Estimating, purpose and data required

What is estimating?

Estimating is the process of calculating, in advance, the quantities of the various items of work and the likely cost of a project from its drawings, specifications and current rates. The result, the estimate, is the expected cost before the work is done.

Why an estimate is prepared before construction

1. To know the probable cost, so the client can decide whether the project is affordable and worth doing.
2. To obtain administrative and financial approval and a budget. In Nepal, public work cannot start without an approved estimate and budget allocation (Public Procurement Act and Regulation).
3. To fix the cost estimate for tendering; bids are compared against it, and it helps judge abnormally low or high bids.
4. To prepare the bill of quantities and the quantities of materials, so purchase and storage can be planned.
5. To estimate the labour, equipment and time required, and prepare the work programme.
6. To control cost during the work and compare with the actual expenditure.
7. To decide the payment and fund flow, and to compare design alternatives.

Data required for an estimate

• Drawings: plans, elevations, sections, foundation and structural details, and schedules of doors, windows and finishes. Without complete drawings, quantities cannot be taken out.
• Specifications: the quality of materials and workmanship (for example cement mortar 1:4, M20 concrete, Fe 500 steel), so that the correct rate can be applied.
• Rates: the District Rate (published yearly by the District Rate Fixation Committee), the DUDBC norms for labour and material consumption, and local market rates for items not covered. Rates of materials, labour, transport (lead), and the contractor's overhead and profit are needed.
• Site data: site conditions, soil type, water table, distance of material sources (lead), and access.
• Quantities: the work quantities taken out item by item, using the units of IS 1200 / the Nepal standard methods of measurement.
• Other data: the applicable taxes (VAT 13%), contingency, price-adjustment and the contract conditions.