3. QUANTITY SURVEYING.pptxgajanjsjsjjsjh

COLLEGE OF ENGINEERING TECHNOLOGY
DEPARTEMENT OF CIVIL ENGINEERING
Contract, Specification and Quantity Survey
(CENG 5121 )
QUANTITY SURVEYING
prepared byEDEN H.(MSC.)
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Quantity surveying is a term or processes used in the construction
industry to take measurements of civil works, prepare specifications,
and estimate the cost of works either for each trade of work or for the
whole project.
The following tasks are covered in quantity surveying:
1. Preparation of Specification and wbs
2.Taking measurements of civil works (Taking off quantities and
preparing BOQ)
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3. Preparation of approximate (preliminary) cost estimate at the
very early stage of the project
4. Preparation of detail cost estimate at different stages (taking as
built measurements/existing dimensions and conditions and
preparing payment certificates or approval of payment certificates
prepared by taking measurements)
5. Valuation of property
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PURPOSE OF QUANTITY SURVEYING
The purpose of quantity surveying hence the preparation of Bill of
quantities is:
I. Assist the client to have an accurate estimate of the volume of
work as well as the required budget.
II. To assist in the accurate preparation of tenders, by providing
uniform measurement of quantities.
III. To give an accurate checklist of work accomplished
IV. To assist in the certification of payments
V. To give insight into the required variation work amounts
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MEASUREMENT OF CIVIL WORKS
• Measurement of civil works includes the billing of each trade
of work either from drawings or the building itself for
defining the extent of works under each trade.
• The standard book, which is used in Ethiopia, is standard
technical specification & method of measurement for
construction of buildings by BaTCoDA, March 1991.
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Specification Worksheet (BOQ form)
It is the format which is used in a bill of quantity to list
(include) a short description of the specification along with its
measuring unit, quantity and unit prices to determine the total
cost for each trade of item.
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3.3 MEASUREMENT OF CIVIL
WORKS
THE PROCESS OF QUANTITY SURVEYING
There are four clearly defined steps in preparation of Bill of
Quantities:
1. Taking off
2. Squaring
3. Abstracting
4. Writing the final Bill of Quantity
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TAKING OFF
• This is the process of preparing /defining a detailed list of all
labor and materials necessary for the work and entering the items
on properly dimensioned paper.
• The standard form used for entering the dimensions taken or
scaled from drawings to determine the accurate quantity in each
trade of work, except reinforcement steel, is called Take Off
Sheet or Dimension Paper.
• The dimension paper used for taking off is usually double –
ruled as shown (A4 size).
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TAKING OFF
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Measurement of civil works
TAKING OFF
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3.3. MEASUREMENT OF CIVIL WORKS
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I. Taking Off
A separate sheet (Bar Schedule) is used to prepare
reinforcement
• quantities as shown below.
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The Process of Quantity Surveying
II. Squaring
 The dimensions entered in Column 2 are squared or cubed as the
case may be, multiplied by the timizing factor, and the result
entered in Column 3. This task is called squaring.
 All squared dimensions should be carefully checked by another
person before abstracting, and if correct the item should be ticked
with red. Use two decimal places.
III. Abstracting
 The squared dimensions are transferred to abstract sheets and all
similar dimensions are collected in the same category to obtain the
total quantity of each item.
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The Process of Quantity Surveying
Writing the final bill
 After the abstract sheets have been completed and checked, the
final bill of quantity is written.
 The dimensions are copied from the abstracts, and as each item
is transferred it should be ticked by a vertical line from the
abstract sheets.
 The description of each item in the final BOQ should be short,
precise and descriptive as per the specification.
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Measurement of Civil Works
BASIC PRINCIPLES OF TAKING OFF
 The following tasks are part of the Taking Off
 Describing the item,
 Bracketing (relating the description to the quantity),
 Timsing,
 Dotting on (adding to the timising factor),
 The Ampersand (ditto),
 Waste calculations,
 Deduction of items,
 Correction of dimensions (nullifying).
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TYPES OF TAKING OFF
 Mensuration (act of measuring)– the calculation of geometric
quantities such as length, area, and volume, from dimensions and
angles that are already known.
 Girth (perimeter) computation– linear measurement. There are
various methods of taking off quantities for computation of girth.
 In- to- in and out- to-out method – some wall lengths are taken out
to out and others in to in (offsets are added to out to out lengths) and
same are deducted from in-to-in lengths; used for any type of
measurement irrespective of condition of symmetry.
 Centre line method– suitable only when the cross sections of all
walls are symmetrical. In this method Centre line length is found and
same is used for taking off quantities (therefore only width and
depth vary).
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I. Taking Off
Types of taking off
Crossing method –lengths and breadths of walls as shown in plan
are taken for working out various items and this method is useful
only if the offsets of footings are symmetrical.
A. Out – to - Out and In – to – In Method
• Long Wall (Out – to - Out ) = Inner Length + 2 Times
Thickness of the Wall
• Short Wall (In – to – In ) = Inner Length - 2 Times
B. Center Line Method
• All dimensions are taken center to center
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C. Crossing Method
 Long Wall (Out – to - Out ) = Inner Length + 2 Times
 Short Wall (In – to – In ) = Inner Length
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Measurement of Different Works
I. Substructure
Any structure below the ground floor slab level including the
basement, retaining walls, ground slab, grade beam, and
foundation is called a substructure. substructure work
categorized as follows:
1. Excavation and earthworks
2. Concrete works
3. Masonry works
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1. Excavation and Earthworks
A) Site clearance:
• Removal of materials (including trees, bushes and the top 20 to
30 cm soil), any other obstruction from the site.
• A working space of 1m is required on each side.
• Clearing site vegetation is measured in m2 and embraces bushes,
scrub, undergrowth trees .
• Removal of trees is measured as enumerated item.
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B) Excavation (bulk excavation)
• Excavation to get reduced levels of every structural element
below the ground level is called bulk excavation.
• Working space for bulk excavation is 25 cm (not used for shallow
masonry)
• Depth of excavation less than 30 cm measured per m2 ,depth > 30
cm per m3
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C) Deep Excavation
• It is the actual excavation for the foundation and is measured in
m3.
D) Fill / Embankment
• Shall be measured in m3 of net volume to be filled. Fill is
required because the reduced level of every structural element
above the structure has to be covered.
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The subdivisions under fill are
Back fill: - filling by using the excavated soil but by removing
coarse particles.
Borrow fill: - filling by using fill material from another place
when there is shortage of fill or when better quality material is
required.
E) Disposal - cleaning the building area including cart away.
measured with m3
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2. Concrete Works
A) Concrete
Grades of Concrete
C5 - lean concrete, measured with m2
C15- for totally supported structural elements
C20- used for slabs; mix proportion is 1:2:4
C25- Commonly used structural Concrete; mix proportion is 1:2:3
C30-Used for chemical stores and nuclear plants
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B) Formwork – measured in m2
• Period of removal (minimum):
1. Vertical formwork to columns, walls and beams: 1-2 days
depending on the types of cement we used
2. Soffits formwork to slab: 21 days
3. props to cantilever slabs: 14 days
4. Soffits(under side) formwork to beams: 21 days
5. Props to cantilever beams: 14 days
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C) Reinforcement
The reinforcement bars are tied by ø6 mm or ø8 mm mild steel
wire and measured in kg.
3. Masonry Works
stone for below ground work shall be chiseled from natural stone.
• Stone wall is measured by volume, whereas stone pavement is
measured by area, by specifying thickness.
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II. Superstructure
1. Concrete works
a. Concrete - as discussed in substructure part
b. Formwork: Specify the type of material used and where
to use (zigba or steel) – m2
c. Reinforcement: Weight per unit length for Ф6 is 0.222
kg/m; for any other diameter d2, with weight per unit
length w2
32
w2 = (d2*2/162) * 0.222
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2. Masonry works
a) Stone masonry:-Measured by volume
b) Hollow and solid concrete blocks, measured by area
specifying the thickness.
 The standard thicknesses of HCBs are 10cm, 15cm, and
20cm.
c) Bricks masonry: measured by area specifying the thickness.
 Bricks are fire resistant, watertight and can also resist
compressive action of up to 50 MPa.
 The thicknesses of brick masonry are 25 cm (for double
layer) and 12 cm (for single layer)
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3. Measurement of Roof Structure
• The Unit of measurement for roof structure naturally falls between
enumerated items (trusses) and linear meters, (rafters and
purlins).
Measurement of Pitched Roof Coverings
• The area of roof coverings is unaffected by the inclusion of hipped
ends and valleys as long as the roof pitch remains constant
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Rainwater gutters and down pipes
• Rainwater goods completes the work associated with roof
coverings.
• Gutters and down pipes are measured in linear meters over all
fittings. The description should include reference to the type
of pipe or gutter, its nominal size, and the type, method
and spacing of fixings.
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• Fittings, such as running outlets, stopped ends, offsets and
connecting shoes, are enumerated and measured extra over
the pipe or gutter on which they occur.
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Measurement of Finishing's
• The term Finishing includes operations associated with
the completion of the floors, walls and ceilings of a
building. These are screeding, plastering, wall and floor
tiling, wallpapering and painting.
• The order of measurement of finishing on each floor will
normally be:
» Ceiling
» Walls
» Floors
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General rules of measurement
• Work to attached beams is included with ceiling finishes,
whilst work to attached columns is included with wall
finishes.
• Finishes to isolated beams and columns must be given
separately as should work in staircase.
• The principal unit of measurement for wall, floor and
ceiling finishes is m2. Where the width does not exceed
300 mm the unit of measurement is linear.
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6. Sanitary appliances such as sinks, wash basins, baths
and water closets.
7. Discharge pipes - waste, soil and vent pipes.
8. Any other work connected with the plumbing
installation.
Pipe work: Pipes are measured in linear meters over
all fittings and branches, stating the type, nominal
size and the method of jointing and fixing.
 Fittings are enumerated and measured as extra-over
the pipe work on which they occur.
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