Estimation & Costing of a project is the process of determination of quantities or costs of items of work and materials for completing the project. In other words, Estimation & Costing is a forecast of the project cost. An approximate cost of project work is the calculation of the quantities of various items of work, the cost incurred on the work. Furthermore, Estimation & Costing of a project is a close approximation of its actual cost.
So in this post, we will discuss the methods of calculating as well as preparing Estimation & Costing of a Project. In addition, the data’s required for framing Estimates and its types. The details about the Quantity Survey and Surveyor also their duties and controls, etc.
What is an ESTIMATION?
Estimation is the most important practical aspect of construction management. Moreover, it can be developed by using a combination of estimation methods. Moreover in Estimation, there are two important methods used in the construction process. They are as follows:
1. Quantity in Estimation & Costing
The term ‘Quantity’ in Estimation & Costing refers to the measurement of the drawings. For example: Plan, Elevation, Sections & Views.
2. Quality in Estimation & Costing
The term ‘Quality’ in Estimation & Costing refers to the specifications and properties of the materials, workmanship, transportation, etc. For instance: Weight, Density, Hardness of Materials, etc.
Data’s Required for Preparing Estimates:
- Measurement Drawings- Plans, Elevations & Section, View, etc.
- Specification of Materials- The class, nature, rates, name, model number as well as its specifications, properties, details, etc.
- Field Data- Topography of the site, Nature of the soil, Plinth height of the existing near buildings. Also, the site approach, water availability in the site, power supply, external sewerage facility, etc.
- Standard Drawings- Site Layout/ Master Plan, Floor Plans, Terrace Plan, Elevation, Section, etc.
- Plumbing Layouts & Specifications- Internal (Water Supply, Sewerage, Roof Rain Water Disposal) as well as External (Pump room, Water tank, Storm Water Disposal, etc) layouts of the building.
- Electrical Layouts & Specifications- Internal (Wirings, Fittings, Fans, AC, Control Panels, etc) as well as External (Transformers, Cable lines, Earthing wires, Area Lighting, Street Lights, Lifts, HVACs, etc.) layouts of the building.
- Landscaping/ Site Development- Boundary wall, Gate, Land Filling, Landscaping, Plantation, Drainage lines, Roads, etc.
Types of Estimates in Estimation & Costing of a Project:
1. Abstract Estimate
- Abstract Estimate is also referring to ‘Preliminary or Approximate Estimate’.
- This estimate is preparing the financial statement of the project which is based on practical knowledge and cost proposition.
- An abstract estimate prepares for all individual items. For instance- the cost of land, roads, plumbing, electrification works etc.
- Furthermore, this estimate along with a brief report explains the need and utility of the project. Also, the cost of individual items is preparing.
2. Plinth Area Estimate
- Plinth Area Estimate is also referring to ‘Rough Estimate’.
- The plinth area of a building means the area in which the building stands. Moreover, it is calculated by the construction area (length x width) excluding the offset i.e MOS (Marginal Open Space).
- This estimate prepares on the basis of the proposed area of the building.
- The Plinth area estimate is also calculated by multiplying the plinth area and plinth area rate of the building.
3. Cube Rate Estimate
- A Cube Rate Estimate is a type of Preliminary or an Approximate Estimate. In other words, it is preparing on the basis of the cubic content of a building.
- In addition, a cubic content of a building means that the plinth area is multiplied by the height of the building.
- The cubic rate estimate is more accurate than the plinth area estimate. In this estimate, the height of the building is also included.
4. Approximate Quantity Method Estimate
- The Approximate quantity method gives an approximate estimate based on the amount of building material. For example walls, foundations and plinth areas etc.
- In this method, the approximate total length of walls in a running meter is calculated and then multiplied by the rate of the running meter of a wall.
- For this method, the structure is also divided into two parts- the foundation with plinth and the superstructure.
5. Detailed Estimate
- Detailed Estimate is also referring to as ‘ Prime Cost’, ‘Bottom Up’ or ‘Grass Roots’ Estimating.
- Estimates that provide item-wise amounts of estimated work, unit rates and expenditure in construction are called Detailed estimates.
- The Detailed estimate is also an Accurate estimate. Furthermore, this estimate prepares for technical approval of the competent authority, arrangement of contract and execution of work.
- Detailed estimates prepare in two phases-
- Details of Measurements & Calculation of Qualities
- Abstract of Estimated Cost
- Factors uses in preparing Detailed Estimates–
- Location of the Site
- Local Labour Charges
- Drawings, Plans, Process Sheets, etc.
- Quality & Transportation of Materials
- Methods of taking out Detailed Estimates–
1. Separate & Individual Wall Method or General Method:
- Long-Wall Method
Long Wall Length Out-to-Out = Center to Center Length + Half Breadth on One Side +Half Breadth on the other Side = Center to Center Length + One Breadth.
- Short Wall Method
Short Wall Length In-to-In = Center to Center Length – One Breadth.
2. Center Line Method
This method is easy, quick and simple in calculations. In addition, the centerline method is suitable for rectangular, circular, polygon buildings.
6. Revised Estimate
A Revised Estimate is a type of Detailed Estimate. The revised estimate is also referring to as a ‘document‘. This document should also be accompanied by a comparative statement showing the variations of the objects of work. In addition, it gives the reason for the difference in the two cases for quantity, rate, increase and decrease or exceed and savings, etc.
The revised estimate prepares when one of the following conditions arises:
- When it exceeds the original accepted estimate or is likely to exceed 5%.
- When spending on work is also likely to exceed or exceed the amount of administrative approval by more than 10%.
- Even when there is a physical deviation from the original proposal, the cost can still be met by the agreed amount.
7. Supplementary Estimate
- The supplementary estimate is a fresh detail estimate of the additional functions. In addition to the original estimate.
- This approximation prepares when additional functions are required to complement the original functions. In addition, when development requires during the progress of the work.
8. Annual Repair & Maintenance Estimate (AR/AM)
- This estimate is designed to keep the structure work in proper order as well as in a safe condition.
- In the case of Buildings– White Washing, Doors & Windows Laminates, Paintings, Minor Repairs, Floorings, etc.
- In the case of Roads– Patch Repairing, Floorings, Filling & Maintenance of Culverts, etc.
Methods of Taking Out Estimation & Costing of a Project:
1. Center Line Method
The centerline method is appropriate when the structure or building has symmetric offset. In addition, the building is more or less rectangular in shape.
2. Crossing Method
In the crossing method, the length and width of the walls at plinth levels are taken (internal dimensions of the room + thickness of the walls) to calculate quantities.
3. Out-to-Out & In-to-In Method
This method is the most practical under all circumstances. Also, it uses in PWD for calculating the quantity or number of different items.
4. Bay Method
This method is useful and is generally observes in the case of a building which consists of several bays. It is calculated by the cost of the specific bay and then multiplied by the number of blocks in that building.
5. Service Unit Method
The estimation of the service unit method is to choose a standard unit of accommodation and multiply the estimated cost per unit. Moreover, this method uses in the project for design estimation and bid estimation.
- Schools- Cost per People
- Hospitals- Cost per Bed
- Roads- Cost per Kilometers
- Car Parking- Cost per Car Space
What is the Quantity Survey in Estimation & Costing of Project?
- Quantity survey is the survey of materials or objects used throughout the manufacturing process.
- In the quantity survey, a list of items or quantities is preparing during construction.
- Furthermore, it indicates that the quantity of work under each item is, given the price per unit of work, the quantity of the cost of that particular item.
- It also provides a list of each item used in the construction mentioned in the Estimate.
Who is the Quantity Surveyor in Estimation & Costing?
Quantity Surveyor is a qualified or experienced person who performs all the detailed estimation and construction costs, contract works related to the project. In addition, a Quantity Surveyor (QS) is a construction industry professional with expert knowledge of construction costs and contracts.
Duties of Quantity Surveyor-
- Preparing BOQ (Bill of Quantities)
- Preparing bills for the part payments during the various stages of the work.
- in addition, it also gives legal advice in case of disputes between the owner and the contractor.
- Preparing bills of Adjustments during the variations or any changes in the construction process.
Qualities of Good Quantity Surveyor-
- Quality surveyor’s should be well qualified and also well experienced in the construction sector.
- The surveyor should be able to read the drawings correctly i.e. plan, section, elevation, etc.
- The quality surveyor should also be able to produce a scheduled or a list of items and descriptions. They should also be able to read the bill of quantities accurately.
- They should also have in-depth knowledge of construction techniques, materials and various objects that are involved in the execution of the work.
Quality Controls in Estimation & Costing of a Project:
- Quality control is a process or a set of procedures, to ensure that the manufactured product or service performed follows a defined set of quality criteria and also to meet the needs of the customer or clients.
- It also includes techniques and activities of work that meet requirements for quality.
- Quality assurance is a process or procedures to ensure that a product or service under development meets specified requirements.
- Also, in Quality Control various Tools & Techniques are includes. They are as follows:
- Cause & Effect Diagram
- Control Chart
- Flow Chart
- Run Chart
- Scatter Diagram
- Pareto Chart
- Statical Sampling
- In addition, these tools and techniques can help in three conditions:
- Project is meeting the quality standards
- Moreover, it provides a basis for corrective actions
- Also, provide feedback about the quality assurance process
Quantity Controls in Estimation & Costing of a Project:
- Quantity Control is the key element in ‘Project Control’.
- In other words, Quality control is a group, employee, or organization similar to scheduling, cost, procurement or contract administration tasks.
- It also has a major impact on the Project schedule.
- Moreover, it uses standards that are based on data collected through task measurement.
- Several techniques are also used to control fluctuations in work volume. For instance-
1. For Large Projects-
- Employee Overtime
- Temporary Help
- Cycle Billing
- Floating Work Unit
- Part-Time Help
2. For Small Projects-
- Work backlog
- Project Maintenance
Quantity Controls Techniques in Estimation & Costing:
- Total Inspections
- Statistical Quality Control
- Spot Checking
- Zero Defects
ESTIMATION & COSTING OF PROJECT PDF
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Frequently Asked Questions
1. Abstract Estimate
2. Plinth Area Estimate
3. Cube Rate Estimate
4. Approximate Quantity Method Estimate
5. Detailed Estimate
*Quantity survey is the survey of materials or objects used throughout the manufacturing process.
*In the quantity survey, a list of items or quantities is preparing during construction.
*Furthermore, it indicates that the quantity of work under each item is, given the price per unit of work, the quantity of the cost of that particular item.
*It also provides a list of each item used in the construction mentioned in the Estimate.
2.Specification of Materials
5.Plumbing Layouts & Specifications
6.Electrical Layouts & Specifications
7.Landscaping/ Site Development