Dear Reader ,
In my experience , the subject of estimation is quite boring to the students as well as field people.
In that context , we are going through a series of articles devoted to the arithmetic involved in construction.
We have already discussed the estimation of materials in concrete
( Read post : Vow..what a concrete )
Now we shall travel in the masonry today.
Just keep your patience when you read.
If you get bored , just Stop and take a break.
Take a scrap pad and a calculator and do some jugglery yourselves.
That’s how you shall keep aligned .
Re-continue and reflect as many times as you feel.
There is no hurry.
Happy Calculating !
( Read : Throw the stone..carefully )
We shall be able to find out the :
Number of bricks needed for the masonry work and also the mortar needed for the job.
In other words ,for a given masonry wall we shall be able to compute:
2.No of cement bags
This shall help us in:
1.Budgeting for materials
2.Ordering the material
The brick wall which we need to build is 5 m long, 4 m high and it is 200 mm thick.
It is to be jointed in Cement mortar 1:6.
The bricks of size 200 mm x100 mm x 70 mm have been approved.
1.Calculate the volume of one brick :
0.2m x 0.10m x 0.07m = 0.0014 CuM.
2.Find number of bricks per CuM:
= 1/0.0014 = 714 nos.
3. Now,assume that there is a mortar joint of 10 mm thickness between the bricks.
So, increase each dimension of brick by 10 mm.
Thus,the volume of each brick with mortar shall be :
0.21 x 0.110 x 0.08 =0.001848 CuM.
= 1/0.0011848 = 541 nos.
5.Thus, number of bricks have reduced from 714 to 541 due to the presence of mortar.
6.Therefore, 714 – 541 = 173 Bricks represent the volume of cement mortar.
We shall need 541 bricks and 0.24 CuM of cement mortar for 1 CuM of brick work.
8.Now we also need to find out how many cement bags and how much quantity of sand is needed
for 0.24 CuM of mortar .
The mix is CM 1:6.
We shall use dry mix method.
Sand: [0.2171] x 6 = 1.302 CuM.
Cement: 6.25 Bags
Sand: 1.302 CuM.
Hence for 0.24 CuM of mortar , we shall need :
Cement: 6.25 Bags x 0.24 =1.5 bags
Sand: 1.302 CuM. x 0.24= 0.3125 CuM.
Consumption of materials for 1 CuM of Brickwork :
Cement: 1.5 bags
Sand: 0.3125 CuM.
Bricks: 541 Bricks
10.Now we are at the final lap:
Volume of brick wall:
5 x 4x 0.2 = 4 CuM
Cement: 1.5 bags x 4 = 6 bags
Sand: 0.3125 CuM. x 4 = 1.25 CuM.
Bricks: 541 Bricks x 4 = 2164 Bricks
If the unit rates are known we can also find out total cost of the materials.
11.Assume that :
Bricks : INR 4200 per 1000. [ INR 4.2 per no ]
Sand : INR 4500 per Brass or 100 Cft.
[ INR 45 per cft or 45 x 35.29 = INR 1588 per cuM.]
Cement : INR 300 per bag of 50 Kg.
The material cost shall be as follows :
Cement: 6 bags@ 300 = 1800
Sand: 1.25 CuM.@ 1588 = 1985
Bricks: 2164 Bricks@ 4.2 = 9088
Total cost :1800 + 1985 + 9088
= INR 12,873
12. Now we can find out the materials cost per CuM of brick work :
12,873 /4 = INR 3218.25 per CuM of brick work
or 3218.25/35.29 = INR 91.19 per Cubic feet of brick work
Author’s note :
Dear Reader ,
Hope you have understood the basics.
1.Remember , you don’t have to do all this calculation every .
Just memorize the unit cost i.e INR 3218.25 per CuM or INR 91.19 per Cubic feet of brick work .
As long as the material rates are the same, the cost shall be the same.
2. For those comfortable with spread sheets , once do this calculation in the spread sheet with proper formulae. Later , when any of the variable changes ,the moment you revise that figure, the entire computations shall be automatically revised.
Its really a fun.
Happy journey on the path of estimations.