CONSTRUCTION COST ESTIMATE AND

ANALYSIS 1

ECE 4106

B. Tech - Civil Engineering

Year 4.1
 Course Outline:
• Introduction to quantities: Form, order, procedure in specification writing.
• Cost Estimates - Squaring, subtraction, billing, preliminary, preamble clauses, bills
of quantities, approximate quantities, cost planning and analysis.
• Data communication in construction industry and its application in tendering and
construction processes.
• Contracts, unit rates, estimating costing, prime cost, provisional sums, day work,
interim certificates, general economy factors, defects liability, fluctuations, antiques,
arbitration.
• Computer production of bills.
 Expected Learning Outcomes:
At the end of this course the student should be able to:
1. Describe the process of project cost estimating.
2. Analyze and calculate cost estimates of a project as per the bill of
quantities.
3. Outline various methods of data communication in construction
industry and its application in tendering and construction purposes.
4. Enumerate and explain various types of contracts.
5. Use computer techniques in production of bills.
 Course Assessment:
• Continuous Assessment Tests (CATs) - 15%
• Regular assignments - 15%
• Final Examination - 70%
• Class Attendance - Very important
 Course References:
Course Textbook
1. Allan. A . & Srinath P. (2015). Cost Studies of Buildings. 6th Ed.
Reference
1. Keith P & Ankrah N. (2014). Construction Cost Management.
Rutledge. .
 Specification
• Specification - is a statement of particular instructions of how
to execute some task.
• It is a formal contractual document used during the tendering
stage of a project and for reference/guidance during the
implementation stage of a project.
• It contains detailed descriptions of the quality of materials,
equipment and workmanship required to successfully complete
the work.
• It is usually accompanied by drawings that are image illustration
 Items in a Specification
• Type and quality of materials, equipment, labor or
workmanship.
• Methods of fabrication, installation and erection
• Standards and codes to be used
• Allowance submittals and substitutions
• Cost included, insurance and bonds
• Project record
• Site facility
 Items in a drawing
The drawing that accompany specifications have the following
items:-
• Dimensions, extents, size, shape, and location of component
parts.
• Location of materials, machineries and fixtures.
• Interaction of furniture, equipment and space.
• Schedules of finishes, windows and doors.
 Aspects of a Specification
Specifications are written based on:-
• Project design, trends of workmanship, Quality expected, Equipment
required and Materials to be used.
Specifications should clearly specify:-
• Project design, working drawing details, materials to be used, labor to
be employment, construction method to be used, standards and codes to
be used and equipment to be used.
Specifications should be:-
• Clear, concise, and brief describing of what is required to execute the
works.
 Example of a specification

Share an actual specification from a project.

 Purpose of a Specification

What are the purpose of Specification?

 Purpose of Specifications
• Contract document - describes the obligations of each party bound by
the contract.
• Tendering – Guide the bidders to arrive at reasonable costs by outlining
what the client expects.
• Enable proper quality control – The supervising team is able to refer
to the specification when work is done for quality control
• Mitigates contractual disputes – All parties in a contract should
ensure that work is done according to the specification to reduce disputes
 Purpose of Specifications
• Provide guidance of project expectations
• Guides contractor for the purchase of materials – quality and quantity
• Serve as fabrication and installation guide for temporary and permanent
works.
• Guide the contractor for purchase and/or hiring of equipment.
• Guide the manufacturers of construction materials, equipment, tools
• Guides in expected methods of testing and acceptance of final products.
• Guide parameters for rejection of non-conforming works.
 Classification of Specifications
Specifications are classified based on two major aspects
• Specifications based on purpose
• Specification based on area of work
 Specifications based on purpose
1. Manufacturer’s specification – Prepared by product manufactures for
guidance of their users, which may include product description and
installation guide lines.
2. Guide specification - Prepared by an individual or organization based on
manufacturer’s specifications. Provide guidelines based on established trends
of workmanship, service and laboratory tests, research findings to be used for
preparation of contract specification.
3. Standard specification - prepared and standardized by recognized
authorities. E.g. British Standards used for civil engineering works.
4. Contract (Project) Specification: The specification prepared for a particular
project to accompany the drawings and other contract documents.
 Contract (Project) Specification
Contract specification can be prepared in two formats:
• General Specification – A formal document containing written
instructions applicable to similar types works. E.g.
Specification for public road construction works.
• Specific specification - A formal document containing written
instructions applicable to specific type of work – E.g.
Specification for a private access road to a residential area.
Note: General specifications are mostly accompanied by special
specifications for works that are unique to that specific project.
 Contract (Project) Specification
Items in the general specification include:
• Project description
• Site facilities.
• Administrative and procedural requirements
• Project scope
• Reference organizations and standard codes
• Submittals and quality assurance
• Delivery, storage and handling of materials/equipment
• Project records, insurances and other general requirements
 Specifications based on area of work
They include:-
• Material Specification
• Workmanship Specifications
• Performance Specifications
 Material Specification
• Specify the acceptable material quality and quantity.
• This will describe the material type, composition and
performance properties
• Their description include:-
• Physical properties; color, texture, pattern and finishes
• Mechanical properties; strength, durability, hardness etc.
• Chemical composition
• Electrical and thermal properties
 Workmanship Specification
Specify the construction methods to be employed.
The description include:-
• Specify the desired results in terms of quality of workmanship
• State any detailed construction methods or procedures necessary for the
accomplishment of particular work.
• Stipulate any desired limitations or restrictions to be placed on the
contractor's methods in the interest of coordination of the work.
• Give any precautions necessary for the protection of the work or adjacent
property.
• Specify the methods of inspection and tests to which the work is to be
assessed with
 Performance Specifications
Specify performance requirement for machinery and plant operating
equipment. They include:-
• Proprietary specification – Defines performance of products based on
brands
• Performance specification – Defines products based desired results
• Reference specification – Define products based on required quality.
• Descriptive specifications – Defines product based on all components of
assembly. The specifier is liable for the function and performance of the
product.
• Cash Allowance specification – Items are defined based on the amount of
money to be used for the works.
 Specification Writing
• Specifications are prepared based on existing standards, codes,
guidelines, and laws.
• Factors to consider when planning to write a specifications:
• An overall analysis of the work to be done.
• The requirements necessary to achieve the required level of quality.
• Conditions under which it must be done.
• Materials required.
• Details of the construction
 Guidelines in Specification Writing
Some of the guidelines that one needs to follow when preparing a
specification include:-
➢Be specific, use correct grammar
➢Be brief and clear, avoid unnecessary words or phrases
➢Give all the necessary facts
➢Avoid repetition
➢Specify in the positive form only the items intended to be executed
➢Be fair and do not attempt to throw all the risks to one party
➢Direct rather than suggest
➢Use short rather than long sentences
 Requirements for Specification Writing
Specification writing requires:
1. Visualization, research, clear thinking and organization (order).
2. Professional ability to understand and interpret drawings.
3. Wide knowledge of the construction practice; materials,
workmanship, equipment, contractual terms and documents
4. Knowledge of all items affecting the cost of the work.
 References for Specification Writing
Some of the references used in specification writing include:-
a) Codes and ordinances of governments, cities, or municipalities. E.g.
EBCS
b) Standards prepared by distinct societies and government agents.
E.g. ACI standards, ASTM standards, BS, ES.
c) Standards or model specifications prepared by manufacturers,
professional societies, and government bodies.
d) Master Specification and previous specifications.
e) Information and/or experience acquired by personal observation
and contract with trained or experienced people in the construction
industry.
 Bill of Quantities (BoQ)
To Discuss:
• Definitions and purpose
• Preparation of BoQ
• Taking off
• Squaring
• Abstracting
• Billing
• Example of a BoQ
 BILL OF QUANTITIES
Bill of Quantities is a list of brief description of works and
estimated quantities for civil engineering projects.

Purpose:
• Assist bidders during tendering process
• Assist in contract administration
• Defines the expectation of quantities and costs during work
implementation.
 PREPARATION OF BILL OF QUANTITIES
There are four steps in preparation of Bill of Quantities
• Taking off - The process of measuring and recording dimensions from
drawings
• Squaring - The process of multiplying, adding, subtracting or dividing the
recorded dimensions for the purpose of obtaining quantities.
• The quantities are in form of linear measurements, areas, volumes, etc.
• Abstracting – Transfer and cumulation of squared quantities/dimensions of
similar category to an abstract sheet to obtain the total quantity of an item.
• Writing of final Bill of Quantities – It is the transfer of all the measured
quantities/dimensions from the abstract sheets to the BoQ and multiplying
them with the unit rates to get the cost estimates of the work.
 TAKING OFF – Cont’d
• The dimensions recorded are used to determine the volume of work.
• Quantities are recorded and calculated in an organized format called the
“Take off sheets” or “Dimension paper”.

A Take off sheet is composed of four columns:

a. Column 1 – Timesing Column
b. Column 2 – Dimensioning Column
c. Column 3 – Squaring Column
d. Column 4 – Description Column
 Take off sheet Columns
1. Timesing Column – indicates the number of times an item occurs.
2. Dimensioning Column – records the dimensions of items of work.
Order of recording is Length, Width then Height or thickness.
3. Squaring Column – Multiplies the stated dimensions in column 2
to obtain the volume of works.
4. Description Column - Briefly describes the work measured

N/B: Reinforcement quantities are prepared on a sperate sheet called

the bar schedule
 Example of a Take off sheet
a) Blank Take off sheet: b) Filled Take off Sheet
Example of a Bar Schedule
Example of a blank Bill of Quantities worksheet
Example of a filled Bill of Quantities worksheet
 Developing of Bill of Quantities - Example
The figure below shows a plan and cross section of a building foundation. Determine the
volume of the excavated and backfilling material, then prepare a bill of quantities on the
same. Take a general excavation and backfilling cost of Ksh.880 and Ksh.525 per cubic meter,
respectively.
 Developing of Bill of Quantities - Example
Solution
1. Excavation: Take off excavation measurements
The length of excavation
Length = 5.4 × 2 + (4.4 – 2) × 2 = 15.6 m
Depth of excavation
Depth = 1.8 m
Width of excavation = width of plain concrete footing
Width = 1.0 m
Excavation Volume = 15.6 × 1.8 × 1.0 =28.08 m3
 Developing of Bill of Quantities - Example
2. Backfilling – Take-off backfilling measurement from the
diagram
Volume of backfilling = excavation – concrete – brick
Volume of concrete
= 15.6 × 1 × 0.4 = 6.24 m3
Volume of brick
= 15.6 × 0.4 × 1.4 = 8.736 m3
Volume of backfilling
= 20.08 – (6.24 + 8.736) = 13.104 m3
 Developing of Bill of Quantities - Example
Item Description Unit Quantity Unit price Total price
(Ksh) (Ksh)
 Developing of Bill of Quantities - Example
Item Description Unit Quantity Unit price Total price
number (Ksh) (Ksh)
1.0 Excavation for m3 28.08 880 24710.4
building of
foundation
1.1 m3 13.104 525 6879.6
Soil backfilling after
foundation
construction
TOTAL 31590