Quantity Survey & Estimation – Lecture # 1

Table of Content

• Introduction to Quantity Surveying & Estimation
• Methods of Estimations

Main Items of Work

• • Earthwork
• Concrete In Foundation
• Damp Proof Course
• Masonry
• Deduction For Openings, bearings Etc,
• R.C.C Works

• Flooring And Roofing
  • Ground Floor
  • 1st Floor And 2nd Floor
  • Roof
  • Floor Of Door Sills
• Plastering And Painting
• Pointing
• Pillars
• Door And Windows
• Wood Work
• Iron Work
• White – Washing Or Color – Washing Or Distempering
• Painting
• Lump Sum Items
• Other Items
• Electrification And Sanitary And Water Supply

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Quantity Survey & Estimation – Lecture # 1 – Excerpt

Quantity Survey & Estimation

Course Instructor

Engr. Shad Muhammad

Lecturer, Department of Civil Engineering

Qurtuba University of Science & IT, D. I. Khan.

Quantity? Survey? And Estimation?

What can be wp-wp-includessd in quantity?

Can civil structures estimate be exact?

What about unknown features or contingencies?

What is estimated cost?

Probable cost of construction—-Estimated Cost

Is quality of work a part of quantity survey?

What if estimate exceeds available money?

You have 2 options to reduce the cost:

1. Reduce the amount of work
2. Change the specification

Amount of work controls the quantity of work.

Specifications controls the quality of work.

How and from where to take quantities?

1.Plans

2.Elevations

3.Sections

Data Required for the Preparation of an Estimate or Quantity Survey

1. Drawings: Complete and fully dimensioned drawings (i.e. plans, elevations, sections and other details) of the building or work in question are required.
2. Specifications: Detailed specifications, giving the nature, quality and class of work, materials to be used, quantity of the material, their proportions, and method of preparation are required.
3. Rates: The rates of various of work, materials to be used in the construction, wages of different categories of labor (skilled or unskilled) and cost of transportation charges should be available for preparing an estimate of work cost.
4. Actual Finished Work: Quantities can be calculated from the actual work done in the project site.

Quantities Calculation

The quantities mainly can be calculated as:

Quantity = Length × Width × (Height or Thickness) = Volume

Quantity = Area of cross-section × Length = Volume

Quantity = Length × Width = Area

Quantity = Length

Quantity = Number of Units

Quantity = Weight

Advices?

Learn to read drawings in detail.

Learn to link plans with sections and elevations, etc.

Try to work on visualization of hidden features of the structure.

Start from simple to advanced drawings.

In preparing an estimate, items are usually classified and grouped sub-head wise, but for beginners it is convenient to make up the items in the same order, as far as possible, as they would be executed or constructed.

Metric System and Units

Very simple as units are multiples of ten or one-tenth of the other.

Produce simplification in calculations.

FPS [Foot (ft), Pound (lb), Second (s)] System works on fractions which make it difficult.

Arithmetic operations should be well commanded for this subject.

Metric System and Units

Conversion Examples:

1 km=1*103 m = 1000 m

1 kg =1*103 g = 1000 g

1 milliliter = 1*10-3 l = 0.001 l

Units for Civil Engineering Works

.

System International (SI) Units

.

Method of Estimating

Estimated Cost:

Probable cost of the construction.

It is known at initiation of work. (Project Initiation)

Actual Cost:

Account of all expenditure is maintained day-to-day during execution of work in the account section and at the end of the completion of work. And when the account is complete, actual cost is known. 

The actual cost is known at completion of work. (Project Closure)

Remember: The actual cost should not differ much from the estimated cost worked out at the beginning.

Cost at Project Initiation = Cost at Project Closure

Method of Estimating

Detailed Estimate:

Preparation of detailed estimate consists of working out the quantities of different items of work and then working out the cost.

Estimate is prepared in 2 Phases:

1.Details of Measurements and Calculation of Quantities: The whole work is divided into different items of work as earthwork, concrete, brickwork, etc. and the items are classified and grouped under different sub-heads, and the details of measurement of each item of work are taken out and quantities under each item are computed in prescribed form-Detail of measurement Form (shown below).

Method of Estimating

2. Abstract of Estimated Cost: The cost under item of work is calculated from the quantities already computed at workable rate (Market Rate), and the total cost is worked out in a prescribed form, Abstract of Estimate Form (shown below).

A percentage of 3 to 5% is added for contingency, to allow for petty expenditures, unforeseen expenditures, changes in design, changes in rates, etc. which may occur during execution of work.

A percentage of 1.5 to 2% is also added to meet the expenditure of work-charged establishment.

Main Items of Work

1.Earthwork

2.Concrete In Foundation

3.Damp Proof Course

4.Masonry

1.Deduction For Openings, bearings Etc,

5. R.C.C Works

6.Flooring And Roofing

A.Ground Floor

B.1st Floor And 2nd Floor

C.Roof

D.Floor Of Door Sills

7.Plastering And Painting

Main Items of Work

8.Pointing

9.Pillars

10.Door And Windows

11.Wood Work

12.Iron Work

13.White – Washing Or Color – Washing Or Distempering

14.Painting

15.Lump Sum Items

16.Other Items

17.Electrification And Sanitary And Water Supply

Main Items of Work

1. Earthwork:

In excavation and filling.

Calculated in m3 (L*B*D).

Foundation trench are usually dug to the exact

  width of the foundation with vertical sides.

Filling of trench after laying foundations are not taken into considerations mostly.

If trench filling is accounted, this may be calculated by deducting the masonry / foundation from excavation.

Earthwork in plinth filling is calculated by taking the internal dimensions in between plinth-wall (L*B*D).

Thickness of concrete in floor usually 7.5cm (3’’) must be deducted from plinth filling calculations.

If sand filling is done in plinth, then separate calculations should be taken. [Extra earth separate calculations]

Main Items of Work

2. Concrete in Foundations:

(L*B*H) = m3

L*B of foundation concrete is same as for

  excavation. Only depth and thickness differs.

Thickness of foundations concrete varies from (20 cm to 45 cm), usually 30 cm or (9” to 18”) usually 12”.

Foundation concrete usually consists of lime concrete or weak concrete.

Cement : Sand : Coarse Aggregate =  1:4:8 or 1:5:10

Main Items of Work

3. Soling:

Computed as (L*B*t) = m3

When the soil is soft or bad, one layer of dry brick or stone soling is applied below the foundation concrete.

Main Items of Work

4. DPC: Damp Proof Coarse:

Computed as (L*B) = m2

Usually, 2.5 cm (1”) thick rich cement concrete (1:1.5:3)

or

2cm (0.75”) thick rich cement mortar (1:2) mixed with standard waterproofing material is provided at plinth level to full width of the plinth wall.

1 kg of CEM-Seal or Impermo per bag of cement is used.

Main Items of Work

5. Masonry:

Computed as (L*B*H) = m3

Foundation & plinth masonry is taken under one item & masonry in superstructure is taken under separate item.

In storied building, the masonry in each storey as ground floor, first floor, etc are computed separately.

In taking out quantities the walls are measured as solid & then deductions are made for openings as doors, windows, etc.

Masonry of different classes, masonry with different mortar, etc are taken out under separate item.

Arch masonry is taken separately.

Main Items of Work

5. Masonry:

Splayed or rounded sides of wall are taken as rectangular & extreme dimensions are taken to find out the quantities.

Thin wall partitions are measure in m2.

Honey combed brick wall is taken under separate item in m2. No deductions are made for holes.

Stone masonry is calculated in same manner as bricks.

Main Items of Work

6. R.C.C Work:

May be in roof slab, beams, lintels, columns, foundations, etc.

Computed in m3

Bearings are added with the clear span to get the dimensions.

Quantities are computed in m3 exclusive of steel reinforcement and its bending but inclusive of centering and shuttering & fixing and binding of reinforcement.

The rebars including bending is taken up separately under steel works in quintals. [1 quintal = 100 kg]

The volume of steel is not to be deducted from R.C.C work.

Centering and shuttering (formwork) are usually wp-wp-includessd in the R.C.C work, but may be taken separately in m2 of surface in contact with concrete.

Main Items of Work

6. R.C.C Work:

In absence of detailed design, the percentage

  of steel reinforcement is taken as:

Main Items of Work

7. Flooring & Roofing Work:

1. A) Ground Floor:

The base lime concrete & floor finishing of cement concrete or stone or marble or mosaic, etc are usually taken as one item and computed in m3

The ‘L’ and  ‘B’ are measured as inside dimensions from wall to wall of superstructure.

Both base concrete and floor finish are paid under one item.

Main Items of Work

7. Flooring & Roofing Work:

1. B) 1st Floor, 2nd Floor, etc:

Supporting structures is taken separately in m3 as R.C.C and the floor finish is taken separately in m2 as 2.5 cm or 4 cm (1” to 1.5”) cement concrete or marble or mosaic, etc.

If a cushioning layer of lime or weak concrete is given in b/w slab and floor, the cushioning concrete may be measured with the floor under one item or taken separately.

Main Items of Work

7. Flooring & Roofing Work:

1. C) Roof:

Supporting structures is taken separately in m3.

The bearing of the roof or floor slab is given as the same thickness as the slab usually 10 cm or 15 cm (4” to 6”).

In case of Tiled, Galvanized Iron Sheet (G.I Sheets) or Asbestos Cement Sheet roofing are taken out in m2 & measured flat including overlaps with all fittings & supporting trusses & members are taken out under separate item.

Main Items of Work

Main Items of Work

8. Plastering & Pointing:

Plastering usually 12 mm (1/2”) thick is calculated in m2.

For walls, the measurements are taken for the whole face of the wall for both sides as solid & deductions are made for any openings.

Plastering of ceiling usually 12 mm (1/2”) is computed in m2 under separate head as this work is done with rich mortar.

Thin rich cement mortar plastering in R.C.C work may also be taken under a separate item, specially in the ceiling inside room.

Main Items of Work

10. Cornice:

Ornamental or large cornice is measured in running meter (rm) or running foot  (rft) for the complete work including masonry, plastering, moulding, etc & paid in r/ft or r/m.

Main Items of Work

11. Pillars:

Pillars are taken separately in m3 for their net volume & quantities are calculated by correct geometrical measurements by simple measurement method.

Plastering of pillars are calculated in m2 multiplying the circumference of perimeter by the height.

Quantity = X-Sectional Area * Height

Main Items of Work

11. Pillars:

Main Items of Work

12. Doors & Windows:
13. A) Chowkhat or Frame:

Door & window frames or chowkhats are computed in m3.

Length is obtained by adding the length of all the members of the chowkhat, top and two verticals if there is no sill member.

And add the bottom if sill is present. And this length is multiplied by the two dimensions of the x-sec of the member.

If there is a horn projection these projections also should be added to length.

If there is no sill member, vertical members should be inserted into the floor by about 2.5 cm to 4 cm (1” to 1.5”).

Main Items of Work

12. Doors & Windows:
13. B) Door / Windows / Shutters:

Computed in m2 (B*H).

A clearance of 6 mm (0.75”) may be allowed at the bottom of door if there is no sill member.

But for measurement of payment, the clearance should be taken into account.

The name of timber used, the thickness of the shutters, type of shutters & the nature of fittings (iron, brass, etc.) should be noted in the item.

Fittings are computed in numbers.

Fittings may also be wp-wp-includessd in sq. m rate of shutters.

Hold fasts are taken separate, under separate item by weight or by number.

Main Items of Work

12. Doors & Windows:
13. C) Door / Windows / Shutters:

Wooden beams, posts, wooden roof trusses, chowkhats, etc. come under this item and the quantities are computed in m3.

Main Items of Work

13. Iron Work:

Computed in weight in kg or quintal & the quantities are calculated by multiplying running meter by the length.

The weight per running meter can be obtained from the steel section book.

For steel joint, the length is equal to the clear span + 2 bearings.

Density of mild steel = 7850 kg/m3 or 78.5 q/m3 or 490 lb/ft3.

The weight of bolts, nuts & rivets with heads can be calculated by counting there numbers & sizes & consulting steel tables.

For steel roof truss, 5% of the steel work is usually provided for rivets, bolts & nuts.

Main Items of Work

14. White-Washing or Color Washing or Distempering:

Quantities computed in m2.

No. of coats of white washing or coloring are taken as one job or work and the rates cover for the number of coats which should not be a multiplying factor.

The no. of coats should be mentioned in the items list.

Deductions are dealt in the same manner as for plastering.

Other type of surface finish are done similarly.

Main Items of Work

15. Painting or Varnish:

Painting or varnishing of doors & windows are computed in m2.

The dimensions are the outer dimensions of doors & windows.

The area is measure flat (not girthed).

No separate measurement is taken for the chowkhat, as area is same as the area of wall openings.

For iron bars, grills, etc. the area of the clear opening inside the chowkhat is taken.

For beams, rafters, purlins, posts, etc. the timber or iron, the area of actual exposed surface is taken for painting.

Main Items of Work

16. Lump-sum Item:

Sometimes, a lump-sum rate is provided for certain small items for which detailed quantities cannot be taken out easily or it takes sufficient time to find the details.

For example: As front architectural or decoration work of a building, fire place, site cleaning & dressing, etc.

Main Items of Work

17. Electrification & Sanitary & Watersupply Work:

For sanitary & water supply work 8% & for electrification 8% of the estimated cost of the building work are usually provided in estimate.

Deductions

Deductions

Rates

Rates of different items in the estimate are the current rates for the completion of the items of work which wp-wp-includess supply of material, transport, labor, scaffolding, overheads, contractors’ profit, taxes, etc.

The rates are usually taken from “Schedule of Rates or Market Rates”.

Degree of Accuracy in Estimating

Depends upon rate of item and the unit of payment.

Higher the rates, the greater should be the accuracy with which the quantities are calculated.

Where rates are high & paid per unit, dimensions should be absolutely correct, though taking dimensions to the nearest 1cm to 0.5cm (1/2” to ¼”) may be allowed for practical purposes.

The quantities in such cases should be worked out to 2 decimals.

In case of wall, where masonry is paid in m3, a few cm added to or subtracted from the length or height would put little effect on total content.

But if the width or thickness of the wall where every half cm or quarter affects the results considerably.

Principle of Units for Various Items of Work

Mass, voluminous & thick works shall be taken in cubic units or volume.

Shallow, thin & surface works shall be taken in square units or in areas.

Long & thin work shall be taken in linear or running units.

Piece work, job work, etc shall be taken in numbers.

Brick Sizes

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