Expert estimators are able to work out the quantities of concrete, steel, brickwork, plaster and finishing material based on the total built-up area of a residential building without even looking at the building plans.
So here’s a rough guide on working out the quantities for a residential building of approx. 1 lakh square foot built-up area.
Concrete- Approx 4500 cum of concrete would be required for the structural frame of the building. The thumrule to follow is 0.045 cum of concrete per square foot of built-up area. This quantity would increase slightly for a building having basements as extra concrete would go in the raft, retaining walls and to the ramps to the basement.
Rebar- Approx 540 tons of rebar would be required. The thumbrule to follow is 120 kg of rebar per cum of concrete. Highrise buildings require more steel in the colums and the amount of steel per cum of concrete would increase with the height of the building.
Brickwork – Approx 1.3 lakh sq feet of wall would be present in the building with 1 lakh square feet area. However, the total area of the walls would depend a lot on the size of rooms.
Plastering and Paint Area – is approximately 3 times of the brickwork area . Note that this also includes ceiling and staircase plastering.
These numbers only apply to large residential towers and not to small housed and bungalows. Please apply these numbers with caution as they may vary for your particular project.
Suppose on a project, one had to complete 1000 cum of concrete in a month, how should one plan the manpower for that.
Of course productivity depends on the type of structure, but I am speaking of a general approach and not specific to a certain type of structure.
For a general concrete structure we can assume 0.1 ton of rebar per cum of concrete on the average.
So 1000 cum of concrete works out to 100 ton of rebar.
Based on site observations a bar bender with 2 helpers does approx. 0.4 ton of bar bending, cutting and fit-up in a day.
So 1 gang of bar benders ( 1 main bar bender and 2 helpers) would do approx. 10 tons of reinforcement work in a month ( assuming 25 working days)
Hence to do 100 tons of rebar in a month 10 gangs would be required.
For shuttering, we can assume that 4sqm of shuttering would be required per cum of concrete.
Hence for 1000 cum of concrete, 4000 Sqm of shuttering would be required.
One carpenter with 2 helpers do approx. fit up of 4.5 Sqm of shuttering in a day.
So 1 gang of carpenters would do approx. 112.5 Sqm of shuttering in a month
Say 100 sqm in a month
So in order to compete 4000 Sqm of shuttering in a month, 40 gangs of carpenters are required.