What is an Estimate?
An estimate is the expected or probable cost of work and is generally prepared before the construction’s execution.
For the construction of all engineering works, it is essential to know the probable cost of construction for the complete work previously that includes labour cost, material cost, transportation cost, scaffolding cost, tools and plants cost, water cost, taxes, charges for supervision and establishment and contractor’s profit.
If the above estimated probable cost is higher than the available fund, exercises are performed to reduce the cost by changing the specifications or reducing the work.
For preparing an estimate, the quantities of several work items are determined by straightforward mensuration systems, and from these quantities, the cost is computed.
The calculations mainly consist of (length x breadth x height) or ( length x breadth) or ( height/thickness).
Hence an estimator has to go into details of each item, whether big or small by imagining building or structure, etc. from the study of drawing and specifications.
Accuracy in the estimate is essential; otherwise, it is difficult to arrange for additional money if the expenditure exceeds the estimate.
The rate of each item should be reasonable and preferably the present market rate.
Importance of Estimating
- An estimate helps to determine the approximate cost of works before their execution; thus, we can know whether the work can be completed according to given specifications within a specific budget.
- It is needed to invite tenders for the work and to prepare a contract for the project.
- An estimate helps to check the work performed by contractors during and after execution. Contractor’s payment is also made per the present measurements by examining the already made calculations for each work item.
- It provides an idea for the necessities of controlled materials like cement, steel, and brick, etc.
- A complete estimate helps to advise the client on the following.
- Properties Valuation based on land and building for purchase, sale, and mortgage, etc.
- Standard rent Fixation
- On a cover note regarding fire insurance
- The sale price of flats in case of the building being constructed on an ownership basis.
- On an arbitration proceeding to claim the reasonable amount of building.
Data Needed for the preparation of an estimate
Fully complete dimensioned drawings, i.e., plan, sectional elevation, section, and other details.
The detailed specification provides work nature, quality and class, materials to be used in different parts of work, material quality and proportion, preparation method, workmanship, and work’s execution description.
The rates of the different work items, construction materials, and the labour wages of various categories (skilled or unskilled) should be available for making an estimate.
Sanctioned SOR (Schedule of rates) should be followed, or the rate may be calculated by the rates analysis method.
After collecting the above information, the estimate is then worked out under various sub-heads of work, and the quantities/cost under each sub-head are then worked out.
Factors to be viewed for the preparation of detailed estimate
Following factors should be examined while preparing the detailed estimate.
Quantity of materials
For large works, many materials are required; the same can be purchased at a cheaper than the rate of a smaller quantity of materials. So the rate should be framed out according to the volume of the work.
Availability of the materials
The estimated cost of work will be higher if the materials required are not available as and when required, the workers and supervisory will remain idle due to this. It will also affect the work progress. So it should be assumed that the materials required for the execution of work should be available at the worksite as and when required.
Transportation of materials
The cost of transportation of smaller quantities of materials will be more than the cost of transportation of a large number of materials bought at a time.
Location of site
Suppose the worksite is located at an old place where frequent loading, unloading is necessary several times. Due to different modes of transport, damage or loss of materials should be considered carefully.
Availability of labour
Daily wages of local labour should be considered before the preparation of an estimate, as for as possible local available labour should be engaged.
Procedure For Building Estimation
Before Calculating the quantities of different items, you must read the drawing thoroughly and correctly.
- The dimension of each room
- Schedule of openings
- Work Specification
- Wall Thickness
- Foundation Type and its details
- Stair Details
Prepare Quantity Sheet or Building Estimate Format
Sample of quantity sheet for estimation is as follows.
Calculation Of Quantity of Different Items
Now you have to calculate the quantities of different items from their length, width and height/depth. By multiplying length x breadth x height you will get the quantity in cubic meter (If dimensions are in meter) and by multiplying ( length x breadth) or ( height/thickness) you will get the quantity in Square meter ( If dimensions are in meter).
- Depth for excavation is considered from the bottom of PCC to ground level.
- Trench size is considered greater then footing size due to working space for labours. Here in the above quantity sheet footing size is 1meter × 1 meter and we have considered 0.3 meters extra for working area.
Building estimate In Excel Sheet