COST ESTIMATION
Dr. Ali A. Shash
الدكتور علي علي شاش
Detailed Estimating Method
Contractor’s Method
Importance of accuracy of Cost Estimate
Cost Estimator Characteristics
Accuracy of Cost Estimate
Why Estimate should be accurate?
Accuracy of the Estimate is necessary for the following
reasons:
Quality of the project design
Ability to start a construction
Project success for the owner
Financial success for the constractor
Financial commitment
Owner
Contractor
A/E
Estimating Methods
Two Methods for Pricing a Project
Method 1: Unit Cost Estimate Approach
Work Cost = (SR/quantity) x Proposed Quantity of
Work
Inthis method productivity is considered indirectly by
means of correction factors. However, this method
Payslittle respect to method of work
Type of project and size
Weather, worker morale and mgt. & supervision
Estimating Methods
Two Methods for Pricing a Project (Continued)
Method 2: Resource Approach
Relies on productivity data
Labor Cost = wage rate (SR/hr) X time needed (hrs)
Time needed = Quantity of Work (output Unit)/labor
Productivity (output unit per hr)
= hrs
Labor Cost = (Quantity/productivity) X Wage rate +
Miscellaneous
Detailed Cost Estimate
The preparation of an accurate construction estimate
requires
1. Quantity of work to be performed
2. Productivity of resources to be used for the work
3. The cost of materials to be fabricated
4. The cost of resource to used
Number From
1 Drawing & Specs
2, 4 Usually from the Contractor’s records
3 Suppliers
Detailed Cost Estimate
Successful Preparation of Construction Estimate
Determination of the work to be performed
Determination of the Productivity of the resources used
for the work
Determination of the cost of resources
Detailed Cost Estimate
Project Document
Understand the Scope of the project
Agreement
Drawings
Specs
Conditions of the Contract
Addenda
Detailed Cost Estimate
Work Breakdown Structure
Villa Example
Concrete Work
Villa
Foundation Structure W&D Electrical Mechanical Walls
Excavation Formwork Rebar Concrete
#10 #12 #9
Detailed Cost Estimate
The soundness of an estimate depends on the
following two factors
The accuracy of the quantity take-off
The selection of the unit costs and production rates to
be used
Quantity Take-Off
Quantity Take-Off is the calculation of work quantities
to be performed as set out on the two dimensional
project drawings
Estimator is to define a work package (work item). Each
work item should be defined in away that an estimator
can take off quantities from drawings and contractor
can collect historical data for pricing work
Whenever one or more different resources are required
to perform work, then each resource required is
identified as separate work item (WBS)
Quantity Take-Off
What is the unit of measure?
# of Units, weight, length, area, volume, ----
What is the dimension of the unit of measure?
Area:Square Centimeter, Square meter,
Volume: Cubic Centimeter, Cubic meter
How to select?
Select the measure of work that reflect the costing of
work
Example: Concrete: Cubic Meter, Materials : SR/unit,
Quantity Take-Off
The working drawings:
Building Drawings (General Condition Drawings)
Specialized Drawings
Detailed and Section Views
Building Drawings:
Plot plan
Foundation plans
Floor plans
Elevation drawings
Windows and Doors schedule
Interior Finish drawings
Quantity Take-Off
Specialize Drawings (Very Technical)
Electrical
Plumbing
Heating and air conditioning work
Mechanical
Detailed and section views
Detailed: enlarge a section of the drawing in order to
better illustrate the type of construction work
Section: represents a cut through a wall, floor, ceiling section
of the building
Display reinforcement in a wall, floor, or ceiling
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
For each defined item obtained from the WBS:
Determine the Order of Quantity Take-Off bottom up
Begintake off in the same place for each drawing and
proceed in a pre determined fashion (i.e. clockwise)
Check off each item as they are completed
Details
Section
Items on specs
Other items on collection sheets
Orby using a checklist to reduce or eliminate unintentional
omissions of quantity take-off items
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
List items in a set order (Length, Width, Height)
Use standardized forms for taking off
The use of standardized form serves two purposes:
Repeated process will insure efficiency and accuracy
Ease communication between the contractor’s estimators
and non estimators personnel.
Estimating forms could be obtained from two sources:
Contractor self designed forms
Standardized Estimating Forms
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
Forms should be in set of 3 sheets:
The Quantity Sheets:
Used for taking off and determining of work quantities
The form consists of all the element that are necessary for
taking off
Description
Dimensions (set order Length, Width, Height)
Quantity
Necessary when a significant amount of sub-calculations
are required
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
General Estimate Sheet
Contains all information that is in the quantity sheet. In
addition, it has unit resource cost that are functions of
the quantity.
The Estimate Summary Sheet
Serves to sum the cost of doing the individual work
items that are determined in the General Estimate
Sheet. In addition, it serves as a worksheet for
summarizing various miscellaneous project costs
including Job OH
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
Use mathematical Procedure that enhance the
efficiency of preparing an estimate while
maintaining or improving accuracy
Utilizethe result of a certain calculation several times to
determine the quantity of work for several different
work items
Super item calculation
A calculated quantity for a certain item is used several times
for determining the required quantities of several other
items
Detailed Cost Estimate
Quantity-Take-Off (QTO)
STEPS FOR AN ACCURATE AND EFFICIENT QTO
Measure everything as it shows
Never round off number, that are part of a
multiplication or division process before multiplication
or division is made
Round of the result of a multiplication or division
process to the nearest number of significant figures of
the smallest number
