Billing of Quantities (BOQ)
Bill of Quantities also referred to as BOQ, is a document
formulated in the construction industry to specify materials, labors, and their
cost. It serves as a communication tool between client, consultant & the
contractor. It is usually prepared by a cost consultant or a surveyor.
Primarily there are two types of BOQs
Bill of Materials
Bill of Labour
Basic Format for preparing BOQ
The main sections included in the bill of quantities are
Form of Tender, Information, Requirements, Pricing schedule, Provisional sums,
and Day works. For the preparation of BOQ, 5 main components are to be
considered which are as follows:
Taking off Quantities:
Taking off is the process of analysing the drawing and its
specifications to identify the elements required for the preparation of BOQ.
Description:
In this step, the appropriate narrative of a particular work
is provided to explain and justify the work being done.
Working Up:
This step includes recording every measurement required into
a sheet called the TDS Sheet. The times column (multiplier column) is for
filling up the number of repetitions of the same work. It depicts the factor of
multiplication. Dimension column is the one where all the dimensions like
length, width & depth are recorded. Whereas in the Sums column we simply
multiply the previous elements (Multiplication factor x Dimension) to get the
total quantity of the work.
Calculation of materials for Reinforced Concrete
Construction
Materials requires for reinforced concrete are cement, sand,
coarse aggregate and steel. Let us assume a standard quantity of 1m3 Cement
mortar and a mix proportion of 1:1.5:3 (1 part Cement, 1.5 parts Sand & 3
parts CA). The quantity can preferable calculated by two methods, which are
weight & volume method.
Let us consider the volume method for reinforced concrete
construction. Dry volume of total materials is equivalent to 1.54 times the
volume of wet concrete. Hence let us take the quantity of cement mortar as 1.54
m3.
Quantity of cement
The formula to calculate the volume of cement is as follows:
(1.54×1)/(1+1.5+3)=0.28 m^3
Since the cement is available in bags, volume of 1 cement
bag is 0.0347 m3.
0.28/0.0347=8.07 bags of cement
Quantity of sand
Formula to calculate volume of sand is as follows:
(1.5×1.54)/(1+1.5+3)=0.42 m^(3 ) of sand
Quantity of Coarse aggregates
To calculate volume of CA is as follows:
(3×1.54)/(1+1.5+3)=0.84 m^(3 ) of CA
BOQ of Steel reinforcement
Percentage of steel reinforcement usually depends on the
type of components used. The values of percentage of steel differ from
structure to structure. Some of which are mentioned below:
Slabs = 1.0% of concrete volume
Beam = 2 % concrete volume
Column = 2.5% of concrete volume
RCC roads = 0.6% concrete volume
Assuming 2.5% as the steel reinforcement required, the
formula to calculate steel is:
2.5/(100×1)×7850=196.25 kg
Estimation of labour for reinforced concrete
The requirement for labour as per the specified quantity of
work is as follows:
Mason – 0.37 day
Bar bender, per 100 kg of steel – 1 day
Mixer operator – 0.0714 day
Vibrator Operator – 0.0714 day
An additional contractor’s profit and sundries may be
included. It generally differs according to place, organization and work. It
ranges from 10 – 20%. In this case, assume 10% of total cost of materials,
labour and equipment for contractor’s profit and 7% for sundries.
As we write down the brief description of each work to be
completed in a particular project, we can simultaneously assess the issues and
obstacles tagging along with it. These obstacles can be tackled beforehand and
thus saving time, energy and resources. Companies often outsource estimating
companies to prepare BOQ for massive project as second layer of review to
validate in-house estimates.
Comprehensive Planning of the
Project
Once the initial project budget is laid down after taking
into consideration the drawing & specifications, the planning of the
project becomes much simpler. It will furnish a complete & comprehensive
picture of the equipment and material necessary and helps the engineers
involved in the project to quote for the work suitably.
BOQ Eliminates Guesswork
BOQ simply eliminates any scope of guesswork in the entire
process of project construction. In the paucity of BOQ, the quotes of each work
needs be worked out separately and independently only on the basis of
guesswork. It withholds everything transparent, hence there is zero chance for
corrupt practices by the tenderers or the contractors.
Saves Time & Cost of
Construction
If the materials are available on time according to the
specifications mentioned in the BOQ, the time of construction can be minimized
effectively. It also gives fair amount of time to compare the prices of all the
materials and choose the best rate. Thus saving the cost of construction.
Limitations of Bill of
Quantities
Bill of Quantities should be prepared according to a
standard methodology. Otherwise, chances of errors substantially increases. The
errors that could possibly occur during the BOQ process are incorrect
measurement of the quantities, arithmetic errors, errors due to various changes
made during the project, incorrect assumptions, counting the same item twice or
omitting an item, and ignoring the change in currencies or units.
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