Monday, February 8, 2010

PREPARATION OF BQ n T-OFF

1.6-PREPARATION OF BILL OF QUANTITIES AND TAKING OFF SHEET
A bill of quantities is a document which lists all the items necessary for the complete construction of works. Each item includes a description and a quantity. When a contractor is asked to prepare a tender he is supplied with all the contract documents. Another reason for including BOQ/BQ (Bill of Quantities) in contract documents is that it provides the engineer with the opportunity of seeing how the contractors have arrived to their estimate.

1.6.1-Taking Off Sheet/Dimension Sheet
a) First Stage - Taking Off
Taking off - to calculate the quantity in each item of work. the taking off sheet, which is sometimes called a dimension sheet, is ruled in the following way; column A, column B, Column C and Column D, appear twice on each sheet.
  • Column A - called "timesing " column and is used if the quantity is to be multiplied for example if we were taking off the quantities for column bases and there were four bases, then 4/would appear in column A.
  • Column B - called dimension column and the dimensions of the item are entered one below the other in this column. Dimensions should always be entered in the following order, length, breadth, depth and thickness.
  • Column C - the squaring or cubing column, and it is where the final quantity is entered.
  • Column D is used for description of the item and for any additional calculations.
b) Second stage - Abstracting
It consists of transferring the description and quantity the description and quantity from the taking-off sheet to the abstract sheet (as shown in Appendix A2) and collecting together items, which can be, billed under one item. If the quantity has to be converted from one unit to another unit this is done on the abstract sheet.

c) Third stage - Writing a bill of quantities
There are certain principles, which should always be followed when writing a bill of quantities. It should be concise, accurate and well written (as shown in Appendix A3).

i) Descriptions
Each item should be described in enough detail to enable anyone reading the bill
of quantities to be able to locate the item in the works.

ii)Order

Items should be entered in a logical order. It is suggested that the following order be used.
  • Excavation - cubic, linear then square meter
  • Mass concrete and reinforced concrete - cubic, then square meters.
  • Reinforcement - largest diameter first
  • Brickwork - cubic then square items
  • Steelwork - nearest item first.

iii) Accuracy
It is usually necessary to re-measure civil engineering works when they are completed to determine the exact value of the work, and therefore it is not necessary to calculate the quantities too accurately when preparing the bill.

iv) Numbering
All items should be measured consecutively page by page.

v) Abbreviations
The following abbreviations are often used on the dimension sheets:
  • B'wrk - brickwork
  • C.I. - cast iron
  • Ddt - deduct
  • D.P.C - damp proof course
  • E.O. - extra over
  • Ex. - excavation
  • M.S - mild steel
  • n.e. - not exceeding
  • P.C. - prime cost
  • R.C. - reinforced concrete
  • S.G.S.W. - salt glazed stone ware
  • W.I. - wrought iron

1.6.2 Preparation of Bill of Quantities
The example of a bill of quantities for a river works contract for a new power station might contain the following ;
  1. Section A - list of principal quantities
  2. Section B - Preamble
  3. Section C - Day work schedule
  4. Section D - Work items
  5. Section E - Grand Summary

List of Section D-Work item:-
  1. Part 1 - General Items
  2. Part 2 - Demolition and site works
  3. Part 3 - Access roads
  4. Part 4 - Pipe work
  5. Part 5 - Dredging
  6. Part 6 - Pump chambers
  7. Part 7 - Circulating water ducts
  8. Part 8 - Wharf wall
  9. Part 9 - Jetty

Section A - List of Principal Quantities
The list of principal quantities being the main components of the works, with their approximate estimated quantities, so that tenderers obtain an overall picture of the general scale and character of the proposed works at the outset.
A list of principal quantities relaying to a reservoir as follows :-
Part 1 General Items
Provisional Sums
Prime Cost items

RM20,000
RM76,000
Part 2 Reservoir
Excavation
Concrete
Formwork
Steel reinforcement

1500 m3
12500 m3
6600 m2
150 tonnes
Part 3 Pipe work
Pipelines
Valves

850 m
22 no.
Part 4
Embankment
Filling


12000m3
Part 5
Access Road
Concrete road slab

1800 m3
Part 6
Fencing
Mild steel fence

1400 m

Section B - Preamble
The preamble in a civil engineering bill of quantities is to indicate to tendering contractors whether methods measurement other than the CESMM have been used for any part of works and whether any modification have been made in applying the CESMM to meet special needs where there are important practical reasons for adopting a different procedure.

Section C - Daywork Schedule
It is necessary to make provision for a daywork evaluation of work which cannot be assessed at bill rates. The CESMM provides three alternatives procedures.
  1. A list of the various classes of labour, material and plant for which daywork's rates or prices are to be inserted by the tenderer,
  2. Provision for payment at the rates and prices and percentage variations contained in the current federation schedules of daywork.
  3. The insertion of provisional sums in class A of the bill of quantities for work executed on a daywork basis comprising separate items for labour, materials, plants etc.

Section D - Work Items
  1. Prime Cost Items - Shall be inserted in BOQ under General Items (class A) to cover work carried out by nominated sub-contractors,
  2. Provisional sums - Shall be used to cover contingencies of various types and they can be entered in various sections of the BOQ for subsequent adjustment.

Section E - Grand Summary (total costs for the sections)

1.6.3 - The general formula for quantities

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