What is the main function of BoQ (Bill of Quantities) ? How important the BoQ is?

The Bill of Quantities is a document compiled for construction projects in which all elements of material labor and plant needed to construct are itemized in detail, quantified and priced according to the Standard Systems of Measurement. Traditionally, it splits the work trades into groups known as Bills (e.g Earthworks, Masonry, Plastering, Tiling etc). The Bill of Quantities has the following uses:

1. Cost planning in the pre contract phase of the project

2. Tendering - An unpriced Bill of Quantities is sent out to bidders to price the work. The bidder with the lowest price normally wins (also based on other qualification criteria)

3. Interim valuation - The Bill of quantities will be the document that the client's/employer's Quantity Surveyor or Project Engineer will use to value the progress of work on site. 

Bill of quantities is important to estimate the use of material and as result get quotations and financing / cost of particular project for materials perspective.

Define quantities , specification and prices for each item of Project's Work Breakdown Structure

Knowlegde about qualtities. Can be Anything from Estimation of Quantities on Concrete reinforcements to Requirement of Shuttering Materials can be also called BOQ. Basic requirement is it will provide as a bench mark for all others say TIME,COST. Manpower required Etc. 

1. It demonstrates the detailed quantity , specification, and other requirements.
2. It can be used to derive the quantities of the various materials
3. it is one of the contract document
4. It plays the vital role in Traditional (item Rate) Contacts.

Contract BOQ is a breakdown of contract amount in terms of quantity and rates. When a project starts rolling the contractor start billing the employer based on BOQ and accomplishment of contracted work (interim payments).

BOQ rates are also used while evaluating Variations and Provisional Sums.

BOQ may also contain provisional sum, prime cost items to finalize at later stage of the contract.

The Bill of Quantities (BOQ) are prepared by specific field Quantity Surveyors to provide an extensive and itemized list which include but not limited to description of the item , quantity with the units.  It will be breakdown of all components or items under which construction project to be carried.

BOQ are prepared by the the follow of Standard Method of Measurement like in Qatar BOQ are being mustering in accordance of of CESMM3.

The main purpose of a Bill of Quantities is to itemise and define a project so that all tenderers are preparing their price and submission on the same information and at post contract stage help contractor to submit the progress works, control the activities and resources. 

BOQ helps in the preparation of Construction billing. Through BOQ, progress billing is done based on the work done for each portion as a percentage completed with the rates agreed to get the fiqure.

I believe BoQ is the core element for any project whether its Civil, Electrical, Mechanical or any other filed. If all the quantities worked out properly no further variation comes during the execution phase and hence more precisely project activities, procurement and overall project runs from start to end.   

Bill of Quantities serves as a basis of detailed breakdown of work scope with unit rates