Plans are important because they would show completely what the client’s needs are.
In order to answer this question, i am going to upload a plan since I’ll be estimating based on the dimensions found on the building Plan
I am going to use the floor plan of a 2 bedroom Bungalow shown above as a case study, so i would like you to pay more than usual attention as i gradually unfold this for your understanding…
Point A: There are 3 different types of block in Nigeria, these are
i. 5″ Sancrete Block or 125mm block
ii. 6″ Sandcrete Block or 150mm Block
iii. 9″ Sandcrete Blocks or 225mm Block
iv. 6″ Sandcrete Solid Blocks or 150mm block
Of all these, 5″ and 6″ are the most common because they are usually cheap and commonly used for small projects
Point B: The length of a sandcrete block is 18 inches or 450mm or 0.45m
Point C: Depending on the nature of the site, the blocks laid from the foundation level to the DPC (The level at which you Damp Proof or apply Over-site concrete) is usually 4 coaches or levels unless its a swampy site where the you may get to 5-7 coaches before the DPC
Also, from DPC to the base of the window, you’re required to have 4 coaches, from the base of the window up to the top of the window, you have another 5 coaches. Now from the top of the window to the base of the roof is another 3 coaches. We are going to neglect the lintel or concrete on top of the window
Remember we are going to be using the 6 inches block or 150mm sandcrete blocks
all through the building.
Now the first thing to do is to add up all the external and internal dimensions from the architectural plan above.
we have successfully marked the plan into 4 different sides: A, B, C, D
So from the sides, we Calculate the Building girth
How to Calculate the External girths of a building
Add up all the external dimensions
A 9000mm +
B 7925mm +
C 11500mm +
D 11500mm = 39,925mm
The total = 39925mm or 39.9m
How to Calculate the internal Girths Of A Building
Having Added the externals, lets also add the internal dimensions (The dimensions other than those outside the building)
We are going to follow A Systematic pattern here. we will first of all get the dimensions of all the vertical dimensions other than A – D
Now the vertical internal dimensions are:
2150mm = 18650mm or 18.65m
Now lets get the horizontal Dimensions as well and add up the totals
2000mm = 23850mm or 23.85m
Total Internal Girth = 23850mm or 23.85m
Remember total External Girth = 39.9m
Therefore, the total Girth (External + Internal) = 42500 + 39925 = 82425mm or 82.42m
Now, lets estimate the number of Blocks that would be able to enable us get to the DPC Level (Here, we will not remove doors since the digging covers everywhere including doors and windows)…
Since the length of one block =450mm, we are going to divide the total Girth which is 82425mm by 450mm
82425/450 = 183 block/coach (This means for every coach, we would need 183 blocks).
To get the total for all 4 coaches, we multiply by 4
So 183 x 4 = 732 blocks (Would be required to reach the DPC Level if: the site is located on a flat terrain that is not swampy)
Now Lets Determine the total number of blocks needed for the entire 3-bedroom flat
To do this, we need to know the number of block for each segment of the building
From Foundation to DPC = 4 Coaches
From DPC to window level = 4 Coaches
from Bottom of window to top of window = 5 Coaches
from Lintel to the base of the roof or Gable = 3 coaches.
We have a total of 16 Coaches In all
So We Multiply 183 x 16 = 2928 – 732 (used to dpc level above) = 2196 Blocks
We will now Deduct for Voids
What Are Voids In A Building?
Voids are open spaces like doors and windows
They are not usually covered with blocks thus the name.
Now lets Subtract windows and doors, lines where burglary would be used instead of blocks from 2196 blocks
Now for every 1500mm window, we understand from experience that a total of 22 blocks would be needed to fill the space so we remove this 22 blocks for all 1500mm window
How to Know the number of Blocks to remove for every 1500mm Window
1500/230 = 6.5
also, 1500/450 = 3.3
(6.5 x 3.3) = 22 Blocks
How many 1200 windows do we have in the building?
Counting, we have exactly 8 windows with the 1500mm dimension
so the number of blocks to be subtracted for windows = 8 x 22 = 176 blocks.
What is the Dimension for doors in a building?
The standard door for a bungalow is usually 900mm or 3 feet
How many Blocks do i deduct for a 900mm door?
You deduct a total of 18 blocks for every doo
How do i calculate the number of blocks deductable from a door?
The height of a door is usually 2100mm
divide this by 225 (2100/225 = 9) + width of the door divided by 450 (900/450 = 2) now 9 x 2 = 18 blocks for every 900mm door…
We also have a 1200mm Door
Now For a 1200mm door, lets see how to work out the number of blocks for a 1200mm door.
Door Width = 1200
Door Height = 2100
2100/230 = 9
1200/450 = 2.66
total = 9 x 2.6 = 24 Blocks
Now How many doors are there in a 3 bedroom flat?
we have a total of 7 doors, so we say 18 blocks x 7 doors = 126blocks
Now sum the number of blocks deductible (22+176+24+126)
Now remove 348 Blocks from 2196
2196 – 348 = 1848 blocks
Therefore, a total of 1848 + 732 = 2580 Blocks would be required for the job
I hope you found this useful in your practice as a site engineer
, Architect or an estimator.
Now i hope i have been able to answer the question “How to calculate the number of blocks required to build a 2 Bedroom flat” and i hope you will found this useful.