Preliminary Estimate | Numericals of Preliminary Estimate

  1. Introduction  

The preliminary estimate is an estimate to seek out an approximate cost quickly.

It is also known as a rough estimate made in any project’s early stage of design work.

A preliminary estimate is prepared based on the practical experience of carrying out similar works in the past and their rates.

This estimate is enclosed with a brief project report, including its necessity, utility, and layout plan.

The preliminary estimate is also prepared for renovation works and demolition works.

It can also be carried out in the absence of drawings and specifications.

Generally, the preliminary estimate is provided by contractors and builders to the owner.

More details provided by the owner result in more accuracy of the estimate.

The preliminary estimate is prepared for buildings, roads, irrigation channels, etc.

For Roads: Rate per kilometer is provided based on the pavement’s thickness, materials, and width.

For Buildings: Rate per square foot or square meter is provided based on the type of construction and materials used.

For Irrigation Channels: The rate per km is based on the channel type.

  1. Steps in Determining Preliminary Estimate Cost in Buildings  

a. Determine the plinth area of the building. For multi-storeyed buildings, determine the plinth area of each story.

b. Calculate the building cost by multiplying the plinth area and rate per square meter.

Building Cost = Plinth Area *  Rate per square meter

c. Determine the Cost of services that are based on building cost.

For e.g., Cost of electricity is 10 % of the building cost, and the building cost is 20,000 $ then;

Cost of electricity = 0.1 * 200 = 2,000 $

d. Determine Overall Cost by adding building cost and services based on building costs.

Overall cost = Building Cost + Services based on building cost 

, e. Determine the Cost of services based on the overall Cost.

E.g., the Cost of sanitation and water supply is 5 % of the overall Cost, which is 50,000$ then.

Cost of sanitation = 0.05 * 50,000 = 2500 $

f. Always take the Cost of contingencies and supervision between 7 to 12 % of the overall Cost.

g. Calculate total Cost by adding overall Cost, services based on overall Cost, and Cost of contingencies and supervision.

Total Cost = Overall cost + Cost of services based on overall Cost + Cost of contingencies and supervision

  3. Steps in Determining Preliminary Estimate Cost in Roads  

a. Determine the road length.

b. Select the rate per km based on the road’s thickness, materials, and width.

c. Calculate the overall Cost by multiplying the road length and rate per km.

Overall cost = Length of road in km * Rate per km

d. Calculate the Cost of supervision and other technical services (like the Cost of tests performed ).  Generally, this takes 10 to 30 % of the overall Cost.

e. Determine total Cost by adding overall Cost and Cost of supervision and technical services.

Total Cost = Overall cost + Cost of supervision and technical services

Note: Preliminary estimate of irrigation channel is same as an estimate of road. 

  4. Advantages of Preliminary Estimate  

a. To get surface detail about the approximate Cost of construction.

b. It helps the client choose the best contractor in terms of economy.

  5. Preliminary Estimate Includes  

a. Date of Estimate.

b. Approximate Cost of construction.

c. Cost of different categories like water supply and sanitation, electricity, contingencies, etc.

d. Some detail (like name, signature, etc.)  of the preparing person.

  6. Numericals of Preliminary Estimate – Buildings  

1. Prepare a preliminary estimate of a building with a plinth area of 1600 square meters.

Given that

i. Plinth area rate= $ 200 per m²

ii. Extra for architectural work=  1 ½ % of building cost

iii. For electrical installation= 10% of building cost

iv. For water supply and sanitary installation= 5% of the overall Cost

Solution,

i.
1m² rate cost = $ 200

1600m² rate cost = 200×1600 = $ 320,000

∴ Building cost= $ 320,000

ii.

Extra for architectural work=  1 ½ % of building cost

= 0.015 * 320000

=  4,800 $

iii.
For electrical installation,

= 10 % of 320000

= 0.1 * 320000

= 32,000 $

Overall cost = 320000 + 4800 + 32000

= 356,800 $

iv.

For water supply and sanitary installation= 5% of the overall Cost

= 0.05 * 356800

= 17,840 $

Again,

Note: most 10 % of the overall Cost is assumed for supervision & contingencies 

Contingencies and supervision charge = 10% of 356800

= 35,680 $

Total cost = 356,800 $ + 17,840 $ + 35,680 $
= 410,320 $

2. Prepare a preliminary estimate of a multistoried office building having a carpet area of 1600 m². The circulation area is 30% of the building, and the wall area occupies 10%. The rate is $ 70 per m².

The electricity and sanitary installation cost is 10% of the building cost. External services are taken as 2% of the building cost. Contingencies and supervision charge 4% and 5% of overall Cost, respectively.

Solution,

Let x be the plinth area.

Plinth area = carpet area + circulation area + wall area

x = 1600 + 30% of x + 10% of x

x = 1600 + 0.4x

x – 0.4x = 1600

x = 2666.6 m²

Building cost = 70 × 2666.6

=  $ 186,662

Cost of electricity and sanitary installation,

= 10% of 186662

= 18,666.2$

External services = 2% of building cost

= 0.02* 186662

= 3733.24 $

Overall cost= 186662 + 18666.2 + 3733.24

= 209061.44 $

Cost of contingencies and supervision =  9% of 209061.44

=  18815.53 $

Total = 209061.44 + 18815.53

= 227876.97 $

  7. Numericals of Preliminary Estimate – Roads  

1. Find the preliminary estimate of the road length of 10 km. The width of the road is 8 m, and the thickness is 0.2 m. The rate per km for the given road is 8,000$.

Solution,

Overall cost = Length of road in km * Cost per km

= 10 * 8000

= 80,000 $

Note: Take 10 to 30 % of the overall Cost for supervision and technical services

Cost of supervision & technical services  = 20 % of the overall cost

= 0.2 * 80000

= 16,000 $

Total Cost = Overall cost + Cost of supervision and technical services

= 80000 + 16000

= 96,000 $