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Introduction to cost estimating Method of estimating •
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Unit method Floor area method Building Build ing vol volume ume metho method d Approximate Appro ximate quantity Bills of quantity Elemental cost analysis method
PRELIMINAR PRELIMIN ARY Y COST COST ESTIMA ESTIMATING TING
Introduction to Cost Estimating
Definition: “An estimate is an attempt to forecast the actual cost”
(Ostwald, P.F. (2001) A process to predict project costs and resources requirement. Estimating is a dynamic process. technologies, Factors considered in preparation of an estimate: current technologies, marketplace demands on materials and labours, quantities quantities of materials materials,, etc. experiences.. It requires a good data base of actual cost from past project experiences As the project evolves, more information becomes available – more accurate the estimations.
Introduction to Cost Estimating Variation in type of estimate with changes in project stages 1. Preliminary Estimate Identification
Appraisal Estimate Appraisal e g a t S t c e j o r P
Proposal Estimate Definition
Approved Estimate Approval
Pre-tender Estimate
Post-Contract Estimate
Implementation
Achieved Cost Operation
Introduction to Cost Estimating Preliminary estimate
An initial estimate at the earliest possible stages. It is likely that no design data will be available and that there will be only a crude indication of the project size or capacity. It is likely to be of use in the provisional planning of capital expenditure programme.
Appraisal estimate
Sometimes known as feasibility estimates. These are directly comparable estimates of the alternative schemes under consideration. An appraisal estimate should include all cost which will be charged against the project in order to provide the best estimate of anticipated total cost.
Introduction to Cost Estimating Proposal estimate
An estimate for the selected scheme. It is usually based on a conceptual design and design study specifications
Approved estimate
A modified version of the proposal estimate to reflect the client's views which intended to provide the basis for project cost control.
Pre-tender estimate
A refinement of approved estimate based on the definitive design work using the information provided in the tender documents which should be used during bid evaluation as a marker against which bids can be assessed.
Introduction to Cost Estimating Post-contract estimate
A further refinement to reflect the prices in the contract awarded.
Achieved cost
A record of the actual costs of the job in order to review performance and provide data for future projects.
3 types of estimates (in Malaysian Government)
Preliminary Detailed Abstract (PDA) – during design stage As Tendered Detailed Abstract (ATDA) – after tender is awarded As Completed Detailed Abstract (ACDA) – after completion of work
Methods of estimating Unit Method
The unit method is a single price rate method based upon the cost per functional unit of the building. This method is often regarded as a way of making a comparison between buildings in order to satisfy the design team that the costs are reasonable in relation to other buildings of a similar nature.
Building Types
Unit Cost
Hospital
Cost per bed space
Car parking
Cost per car parking lot
Hotel
Cost per room
School
Cost per pupil
Cinema
Cost per seat
Methods of estimating Unit Method
Total cost = cost per unit x number of units
Example: The current cost for a 100-bed hospital constructed is RM1,250,000. We are asked to estimate a 125-bed hospital. Solution: Cost per-bed = RM1,250,000/100 = RM12,500/bed New hospital cost = RM12,500/bed X 125 bed = RM1,562,500
Methods of estimating Floor Area Method
The method is a single price rate method based on the cost per square meter of the building. The use of this method should be restricted to the early stages of the design sequence. Total cost = cost per square metre x total building area
The rules for calculating the area: All length and breadth measurements are taken from the internal dimensions of external walls. No deduction is made for internal walls, ducts, lift shafts, stairwells, etc. – gross internal floor area.
Methods of estimating Floor Area Method
Example: A computer lab with 336 thick brick wall (measured from centre to centre). A similar computer lab was built with a price rate of RM850/m2.
336 thick Brick wall
Methods of estimating Floor Area Method
Solution: Floor Area
Total Cost
=lxw
= 402.64m2 x RM850/m2 = RM 342,244.00
= [42 - 2(0.336/2)] x [10 2(0.336/2)] = 41.664 x 9.664 = 402.64m2
Methods of estimating Building Volume Method
This method is generally used for multi-storeyed buildings. Total cost = volume of buildings x rate/ unit volume. The rules for calculating the area: All length and breadth measurements are taken from the external dimensions of external walls.
The rules for calculating the area (cont’d):
Building height is measured from the top of foundation to half-way up to the slope of pitched roof or 0.6m of the flat roof. Buildings with distinct types of occupation should have corresponding volumes assessed separately, for example, car park areas, shopping areas and office areas in a commercial building.
Methods of estimating Building Volume Method Sloped/pitched roof : c + b + a/2
Flat roof : a + b + 0.6m
Methods of estimating Building Volume Method
The rules for calculating the area (cont’d):
Height of building with parapet wall is measured from the top of foundation to the top of the parapet wall (without adding 0.6m)
Flat roof with parapet wall : c + d
Methods of estimating Building Volume Method
Example: A computer lab with 336 thick brick wall (measured from centre to centre). A similar computer lab was built with a price rate of RM120/m3. 336 thick Brick wall
Methods of estimating Building Volume Method
Solution: Volume
Total Cost
=lxwxh
= 2931.82m3 x RM120/m3 = RM351,818.40
= [42 + 2(0.336 / 2)] + [10 + 2(0.336 / 2)] + [1.20 + 4 +1/2(3)] = 42.336 x 10.336 x 6.7 = 2931.82 m3
Methods of estimating Approximate quantities
This method is regarded as the most reliable and accurate method of estimating, provided that there is sufficient information (such as drawings and specifications) to work on. One of the measurement rules is to group together items corresponding to a sequence of operations and relating them to a common unit of measurement. Composite rates are then built up from the data available for that sequence of operations.
Methods of estimating Approximate quantities Upper floor of a building is measured in m2 to include the following items: - concrete layer - damp proof membrane - floor finishes - reinforcement bar/fabric formwork etc.
Floor finishes Upper floor Damp proof membrane Reinforcement bar/fabric Lower ceiling finishes
Methods of estimating Bill of quantities It provides the most accurate estimate. All quantities for each work element will be measured and multiplied with price rate.
Item
Description
Unit
Qtty.
Rate (RM)
Total (RM)
A
Excavate trench for strip foundation not exceeding 1.50 m depth from formation (reduced) level and remove excavated material from
m3
325
1.50
487.50
Methods of estimating Bill of quantities Examples of building work elements in BQ: Substructure Piling Work Below Lowest Floor Superstructure Frame Upper Floor Roof Stairs External Wall Windows and External Doors Internal Wall and Partitions Internal Doors
Finishes Internal Wall Finishes Internal Floor Finishes Internal Ceiling Finishes External Finishes Fittings and Furnishings Services Sanitary Appliances Plumbing Installations Air Conditioning System Electrical Installation etc. External Work Earthwork Drainage
Methods of estimating Elemental Cost Analysis (ECA)
ECA can be defined as “a
systematic breakdown of the cost of a building to a client into the various building / construction elements in terms which are meaningful to both the client and the member of design
team.”
To enable the Design Team to determine how much had been spent on each building element.
To assess whether a balanced distribution of costs have been achieved amongst the various elements of the building. To provide comparison of costs of the same elements that may be used in different buildings. To obtain cost data for use in the cost planning for other projects.
Methods of estimating Elemental Cost Analysis (ECA)
ECA can be defined as “a
systematic breakdown of the cost of a building to a client into the various building / construction elements in terms which are meaningful to both the client and the member of design
team.”
To enable the Design Team to determine how much had been spent on each building element.
To assess whether a balanced distribution of costs have been achieved amongst the various elements of the building. To provide comparison of costs of the same elements that may be used in different buildings. To obtain cost data for use in the cost planning for other projects. ECA.docx
Methods of estimating Elemental Cost Analysis (ECA)
METHOD OF RELATING PROPOSED PROJECT TO ANALSYED EXAMPLE Elemental cost of external walls on proposed project: Analysed example
Proposed project
Total floor area 5,000m2
Total floor area 4,800m2
External wall area 4,000m2 Wall /floor ratio 0.80 Cost of external wall per m 2 of floor area (elemental cost) = RM37.50 Cost of external wall per m 2 of wall (unit cost) RM46.875
External wall area 3,600m2
Methods of estimating Elemental Cost Analysis (ECA)
METHOD OF RELATING PROPOSED PROJECT TO ANALSYED EXAMPLE Elemental cost of external walls on proposed project: UNIT COST METHOD 3600m2 of wall at $46.875 = $168,750.00 $168,750/4,800 = $35.156
PROPORTION METHOD Wall/floor ratio = 3600/4800 = 0.75 $37.50 x 0.75/0.80 = $35.156
(Total cost 4,800 x $35.16 = $168,768)
