay

higher prices for construction in places like Lagos and Abuja than are to pay in other

places like Benin, Kaduna or Enugu.

(6) Location of Site: -

The particular location of the site can have significant effect on cost. Remote site may

require additional cost for the provision or access roads and temporary services or the

provision of additional security measures. Also, a site in a congested or restricted area

also gives rise to major problems such as delivery & storage of materials and

components, protection of adjoining buildings and the public, restriction on the use of

mechanical plants and so on, all these will increase the cost of construction.

(7) Time Consideration: -

For certain reasons, a project may need to be completed in a very short time, this tends to

push up construction cost. Labourers may be required to work overtime and overtime

rates are usually higher than normal rates. Incentives scheme may have to be introduced

to increase labour productivity. Closure supervision is necessary as mistake must be

avoided, there may be time to apply remedial action.

(8) Site Condition:

May affect the construction cost of a particular building. The nature of ground may

necessitate more complex form of foundation. The ground water level when close to

surface will involve costly water pumping operation. A wet site may involve rising

temporary sheds and offices above ground level and they involve more costly temporary

roads. Steeply sloping site may involve major cost in cutting and filling requirements,

existence of buried pipes and cables may involve major cost to re-root such.

(9) Total Height of Building:

The higher a building is, the longer it takes and more difficult it is to get the point of

execution of works. It is also more difficult to work at such height. Labour charges for

30

working at great height are higher than abnormal height, there is also the cost of

providing additional safety measures and insurance. Also, the need for special

scaffolding, hoist, tower crane, elevators etc. will tend to increase the cost of very tall

building over the cost of building requiring the same quantities at ground level.

(10) Legislation:

Has a way of affecting construction cost in dramatics manner as we have seen in Nigeria

over the years e.g minimum wage, import restrictions and duties, labour policies, fiscal

policies such as exchange rates, interest rates etc. in for costing construction cost, an

estimator need to keep an eye on legislation, to decide which are likely to affect

construction cost and how.

(11) Class of Contractors:

There are various types of contractors in the market. These gives rise to different

classification.

- Small contractors comprises of one man board of directors. They usually carry little

general overhead and keep very few permanent staff

- Medium contractors usually have a board of at least two but not more than five

directors they employ a few more permanent staff, have a reasonable office and

possess some equipment and official cars.

- Large contractors have a lot of times publicly owned with many share holders having

at least six members on their board of directors, fleet of cars and equipments, large

office space and a lot of staffs of various discipline. Generally, the larger the firm, the

higher their cost. Also, the level of profit expected by the share holder of larger firms

is a lot more than that required by the smaller contractors. The rates for the small

contractors therefore tends to be much lower than for large contractors (e.g AG

Ferrero and small firms)

(12) Type of Client:

the type of client or developer can affect the cost of

construction.

Some clients are willing to and are capable of paying more for construction than

others. Also, some clients have methods to be taken into consideration while

estimating construction cost (e.g U.N.T.L will pay on time than N.N.P.C when a

contract is carried out)

(13) Types of Consultants:

31

- Architect: - Some architects are very difficult to work with, their initial designs are

not detailed and they rely a lot on instructions on site. Many variations occur and

delays are frequent. These will add to the cost of construction. The same applies to

Engineers and other designers. Contractors are therefore known to increase their

prices by a certain percentage when it is known that they would be working with

particular consultant.

(14) Types of Tendering:

Open tendering generally brings lower prices than selective tendering, and this in turn

result in lower price than negotiated tendering which brings the highest price of fall.


Use rate analysis to price items in the bill of quantities.

32

WEEK 6: PRICIPLES OF ANALYTICAL ESTIMATING (6.0) 6.1 Elements of a Unit Rate

To analyse something is to break it down into its constituent parts and study each part in

detail. Therefore analytical estimating involves the analysis and costing of construction

resources to produce an estimate.

The production of an estimate normally involves the calculation of unit rates i.e. the cost of

an individual measured item for example a square metre of brickwork, a cubic metre of

concrete or a metre of skirting. As found in a Bill of Quantities.

Analytical estimating is therefore the most accurate form of estimating as each resource and

unit rate is analysed and costed individually. This form of estimating is used for pricing

contracts with bills of quantities, specifications and drawings or where the contractor has

measured and prepared their own quantities of work.


Unit Rates maybe calculated in one of two ways:

Net Rate (Excludes Overheads and Profit) Gross Rate (Includes Overheads and Profit)

Unit Rate

Materials Labour Plant

Overheads Profit

33

In our industry most estimators will calculate costs based on net rates these will then be

enhanced later to include overheads and profit. Gross rates are sometimes referred to as all-

in rates.

The Resources which compromise a unit rate are labour, materials and plant.

In the construction industry labour is often employed in two main ways, these are:

1. Direct

Often referred to as cards in, the employer pays all the costs of employment including for

example national insurance and sick pay amongst others.

2. In-Direct

These workers are self employed or referred to in industry as on the lump these are often

labour only sub-contractors without the normal costs of employment along with the other

legal protections such as redundancy, sick pay and minimum notice periods.

Labour may be paid for on an hourly, daily, weekly or piecework basis. Directly employed

operatives are usually paid in accordance with a working rule agreement which will specify

the rates and allowances to be paid. However, some contractors are trying to move away

from the national wage bargaining and introduce local wage rates. Ultimately the actual rates

paid for labour will depend on market forces.

6.2.1 Materials

Several factors affect the cost contractors pay for materials.

In the box below highlight the factors you think impact on the price a contractor pays.

In the material element of a unit rate, in addition to the actual cost of the material the

estimator must also consider:

Transportation costs Unloading and Stacking costs Materials movement on site Extra Materials to compensate for:

o Wastage o Allowance for materials being measured net in B o Q o Loss in consolidation, shrinkage etc

Note: Where prices of materials are described by suppliers as ex works this means the price

at the factory and delivery costs will have to be added.

6.2.2 Plant

34

Plant may be divided into two main categories, the costs of which can be allocated to

contracts in differing ways.

Non-Mechanical Plant

Basic items of plant including barrows, hosepipes, spades, trestles, scaffolding, small

powered hand tools etc

With the exception of scaffolding and one or two other items it is virtually impossible to

allocate the cost of non-mechanical plant items to a contract, let alone to a specific unit rate

e.g. a wheelbarrow may be used on several contracts in its lifetime.

The cost may be included in overhead charges as a percentage, as a lump sum in the

preliminaries bill or, more accurately, on longer contracts a list of non-mechanical plant items

is prepared, costed and included in the contract sum.

Mechanical Plant

Mechanical plant such as excavators, lorries, dumpers, mixers etc require a more complex

approach. Mechanical plant can be very expensive. Contractors may buy, hire or lease plant.

The purchase of plant must be viewed as an investment on which a return is required. Only

detailed analysis will show whether it is in the contractors interest to buy, hire or lease

mechanical plant.

6.2.3 Overheads

Overheads may be defined as the cost of maintaining (running) the contractors organisation.

There are two types of overheads:

(1) Head Office

Annual cost of staff salaries, expenses, rents, rates, gas, water, electricity, telephones,

office equipment, postage, insurance, maintenance of buildings and equipment etc. The

cost of these items is expressed as a percentage of a companys turnover and included in

the tender.

(2) Project or Site

Project site costs including non productive (manual) site staff, site office costs, storage

facilities and other preliminary / site organisation costs. Items are priced as individual

items and may be fixed or time related costs or a mix of fixed and time related costs. The

costs of these items are included in the tender.

35

6.2.4 Profit

The amount of profit that a contractor can make is determined by a number of factors

largely outside the remit of an estimator. However, in larger companies the senior or

managing estimator may be a member of the management team and in smaller companies

/ firms the estimator may be a director or the managing director. In both cases they may

be party to, or may have to make commercial decisions regarding profit margins.

Factors affecting profit levels are:

Market forces of supply and demand Amount of competition Who the competitor are Size / Value of contract Risk involved in contract Interest rates.

Student Questions

1. Define analytical estimating

2. Explain the difference between net and gross unit rates

3. List the elements of a unit rate

4. Identify the organisations, which produce working rule agreements

5. Define non-productive time and holiday credits.

36

WEEK 7: BUILD-UP HOURLY RATE FOR PLANT & EQUIPMENT (7.0)


The following sections cover the calculation of unit rates. The process of calculating unit

rates could be described as mechanical because you must consider each of the unit rate

elements in turn. Some rates may include all elements, others only one, but you must think

carefully about each element and calculation before commencing.

You may use the Wessex Price Book, or other similar price book, for information on the

output/productivity of labour and plant. Materials and plant prices can be obtained from

builders' merchants and plant hire firms.

In practice estimators must always use productivity outputs analysed from site feedback

and the current cost o f other resourcs.

In the following unit rate calculations the hourly labour rates used are 9.50 for craft

operatives and 7.00 for labour operatives.

7.2 Groundworks

SAQ 2

Explain how the following factors may affect unit rates for groundworks?

Type of excavation e.g. trenches, pits, basements Ground conditions e.g. clay, sand, soil, rock Depth of excavation Ground water Time of year when excavating Mechanical or hand excavation Distance and availability of tips Estimated bulking of materials 7.2.1 Hand Excavation

Excavation work is usually measured in cubic metres (m3)

Typical labour outputs for excavating in firm earth ;

Reduce levels maximum depth 0.25m 3.15 hours/m3

Trenches max. depth 1.00m 3.25 hours/m3

Basements max. depth 2.00m 3.94 hours/m3

37

ADD the following factors for other ground conditions ;

Dry or wet clay 20%

Compact gravel 50%

Rock not requiring a compressor 75%

Running silt or sand 100%

Example

Excavate trench maximum depth 1.00m in firm earth, unit of measurement m3.

Labour;

- p

3.25 hours for a labourer @ 7.00/hour 22 - 75

---------

Net Rate per m3 22 - 75

If you want a Gross Rate add for

overheads and profit, say 10% 2 - 28

----------

Gross Unit Rate per m3 25 - 03

======

TQs 1 - 3

Calculate net unit rates for the following ;

1. Excavate to reduce levels max. depth 0.25m in firm earth,

unit of measure m3

2. Ditto basements max. depth 2.00m in dry clay

unit of measure m3

3. Ditto to reduce levels depth 0.25m in compact gravel

unit of measure m2 (square metres)

7.2.2 Mechanical Excavation

38

Rates for different types of mechanical plant vary enormously between contractors

depending on the method used to calculate the costs.

When calculating all-in hourly rates for mechanical plant the following items should be

considered ;

Capital cost Depreciation Interest on capital Expected life of plant Number of hours worked per annum Maintenance Insurance Road licence Operators wage Fuel Lubricants

Think about how the above factors will affect the hourly cost of mechanical plant.

Example

The following is one method of calculating the all-in hourly cost of a mechanical excavator.

This method is neither the simplest nor most complex method which can be used but it does

produce realistic costs.

Capital cost (purchase price) 37,000

Residual Value (resale/scrap value) 6,000

Interest on capital 6% compound

Expected Life 5 years

Hours worked per annum 1600

Maintenance costs 10% of capital cost per annum

Insurance included in company overheads

Road Licence 200 per annum

Operative's rate 7-50 per hour

39

Fuel 5 litres/ hour @ 40p/litre

Lubricants allow 10% of fuel costs

Standing Charge p

Capital Cost 37,000-00

Less Residual value 6,000-00

-------------

Depreciation 31,000-00

Interest 6% compound on 37,000 over 5 years 12,506-00

Maintenance 10% of capital cost per annum 18,500-00

Road licence 200 per annum for 5 years 1,000-00

-------------

Total for 5 years 63,006-00

-------------

Therefore cost per hour is;

Total cost for 5 years divided by total hours worked in five years

63006 / (1600 hours x 5 years) 7-88

Running Charge

Drivers wages 1856 hours @ 7.50 13,920-00

Fuel 1600 hours x 5 litres/hour x 40p/litre 3,200-00

Lubricants 10% of fuel costs 320-00

-------------

Total for 1600 hours 17,440-00

-------------

Therefore cost per hour is 17440 / 1600hours 10-90

Therefore total cost per hour is:

Standing Charge 7-88

Running Charge 10-90

---------

Total Hourly Cost 18-78

40

======

TQ 4

Using the following information calculate the "all- in" hourly cost for a 16 ton tipper lorry ;

Capital cost 68,000

Residual Value 5,000

Interest on capital 6% compound

Expected Life 10 years

Hours worked per annum 2160

Maintenance costs 10% of capital cost per annum

Insurance 3000 per annum

Road Licence 1,200 per annum

Operatives rate 7-50 per hour

Fuel 10 litres per hour@ 80p/litre

Lubricants allow 10% of fuel costs

7.3 Excavation using Mechanical Plant

Excavate trenches maximum depth 2.00m in clay.

Calculate the net rate per m3 using an excavator with an output of 5m3/hour for excavating

and loading into lorries.

Hourly cost of excavator / output in m3 per hour

18-78 / 5m3 per hour 3 - 76

SAQ 3

The output of the excavator may also be expressed in hours per m3 , what is the output in

hours per m3 ?

Recalculate the rate using your output in hours per m3.

7.4 Banksmen

Banksmen are usually employed to supervise excavator/s. They check the excavation for

obstacles i.e. underground services, make sure the excavator operator is working to the

correct line and level and trim the sides and bottoms of excavations when necessary.

41

TQ 5

Recalculate the last rate and include for one banksman supervising two excavators,

banksmans rate 7.00 per hour.

7.5 Disposal of Excavated Material

SAQ 4

Explain how the following factors may affect the cost of disposing of excavated material

Bulking of material Availability of tips/landfill sites Distance to tip Average speed of lorry Loading time Tipping time Tipping charges/costs Consider alternatives

TQ6

Using the excavator and lorry from the previous example and the following information,

calculate the cost per m3 for disposing of excavated material off site

Note ; The following items are all variables (will vary on every contract) therefore a new

rate must be calculated for each contract

Assume ;

16 ton lorry will carry approx. 6.5m3 of bulked clay

Output of excavator 5m3 per hour

Distance to tip 5 miles round trip

Average speed 20 miles per hour

Tipping time 15 minutes

Tipping charge 20 per load

7.6 Earthwork Support

Defined in the Standard Method of Measurement as ;

Whatever is necessary to support the faces of excavations other than steel sheet piles. It is

measured to the faces of all excavations over 250mm deep.

42

The contractor has to decide what is necessary and cost it accordingly. This is referred to as a

contractors risk item

The following factors affect the cost of earthwork support ;

Ground conditions Depth of excavation Distance between opposing faces of excavation Method of support used

Contractors should also consider alternative methods of construction, which may be less

expensive e.g. over excavate and backfill.

Timber used for earthwork support (EWS) can be re-used up to say 6 times therefore the cost

of providing the timber should be divided by the number of uses to obtain a cost per use.

Operatives fixing EWS are usually paid an additional allowance for skill and responsibility.

Materials

100 x 100 costs 1-92/m

150 x 100 costs 2-88/m

150 x 150 costs 4-32/m

200 x 50 costs 1-92/m

Labour

Fixing EWS in moderately firm earth to faces of excavation up to 2.00m apart and up to

2.00m deep (see sketch) - 0.77 hours per m2

Ditto in loose ground or running sand (as sketch) -

1.65 hours / m2

Hourly rate 7.50 / hour

43

WEEK 8: BUILD-UP UNIT RATE FOR SURFACE EXCAVATION (8.0)

8.1 Surface Excavation

In building up rate for excavation, the following should be considered.

(a) Types of excavation i.e surface or trench excavation

(b) Means of excavation i.e manual or mechanical

(c) Nature of excavation

(d) Volume of excavation (bulking)

(e) Distance of tipping (haulage)

Bulking

Sand 12.5%

Gravel 10%

Clay 133 1/3%

Rock 50%

Multiplier

Medium labour constant multiplier

Sand and gravel 0.75

Natural soil 1.00

Stiff clay 1.50

Soft rock 3.00

Hard rock 8.00

OUTPUT

Excavation 2.5m3 / labour /day

Spreading and leveling 4.5m3 / labour / day

Wheeling / haulage 8.0m3 / labour / day

Placing of concrete 4m3 / labour / day

Task I:

Surface excavation n.e 300mm deep and average 150mm, considered a gang of 12 labour and

the supervisor. Calculate the cost/m3 given that the supervisor is N1500/day and the labourer

N700/day

44

Solution

Labour cost

1 supervisor @ 1500/day N1500

12 labourer @ 700/day N8,400

Add 5% for tools N495

N10,395

Output of gangs / day = 2.5m3 x 12 = 30m3

Labour cost/m3 = 10,395 x 1/30 = 346.50

Add profit and overhead 20% 69.30

Cost/m3 = 415.80

Task II

Cost of spreading and leveling excavated materials n.e 50m from excavation. Consider a

gang of 12 labourers and 1 supervisor

Solution

1 Supervisor @ 1500 = N1500

12 labouers @ 700 = N8,400

5% Tools = 495__

10,395

Output gang / day = 4.5 x 12 = 54m3

Loabour cost / m3 = 10,395/54 = 192.50

Add overhead and profit 20% = 38.50 97.33

8.2 Removal of Excavated Materials

Use wheel barrows when the distinction is less than or equal to 50m .Used lories/tipper.

When the distance is greater than 50m.

Task III

Removal of excavated materials using the same distance of cart away is less than or equal to

50m using the same information used for excavation of surface

Solution

1 Supervisor, 12 labourers and 5% for tools = 10,395

Out out of gang/day 8.0 x 12 = 96m3

Labour cost / m3 = 10,395/96 = 108.28

45

Add 20% profit and overhead = 21.66

225.94

355.88

When lories / tipper are used the following should be considered

(b) Cost of hire or cost of owning

(c) The capacity of the lorry

(d) Total distance to and fro the hill

(e) Speed of lorry

(f) Tipping time

(g) Labour loading the lorry

(h) Bulking of materials

TASK IV

(a) For the cost of hiring plant is 600/hr

(b) Capacity of lorry 6m3

(c) Total distance to and fro is 3km

(d) Speed of lorry 30km/hr

(e) Tipping time 9 minutes

(f) Output of labourer loading the lorry is 2hrs / labour /m3

(g) Bulking of materials 133 %

SOLUTION

Volume of excavated material = 6/133 x 100 = 4.5m3 (assume 4 labour)

loading time = 4.5m3 x 2hrs = 2.25hrs

4

Traveling time = 3km x 60m = 6mins

30km/hr

Total time for loading + traveling + tipping

2.25 + 6m + 9

2.25 = 2.15hr + 6m + 9m

Cost of hiring lorry/hr

= 2.5hrs x N600/hr

= N1500/hr

46

Therefore, cost/m3 = N1500 = 333.33/m3

Labour loading

Cost for 1 labour /m3 = 150/8 x 2.5hr x 4 labour = 187.50

Add 5% for tools = 9.38

196.88

333.33/m3

530.21

Add 20% overhead and profit 106.04

636.25

47

WEEK 9: BUILD-UP UNIT RATE FOR CONCRETE WORK I (9.0)

9.1 Concrete Work

Explain how the following factors may affect unit rates for concrete work ;

Whether ready mixed or site mixed concrete is used Whether concrete is reinforced Surcharges for part loads Location of mixing plant on site Type and size of mixing plant Method of transporting, hoisting, placing and compacting mixed concrete Cost of protecting and curing unset concrete Operatives working with concrete receive additional payments for skill and responsibility.

Items of plant should be priced separately.

Concrete is usually measured in m3

Site Mixed Concrete

TQ 7

Calculate the cost of mixing a m3 of Grade 15 concrete on site using the following

information ;

To produce 1m3 of mixed Grade 15 concrete requires ;

250Kg of cement at 80 per tonne

600Kg of sand at 10 per tonne

1200Kg of aggregate at 9 per tonne

Waste say 5%

Concrete mixer all-in rate 2-50 per hour, output 2m3 per hour

Labour rate 7.20 per hour

Labour out put 0.5m3 per hour

Ready-Mixed Concrete

TQ 8

Calculate the cost per m3 for laying plain concrete 20N/mm2 in foundations over 300mm

thick laid against faces of excavation.

Ready mixed concrete costs 49.00/m3

48

Waste say 5%

Labour output 1.00 hours/m3


SAQ 4

What will happen to the labour output if the concrete is laid in foundations 150mm thick?

Reinforcement is measured separately in bills of quantities. Would you expect the unit rate

for laying reinforced concrete (excluding the cost of reinforcement) to differ from the unit

rate for plain (unreinforced) concrete for similar items of work and if so why?

9.2 Reinforcement

Reinforcement may be bar type or mesh/fabric

Waste

Bars are usually delivered to site already cut and bent, if this is the case then allow 1% for

loss and damage.

If straight bars are to be cut and bent on site allow 5% for waste.

On complex reinforced concrete work steel fixers are usually paid a craft operatives rate.

When laying straight bars or mesh an enhanced labourers rate is usually paid.

Mesh reinforcement is sheet material therefore allowances have to made for general waste

say 2.5% plus an additional allowance for laps. The percentage to allow for laps will depend

on the lap specified e.g. 150mm side and end laps.

TQs 9-10

Sheets of mesh are approximately 4.80m x 2.40m if they are to be laid with 150mm side and

end laps what % must be allowed for loss in cover due to the laps ?

Mesh reinforcement Ref. A193 in beds laid with 200mm side and end laps.

Calculate the rate per m2.

Mesh costs 14-00 per sheet

Labour 0.05 hours / m2 at 7.20 / hour

Allow say 20p / m2 for spacers and tying wire


Throughout this and the series of learning packs you will find, extensive notes on the various

aspects of work you will be measuring followed by a series of three tasks, These tasks are

49

designed to increasingly develop your skills in the aspect of measurement covered by the

learning pack, and will include, one basic task, which requires you to copy down a worked

example, using the correct measurement layouts. The second task and third tasks form the

second section of the class, where the class develops into a tutorial based

9.4 Concrete Works

As with groundwork, before looking at the calculation of unit rates we must understand that

our final unit rate will be influenced by several variables.

Task One

In the box below, describe how you think the following factors would impact on cost.

When considering concrete there are two main methods of producing concrete:

1. Site mixed concrete

2. Ready mixed concrete

In addition to the method of concrete production when costing concrete work we must also

consider concrete accessories including:

1. Formwork

2. Reinforcement

3. Operatives working with concrete usually receive additional payments for skill and

responsibility

4. Items of plant concerned with concrete mixing and placing are usually measured

separately.


1. Ready mixed or site mixed concrete

2. Whether the concrete is reinforced or un-reinforced

3. Surcharges for part-loads

4. Location of site in reference to mixing plant

5. Type and size of mixing plant

6. Method of transportation, hoisting, placing and compacting mixed

concrete

7. Protection of un-set and curing concrete

50

Calculate the cost of mixing one m3 of grade 15 concrete on site using the following

information:

The production of 1m3 of grade 15 concrete requires:

250kg of cement at 92.70 / tonne 600Kg of sand at 17.25 / tonne 1200kg of aggregate at 18.02 / Tonne Waste allowance say 7.5% In addition allow for:

concrete mixer @ all in rate of 3.00 / hr Labour rate @ 8.68 / hr

9.4.2 Ready Mixed Concrete


thick laid on or against earth or unbinded hardcore.

Ready mixed concrete say 80.59 / m3 Waste say 5% Labour output = 1.00hrs / m3 Labour rate 8.68 / hr Questions:

1. How would the labour output be affected if the concrete is laid in foundations 150mm

thick?

2. What would be the financial impact? (If any)

9.5 Concrete Reinforcement

Reinforcement is measured separately in bill of quantities. Would you expect the unit rate for

laying reinforced concrete (excluding the cost of reinforcement) to differ from the unit rate

for plain (unreinforced) concrete for similar items of work, if so why

Reinforcement maybe either bar reinforcement or mesh / fabric reinforcement.

Waste


loss and damage.

If straight bars are to be cut and bent on site allow 5% waste


When laying straight bars or mesh an enhanced rate is usually paid.

51

Mesh reinforcement is sheet material therefore allowances have to be made for general waste,



Qu 1.


end laps what percentage must be allowed for loss in cover due to the laps?

Qu 2

Calculate the rate per m2 for laying mesh reinforcement Ref A193 in beds, laid with 200mm

side and end laps.

Additional information

Mesh costs 15.08 per sheet Labour 0.05hrs / m2 @ 8.68 / hour Allow say 20p / m2 for spacers and tying wire Waste on mesh 5%

52

WEEK 10: BUILD-UP UNIT RATE FOR CONCRETE WORK II

9.6 Concrete Work

Explain how the following factors may affect unit rates for concrete work;

Whether ready mixed or site mixed concrete is used Whether concrete is reinforced Surcharges for part loads Location of mixing plant on site Type and size of mixing plant Method of transporting, hoisting, placing and compacting mixed concrete Cost of protecting and curing unset concrete Operatives working with concrete receive additional payments for skill and responsibility.

Items of plant should be priced separately.

Concrete is usually measured in m3


TQ 7

Calculate the cost of mixing a m3 of Grade 15 concrete on site using the following

information ;

To produce 1m3 of mixed Grade 15 concrete requires ;

250Kg of cement at 80 per tonne

600Kg of sand at 10 per tonne

1200Kg of aggregate at 9 per tonne

Waste say 5%

Concrete mixer all-in rate 2-50 per hour, output 2m3 per hour


9.6.2 Ready-Mixed Concrete

TQ 8


thick laid against faces of excavation.

53

Ready mixed concrete costs 49.00/m3

Waste say 5%

Labour output 1.00 hours/m3


SAQ 4

What will happen to the labour output if the concrete is laid in foundations 150mm thick?

Reinforcement is measured separately in bills of quantities. Would you expect the unit rate

for laying reinforced concrete (excluding the cost of reinforcement) to differ from the unit

rate for plain (unreinforced) concrete for similar items of work and if so why?

9.7 Reinforcement

Reinforcement may be bar type or mesh/fabric

Waste


loss and damage.

If straight bars are to be cut and bent on site allow 5% for waste.


When laying straight bars or mesh an enhanced labourers rate is usually paid.

Mesh reinforcement is sheet material therefore allowances have to made for general waste



TQs 9-10


end laps what % must be allowed for loss in cover due to the laps ?

Mesh reinforcement Ref. A193 in beds laid with 200mm side and end laps.

Calculate the rate per m2.

Mesh costs 14-00 per sheet

Labour 0.05 hours / m2 at 7.20 / hour

Allow say 20p / m2 for spacers and tying wire

9.8 Concrete Work

Concrete

Material

- cement

54

- sand

- aggregate

plant concrete mixer, poker, vibrator

1m3 of .. weight 1440

TASK

Example a tonne of cement cost N14,000, sand cost 560/m3, coarse aggregate cost 900/m3 for

a mix of 1:2:4. Calculate the cost/m3

Solution

1m3 cet will cost 1.44 @ 14,000 = 20,160

2m3 of sand will cost 2 x 560/m3 = 11,120

4m3 of aggregate will cost 4 x 900/m3 = 3,600

24,880

7m3 = 24,880

1m3 will cost 24,880 = N3,554.29

7

Add 50% of void and compaction 1,777.14

5,331.44

Add 20% overhead and profit 1066.29

6,397.73

Mix shrinkage broken stone

cement sand agg cement sand agg

tonnes m3 m3 tonnes m3 m3

1:1:2 0.524 0.36 0.72 0.552 0.38 0.76

1:2:4 0.304 0.42 0.84 0.32 0.44 0.88

1:3:6 0.440 0.44 0.88 0.23 0.46 0.92

(void and compaction here have been taken care of)

Plant

Cost of mixer/hr

The cost of owning and operating a 10/7 concrete mixer. Assume initial cost of N150,000, a

scrap value of N10,000

Life span of 6yrs @ 2000 hrs/year

Compute the cost/hr

55

Capital cost/hr = initial cost scrap value

Life span (hr)

Therefore, Capital cost/hr = 150,000 10,000 = N11.66/hr

6 x 2000

Running cost

Repairs and maintenance 10% of capital cost

= N1.17/hr

Fueling 1.8 liters @ N22 = 39.60/hr

Oil and grease 20% of capital cost = 2.34__

43.71/hr

Cost of concrete mixer

Cost of mixer / day = 54.77/hr x 8hrs = 438.16

Cost of labourer / day 8 labour @ N400 = 3,200

Add 5% for tools = 160_____

Cost of labour and mixer 3,798.16

Assume output of mixer / day = 20m3

Therefore, cost /m3 = 3,798.16 = N189.91

20m3

Cost of placing concrete in foundation

6 labourers need @ an output of 4m3/day

Cost of 6 labourers = 6 x 400 = 2,400

Add 5% for tools 120

Cost/m3 = 2,520 = 630 4

Cost of concrete in foundation

Cost of conc /m3 = N6,397.73

Add 5% of waste 319.88

Cost of mixing / m3 189.91

Cost of placing 630

Add 20% for overhead and profit 7,537.52

1,507.51

N9,045.04

56

WEEK 11: BUILD UP UNIT RATES FOR REINFORCEMENT (11.0) 11.1 Bar Reinforcement Most bar reinforcement is bought in straight length of about 16ft. It is usually

priced in tonne (1000kg) reinforcement supplied to site in which cost of

transportation is not included in the calculation for unit rate, labour cost for

unloading and stacking, cutting, bending and fixing are calculated. Some times

bar reinforcement can be purchased already and bend to shape e.g links and

stirrups and labour cost calculated will then only include the cost of fixing on site.

Allowance for bending wire at intersections has to be made. The labour output

should be taken as follows

Cutting and bending

Diameter 6 8 10 12 16 20 25 32 40 50

Hours 63 45 35 27.2 22.5 15 12.5 10 8 6

Fixing/tonne

Diameter 6 8 10 12 16 20 25 32 40 50

Hours 63 45 35 27.2 22.5 15 12.5 10 8 6

NOTE:

1. Assume 3hrs for unloading 1 tonne of reinforcement

2. Allow 5% waste for cutting form straight length

3. Allow 1% waste reinforcement already cut to shape

4. for bars in short length e.g links and stirrups, allow 33% for extra labour

Tying wire/tonne

Diameter 6 8 10 12 16 20 25 32 50

Hours 15 15 12 10 8 8 6 5 4

Allow say N1000/tonne for spacers (biscuit)

TASK I

16mm mild steel bars reinforcement in straight and bent bars in suspended slab

kg

Solution

57

A Material Labour

A1 16mm

A2 Tying wire B1 Cutting and bending

A3 Spacers B2 Fixing

A1 Materials/tonne (1000kg)

Assume cost of 16mm @ 34,000/tonne = 34,000

Unloading and stacking 3hrs@400 = 1,200_

35,200

Allow 5% for waste 1760_

36,960

A2 Tying wire

Assume 8kg @ 60/kg = 480

Allow 5% for waste 24__

504_

A3 Spacers = N1000

Allow 3% waste 30

1030

Material collection

A1 36,960/tonne

A2 504/tonne

A3 1030/tonne)_

38494/tonne

Labour

B1 Cutting and bending

22.5hrs @ 50/hr = 1,125

B2 fixing: 22.5hrs @50/hr = 1,125

Labour collection

B1 = 1,125

B2 = 1,125

2,250

Summary

Material = 38,494

Labour = 2,250_

40,744

58

Add 25% O/P = 10,186_

50,930/tonne

Cost/kg = 50,930 = 50.93

= N51/kg

59

WEEK 12: BUILD-UP UNIT RATE FOR FORMWORK (12.0)

12.1 Formwork

Formwork measures the actual faces of work covered or to be supplied. The

following must be taken into consideration in determining the size of the formwork

1. The amount of material required

2. The kind of finishes required i.e sawn faced or smooth finish, ground finish,

biscuit etc. This determine the types of materials to be used as formwork and the

surface from finish required is removed.

3. the height to be supported. This determine the height of props and types of

props.

4. Normal labour for fabricating, erecting and striking of formwork.

5. the number of uses required of the formwork this is usually a matter of

experience.

In small contract it may be possible to reuse the same formwork twice depending on

the repetitive nature of the work.

Materials

Materials Unit Rate

1 x 12 x 12 sawn Length 130

1 x 12 x 12 wrought Length 230

2 x 4 x 12 Length 120

4 x 4 x 12 Length 180

5 nails Kg 135

4 nails Kg 135

3 nails Kg 135

60

2 nails Kg 150

Labour output are mostly conveniently calculated/m3 of timber

Labour output for suspended slab

Description Output

Unloading and stacking 2.5m3/lbour/day = 250

Cutting, fabricating and erecting 0.80m3/gang/day (2carpenters + labour

Striking 12m2/gang/day

Allowance for waste

Cutting and fixing of timber 10%

Nails 20%

TASK I

Sawn formwork to horizontal soffit of suspended slab m2

Assume 3m height above floot level

Solution

Materials

A1 1 x 12 x 12 softwoods planks

A2 2 x 4 hardwood battens

A3 4 x 4 hardwood props

A4 4 nails

Labour

61

B1 Unloading and stacking

B2 Cutting, fabricating and erecting

B3 Striking

NOTE:

3.6 x 1.2 for the calculation and divide by 4.32m2 after all to arrive at cost/m2. This

convenient size allow for more length of timber piece to be used and there by

simplifies the calculation

A1 4nr sawn softwood planks @ 180 720.00

Add 10% waste 72.00 792.00

A2 2 x 4 x 12 battens 2 x 3.6 = 7.2

4 x 12 = 4.8

12.00

12.00m = 3 length or 3.33 + 1 = 4 x 480.00 3.6m

Allow 10% waste 48.00_ 528.00

A3 props @ 1.00m c/c

4 x 4 x 12 props 8nr x 3 = 24m

24 7 lengths @ 180 1,260

36 add 10% for waste 126_ 1,386

A4 1kg of nail 4 @ 135 135.00

Allow 20% waste 27.00 162.00

62

Material for collection

A1 792.00

A2 582.00

A3 1,386.00

A4 162.00

N2,868.00

Assume 3 uses

Cost/use = 2,868 = 956 3

Cost/m2 = 956 = 239 4.32

Labour

Volume of timber

25 x 300 x 3600 x 4nr = 0.108

50 x 100 x 3600 x 2nr = 0.0136

50 x 100 x 1200 x 4nr = 0.24__ 0.408

Allow 10% for waste 0.041___ 0.449m3

Unloading and stacking

2.50m3 = 1 labour / day = N250.00

Therefore, 0.45m3 = 700 x 0.45 = N126 = 126 2.5

Cutting, fixing and erecting (gang)

2 carpenters @ 1500 = 3000

1 labour @ 700 = 700_ 3,700 0.8m3 = 1 gang/day = N3,700

63

0.45m3 = 3,700 x 0.45 = 2,081.25 = 2,081.25 0.8 Striking

12m2 = 1 gang/day = 3,700

4.32m2 = 3,700 x 4.32 = 1,332 = 1,332__ 12m 3,539.25

Labour cost collection

Cost of labour = 3,539.25 = N819.27 4.32

64

Summary

Materials = 221.30

Labour = 819.27 1,040.57

Add 25% P/O 260.14_ N1,300.71

65

WEEK 13: BUILD-UP UNIT RATE FOR ROOFING (13.0)

13.1 Roofing

Corrugated roofing sheet, operation output /gang / day

Aluminium of galvanized iron unloading + fixing 40m2

Fixing ridge cap 35m

Raking and cutting 30m

Straight cutting 30m

Asbestors unloading + fixing 30m2

Fixing ridge cap 20m

Raking + cutting 25m

Straight + cutting 25m

Felt roofing unloading + laying of layer 120m2

Spreading bitumen primer 80m2

Spreading bitumen 80m2

Spreading chips 100m2

Laying gutters < 1m girth 20m

Raking cutting 90m

TASK I

0.7mmm thick corrugated aluminium long span roof covering fixed to timber purlins (m.s)

@900mm c/c with 50mm galvanized drive screw with felt and metal washer including

100mm side laps (measured net) in m-square i.e (100mm2)

(A) Materials

A1 0.7m long span Aluminium sheet

A2 Galvanized drive screw + washers

66

(B) Labour

B1 Unloading and fixing

Laps = (0.75 0.10) x 1m

= 0.65m2

A1 roofing sheet required = 100m2

0.65m2

= 153.85

Add 5% for waste 7.70

161.55m2

Cost/m2 = N1200

161.55@1200 = N193,860

A2 Galvanized drive screw

Number required = 4no/m2 x 100m2 = 400nr

Allow 10% for waste 40______

440 pieces

N6/screw

Cost 440 pieces @ N6 = N2640

Material collection

Corrugated roofing sheet N193.860

Screw + washer 2,640__

196.500

Labour

A gang / day

2 carpenters (roofers) @1500/day = N3000

1 labourer @700/day = 700

=N3700

Add 5% for tools =_185_________

3885/gang/day

Unloading and fixing 1 gang /day output = 40m2

67

40m2 = 1 gang / day = N3885

100m2 = 3885 x 100m2 = 9,712.50

40m2

Summary

Materials N196,500.00

Labour 9,712.50__

206,212.50

Allow 25% for profit and over head 51,553.13__

257,765.63

Therefore, cost/m2 = 257,765.63 = N2577.66

100m2

TASK II

2 layers of bituminous felt roof covering laid on flat weighing 25kg/roll of 20m2 with 100 and

150mm end and side laps respectively and finished with 6mm chipping. Assume 100m2

covering.

MATERIAL LABOUR

(1) Felt (2 layers ) unloading + fixing of felt

(2) Bitumen primer spreading bitumen primer

(3) Bitumen (3 layers) spread bitumen

(4) chipings spreading chippings

Plant

Boiler

A1 laps

(20m x 0.15m) + (0.085 x 0.10m) = 3.085m2 = 3.09m2

Covering capacity / roll = 20.00m2

Less laps 3.09____

16.91m2

Nr of rolls required = 100m2 = 5.91 roll

Allow 3% for waste = 0.18

6.09 roll/layer

Therefore, 2 layers will be required = 6.09 x 2 = 12.18 rolls

68

12.18 rolls@2500 = N30,450

Bitumen primer

A2 Assume a covering capacity of 7m2/liters

Therefore, bitumen required 100m2 = 14.29 liters

7 liters

Allow 5% waste 0.71_____

15.00 liters

20 liters / drum = 1600

Therefore, 15 liters will cost 1600 x 15 = N1,200

20

A3 Bitumen (3 layers)

Assume a covering capacity of 2kg

(m2 bitumen required / layer = 2 x 100m2 = 200kg

Allow 10% for waste 20

220

For 3 layers x 3

660kg

480kg / drum of R115 / 15 (type) cost N20,000

Therefore 660kg will cost 20,000 x 660 = N27,500

480

A4 Assume a covering capacity of 60m2 / tonne

Chippings of tonne required = 1/60 x 100m2 = 1.67 tonne

Or 100m2 / 60m2 1.67 tonnes

If 1 tonne of chippings cost N7,000

Therefore 1.75 tonnes will cost 1.75 x 7000 = N12,250

69

Material cost collection

A1 felt = 30,450

A2 primer = 1200

A3 bitumen = 27,500

A4 chippings = 12,250

N71,400

B1 unloading and fixing

Output = 120m2/gang/day (felt)

100m2 = 1/120 x 100 = 0.83 (a layer)

2 layers = 2 x 0.83 = 1.66

B2 Output = 80m2 / gang / day (primer)

= 100m2 = 1/80 x 100 = 1.25

B3 Output = 80m2 / gang / day (bitumen)

3 layers = 3 x 1.25 = 3.75

Chippings 1.00

7.66

B4 Output = 100m2 / 100m (chippings) = 1.00

7.66 gang @ N1,575 = N12,064.50

(d) PLANT: cost of plant/hr N150

Cost of plant/day N150 x 8hrs = N1200

Summary

A. Material = 71,400.00

Labour = 12,064.50

Plant = 1,200.00

84,664.50

Add 25% profit and overhead 21,166.50

105,830.03

Cost/m2 = N105,830.63 = 1,058.31

100m2

70

NOTE:

Allowance has to be made for the following

- Irregularity of surfaces

- Compression of toweling 80%

- General waste (residue + application)

TASK I

12.5mm thick c/s (1:4) rendering trowel smooth

(a) Wall

(b) Concrete soffit (100m2)

Material labour

Cement 1m3 mixing

Sand 4m3 rendering

5m3

1m3 cement 28 bags @ 700 = N19,000.00

Transport, loading and unloading 28 bags @ 10 bags = 280___

19,880

Allow 2% waste 397.00

20,277.60

4m3 of sand

4m3 of sand @ N600/m3 = 2,400

Allow 5% for waste = 2,520

Cement = 20,277.60

22,797.00

Allow 25% for shrinkage 5,699.40

28,497.00

Cost/m2 = 28,499

5m3

= N5,699.40

Volume of mortar required 100m2 x 0.0125m3

1.25m3

Allow 80% 1.00___

71

2.25m3

Therefore, 2.25m3 of mortar @ 5,699.40 = 12,823.65

Labour

1. Mixing = 1m3 = 1 labour day@ N700/day

2.25m3 = N700 x 2.25m3 = N1575

2. Rendering = 30m2 = 1 gang/ day = N3885 (reference to roof)

100m2 = N3885 x 100m2 = N12,950

30m2

Labour

1. Mixing 675

2. Rendering 12,950_

13,625.00

Add 5% for tools 681.25__

14,306.25

Summary

Material = 12,823.65

Labour = 14,306.25

27,129.9

Add 25% P/OH 6,782.48_

33,912.38

Cost/m2 = 33,912.38 = N339.12

100

72

WEEK 14: BUILD UP UNIT RATE FOR MASONRY (14.0)


Throughout this and the series of learning packs you will find, extensive notes on the various

aspects

Documents

Quantity Surveying Book