AREA METHOD OF ESTIMATING BLOCKS
The area method of estimating is one of the methods adopted for easy calculation of the number of blocks that will be required to complete a particular building project. This article seeks to help those in the building industry who have difficulties in carrying out this task for their prospect client.
After deciding to carry out a building project, the first most asked question from a client or who would be house owner is always how many blocks do I need to get my building completed? Therefore, the estimation of the number of blocks for a building is a very important aspect of a building project.
Below is an illustrative example of how to carry out the calculation of the number of blocks using the area method of estimating blocks.
Note: this calculation is not peculiar to one particular size of block says 9”, 6” or 5” since all these blocks have equal length of 450mm being it solid or hollow.
ILLUSTRATIVE EXAMPLE USING THE AREA METHOD OF ESTIMATING BLOCKS
Estimate the number of blocks needed to complete a building whose total perimeters is 100,250 mm = 100.25m with the following features.
DOORS AND THEIR TYPES
(D1) = 1 piece (Dimension = 2100 × 1200) for main lodge or living room
(D2) = 6 pieces (Dimension = 2100 × 900) for sleeping rooms and kitchen
(D3) = 4 pieces (Dimension = 2100 × 700) for bathroom and toilet
WINDOWS AND THEIR TYPES
Window Type 1 (W1) = 12 pieces (Dimension = 1200 × 1200)
Window Type 2 (W2) = 4 pieces (Dimension = 600 × 600)
Veranda opening 1 (Dimension =6000mm x 2325mm)
Balcony opening 1 (Dimension = 2100mm x 2325mm)
Dining opening 1(Dimension = 2400mm x 2325mm)
Lintel casting (assuming the building was chain at the lintel level) (Dimension = 100256mm x 225mm)
Foundation depth to DPC = 900mm (not fixed depending on the area).
Building height from DPC to overhead (roofing level) = 3000mm
Every building consists of three main phases. They are:
- Foundation to DPC
- DPC to lintel level, and
- Lintel level to overhead level (roofing level)
Estimation of the number of blocks using the area method.
The simplest approach to estimate the number of blocks required for a building is using the area method of a meter square of wall.
The planar dimensions of a standard blocks mostly use in Nigeria are as follow
The nine inches block (9”) measured 450mm × 225mm x 225mm (always hollow)
Six inches block (6”) measured 450mm x 150mm x 225mm (it can be solid or hollow)
The five inches (5”) measured 450mm x 125mm x 225mm (always solid)
From the dimensions of the block above, the only thing that differentiates them is their thickness. The length and breadth which is considered the height of the block are the same. Therefore, the calculation of the number of blocks using the area method is not limited to a particular size of the block since the planar face (length and breadth) of the three sizes of blocks are the same. This means that the area of any of the block is = (450 x225) mm = (0.45 x 0.225) m = 0.10125 m2
Since we are going by area method, it, therefore, means that we will calculate the number of blocks per meter square of the building walls. This, therefore, follows that: one meter square of the building wall will take 1/0.10125 = 9.876
This means that one meter square of wall will take approximately 10 blocks.
CALCULATIONS – AREA METHOD OF ESTIMATING BLOCKS
Total height of building from foundation to overhead level = 3000 + 900 = 3900mm = 3.9m
Total perimeters of building = 100250mm = 100.25m
Area of block wall of the building = 100.25 x 3.9 = 390.975m2
(D1) = (2100 × 1200) = 2.1 x 1.2 x 1 pieces = 2.52m2
(D2) = (2100 × 900) = 2.1 x 0.9 x 6 pieces = 11.34m2
(D3) = (2100 × 700) = 2.1 x 0.7 x 4 pieces = 5.88 m2
WINDOWS AND THEIR TYPES
(W1) = (1200 x 1200) = 1.2 x 1.2 x 12 pieces = 17.28m2
(W2) = (600 x 600) = 0.6 x 0.6 x 4 pieces = 1.44 m2
Veranda opening 1 (6000 x 2325) =6 x 2.325 =13.95 m2
Balcony opening 1 (2100 x 2325) = 2.1 x 2.325 = 4.8825 m2
Dining opening 1(2400 x 2325) = 2.4 x 2.325 = 5.58 m2
Lintel (concrete) (100256 x 225) = 100.256 x 0.225 =22.5576 m2
Total area of openings = 2.52+11.34+5.88+17.28+1.44+13.95+4.8825+5.58+22.5576 = 85.4301m2
Therefore, area to be cover with block = 390.975 – 85.4301 = 305.5449m2
The number of blocks needed will be = 305.5449/0.10125 = 3017. 727 pieces of blocks.
The total number of blocks required to construct the building whose total perimeter is 100250mm with the given features will approximately = 3018 pieces (excluding all forms of wastage)