A correct approach to estimate


The construction evaluation work entrusted to a contractor by the owner furnishes a bill of quantities if he intends to get an offer from the tenderer on an item rate basis.

The client prepares such a bill of quantities by extracting those items from the sanctioned evaluation which is proposed to be entrusted to a contractor. The tenderer will quote his rates against the items on the bill of quantities.

Estimate infrastructure

Contractor’s bill

The tenderer will, however, prepare his estimate bill of quantities, which form the basis of his offer, and later assist him in planning, scheduling, and constructing of the work. Programme of Work: As a prerequisite to preparing the contractor’s bill of quantities, he/she should:

  1. study the tender documents carefully.
  2. visit the site of work and collect detailed information that will help him in preparing the evaluation bill of quantities.
  3. prepare a tentative construction programme. This programme shows the principal items of construction, the duration required by them, and the scheduled dates of their start and completion. Such a programme is of considerable help to inaccurate pricing of material, labour, plant, and equipment, scaffolding, etc.
Evaluation construction

Important divisions of the contractor’s bill of quantities are as below:

1) Contractors’ Work

Many contractors carry out only certain items of work by employing their labour. The contractor should identify these items. He should then build up the rate for the unit item, considering materials, labour, and plant equipment. The items should be priced based on these rates.

2) Work by the Sub-contractor

The contractor entrusts certain items of the work to his sub-contractors after obtaining the client’s approval. The contractor gets the subcontractor’s bids, selects the most competitive bid. To this, he adds his expenses and profit, Supervision, and any other reason and adds the total amount in his bill of quantities.

3) Nominated Sub-contractor and/or Supplier

The contractor has to get a certain portion of the work by a sub-contractor nominated by the owner and/or get certain materials from suppliers nominated by the owner. They include these items under provisional sums or prime cost sums. The contractor has to add to the work he has to do in connection with these items such as unloading, handling, storing, fixing, supervision and his margin of profit.

4) Insurances

It required the contractor to ensure the works against potential damage due to fire or other risks. Such insurances have to be priced as per the requirement of contract conditions.

Besides, the above provision has to be made for the following.

  1. transport to and from the site; erection and dismantling of large plants and equipment.
  2. Scaffolding.
  3. Setting out works.
  4. Watch and ward.
  5. Providing and maintaining access roads to the site as long as facilities like offices, stores, canteen, roads, and portable toilets in the works area.
  6. Lighting and water and power.
  7. Bailing out water.
  8. Telephone facilities.
  9. Expenditure on hospitality.
  10. Any other related expenditure.

All the expenses discussed above total up to the cost, which the contractor will have to spend on the construction work. Besides the profits, the contractor will arrive at the price he can offer to the client.

1 comment on “A correct approach to estimate
  1. Angus Jenkins says:

    Good post!

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