Test: Estimation and Costing- 1 - Civil Engineering (CE) MCQ

While preparing an estimate it is not possible to work out details of Petty Items (insignificant with respect to civil engineering) hence their lumpsum value is considered. Following are Items and their lumpsum cost:

• Contingency = 3% to 5% of project cost
• Work Charge Establishment = 1.5 - 2% of project cost
• Tools and Plants = 1% - 1.5% of project cost
• Departmental Cost (Engineering cost) = 10 - 15% of project cost
• Sanitary and Water Supply = 8% of project cost
• Electrification = 8% of project cost

As per IS 1611:1972 "CODE OF PRACTICE FOR APPLICATION OF CEMENT AND CEMENT-LIME PLASTER FINISHES"
Recommeded plaster specifications:

The various units of measurement of earthwork are:

• Surface Excavation:  Excavation exceeding 1.50 m in width as well as 10 m2 in the plan but not exceeding 30 cm in depth shall be described as ‘Surface Excavation’ and measured in square meters.
• Surface dressing: Trimming of natural ground, excavated surface, and filled-up area to remove vegetation and/ or small inequalities not exceeding 15 cm deep shall be described as surface dressing and measured in square meters.
• Excavation in trenches for foundation and for Pipes Cables etc: Excavation trenches for foundation and for pipes, cables, etc. not exceeding 1.50 m in width and for shafts, wells, cesspits, and the like not exceeding 10 m2 on plan – and shall be so described and measured in cubic meters.
• Rough Excavation: Excavation not requiring dressing of sides and bottom reduction to exact levels such as winning earth from borrow pits, hillside cutting, etc. shall be described as rough excavation and measured in cubic meters.
• The other type of excavation except as mentioned above is measured in cum.

Center line method
In this method of estimation, the total centerline length of walls in a building is first calculated, then the center line length is multiplied with the breadth and depth of the respective items to get the total quantity at a time.
Deductions
L Junction - There is no need to deduct from total centreline length.
T Junction - Half (1/2) breadth wall measurement should be deducted for a T junction.
Calculation:
Estimate be central line method is as follows:
[(4+0.1+0.1)×2] + [(3+0.1+0.1)×2] = [8.4] + [6.4] = 14.8 m 

Concept:
Lift of material:

• It is the vertical distance calculated from the ground level up to which the laborers have to excavate the soil and remove it for the standard rate.
• It is the average height through which the earth has to be lifted from source to the place of spreading or disposing.

Calculation:

The lift of soil material for the canal = (1.50+1.20)/2 = 1.35m

Explanation:

The given proportion 1:2:4 is by volume with 1 part being cement, 2 parts being Fine aggregate and 4 parts being coarse aggregate.
Total wet volume of concrete = 10 m³
Dry volume of concrete should be taken to be 50 % more than its wet volume.
∴ Dry Volume of concrete, V = 1.50 × 10 = 15 m³
The volume of coarse aggregate, = proportion of coarse aggregate × dry volume /total proportion
Or
Volume of coarse aggregate, V_CA = 4 × 15 /(1 + 2 + 4)
V_CA = 8.5 m³
In a similar manner, the volume of fine aggregate and cement required can also be estimated.
V_FA = (2/7) × 15 = 4.3 m³
V_C = (1/7) × 15 = 2.14 m³

Concept:
The following is parameters and properties of cement:
1. Bulk density of cement = 1440 kg/m³
2. Specific gravity of cement = 3.15
3. Weight of one bag of cement = 50 kg
4. Volume of cement bag = 50/1440 = 0.035 m3
5. Number of cement bags in 1 m³ = 30 approx.
6. Volume of dry mortar is 30% more than the volume of wet mortar.
∴ The volume of dry mortar = 1.3 × volume of wet mortar
Calculation:
1 m³ of wet cement mortar will correspond to 1.25 m³ of dry mortar
Sum of proportions = 1 + 5 = 6
Cement = 1.3/6 = 0.216m³
1 m³ of cement = 1440 kg
So, 0.216 m³ to cement = 312 kg
Sand = (5 x 1.3)/6 = 1.08m³

The carpet area of residential building may be 50 % to 65 % of the plinth area of building with a target of 65 %.
Concept:
Carpet area of building is the useful area or liveable area or lettable area. This is the total floor area minus the circulation area, verandahs, corridors, passages, staircase, lifts, entrance hall, etc. and minus other non-usable areas as sanitary accommodations (bath and W.Cs.), air conditioning room etc.
For office building carpet area is the useable area and for residential building carpet area is the liveable area and should exclude the kitchen, pantry, stores, and similar other room which are not used for living purposes.
The carpet area of a building for any storey shall be the floor area excluding the following:
(a) Sanitary accommodation, (b) verandahs, (c) corridors and passages, (d) kitchen and pantries, (e) stores in domestic buildings, (f) entrance hall and porches, (g) stair cases and mumties, (h) shafts for lifts, (i) barsaties, (j) garages, (k) canteens, (l) air conditioning ducts and air conditioning plant room.
The carpet area of an office building may be 60 % to 75 % of plinth area of the building with a target of 75 %.
The planners should aim to achieve a target to 75 % of the plinth area. The carpet area of residential building may be 50 % to 65 % of the plinth area of building with a target of 65 %.

Plinth area: 

• It is the covered built-up area measured at the floor level of any storey or at the floor level of the basement.
• The plinth area is also called a built-up area and is the entire area occupied by the building including internal and external walls.
• It is generally 10-20% more than the carpet area.

In the Plinth area Estimate, Open areas, courtyard, and balconies should not be included in the plinth area valuation. This method is also known as an approximate estimate.

Cube rate estimate:

• This type of estimate is done by multiplying the volume of the building by the unit cubic rate achieved from the previously (also recent) estimate.
• This type of estimate is a little bit more accurate than the above-mentioned methods and mostly suitable for multi-storied buildings.

Unit rate estimate:
Uses predetermined output rates for labor and plant, in conjunction with a price per unit for materials, to calculate a rate per unit for some measured item of work, and this unit rate is then set against a total measured quantity.