Estimate of Building Work – Long Wall Short Wall Method, Centre Line Method

Estimate of Building Work

It is essential to know the probable construction cost beforehand, called the estimated cost for building construction. 

If this cost is higher than the funds available, Work is reduced, or changes are made in the specifications to reduce the cost. By it, you can know the importance of estimate for civil engineers.

For making an estimate, the quantities of different work items are determined with the simple mensuration method, and these quantities help in the cost calculation.

The process of estimation is easy, not rocket science, but you must know drawing.

If you can read or understand the drawing, you may find the dimension length, width, height.   Essentially the calculation made of length x width x height/depth or length × height/depth.

You have to take the dimensions (length, width, height, or depth) from drawings(plan elevation and section).

Imagine the building and picture in mind to take the dimension correctly from the drawing study.

There is no fixed rule to determine the dimension from the drawing, but you must have to take measurements accurately.

Special attention is needed at corners, wall junction and wall meeting points.

Usually, foundations are symmetrical, for which the following methods may estimate quantities of different work items such as earthwork in excavation, foundation concrete, foundation brickwork, plinth and brickwork in the superstructure.

Also, Read - What is Plinth Area? - Calculation, Plinth Area Estimate

Method of Building Estimate

  1. Long Wall Short Wall Method
  2. Centre Line Method

Long Wall Short Wall method

The long wall short wall method is the simple method to estimate the quantity of different work items.

You have to determine the external length of the long walls out to out, usually running in a longitudinal direction.

The internal length of short or cross, or partition walls generally runs in the transverse direction. By multiplying this length with the width and height of the wall, you can calculate the quantities.

With the help of these walls length, you can calculate the different work items such as excavation in the foundation, foundation concrete and masonry wall.

But remember, you need to take care while noting the difference in dimensions at different height because of height offset or footing.

You have to imagine the drawing at different heights for convenience, such as foundation trench, foundation concrete, etc. and separately deal with each part.

The simple way to use this method separately consider the long walls and short walls and calculate the centre to centre distance of each wall from the drawing.

For the symmetrical footing on either side, the centerline remains the same for the superstructure and the foundation and plinth.

Also, Read - Building Estimate - Importance - Estimate of Building In Excel

Estimate of Building Work By Long Wall Short Wall Method

Out to out length of long wall = Centre to Centre length + Half-width of one side + Half-width of another side

= Centre to Centre length + One Width

In to in length of short Wall = Centre to Centre length – One Width

Usually, long wall length decreases from Erath work in excavation to brickwork and the short wall-length increase

Long Wall Short Wall Method
Long Wall Short Wall Method

From the above image

Centre to Centre Length of Long Wall = Inner Length + Half-width of one side + Half-width of another side

= 6 + 0.15 +0.15

= 6.30 meter

Centre to Centre Length of Short Wall = Inner Length + Half-width of one side + Half-width of another side

= 5 + 0.15 + 0.15

= 5.30 meter

NoItem DescriptionNo.Length
(meter)
Width
(meter)
Height
(meter)
Quantity
(Cum)
Remark
1.Earthwork in Excavation
Long Wall27.20 0.900.9011.664mLength = 6.30+0.90 = 7.20m
Short Wall24.400.900.907.128Length = 5.30-0.90 = 4.40m
2.Foundation Concrete
Long Wall27.200.900.303.89Length is same as above
Short Wall24.400.900.302.376Length is same as above
3.Foundation Brickwork
Long Wall
First Footing26.900.600.302.484Length = 6.30+0.60=6.90m
Second Footing26.800.500.302.04Length = 6.30+0.50=6.80m
Plinth26.700.400.603.216Length = 6.30+0.40=6.70m
Short Wall
First Footing24.700.600.301.69Length = 5.30 – 0.60=4.70m
Second Footing24.800.500.301.44Length = 5.30 – 0.50=4.80m
Plinth24.900.400.602.352Length = 5.30 – 0.40=4.90m
4.Superstructure Brickwork
Long Wall26.600.303.2012.672Length = 6.30 + 0.30 = 6.60 m
Short Wall25.300.303.2010.176Length = 5.30 – 0.30 = 5 m
Also, Read - House Construction Cost Calculator Excel Sheet

Centre Line Method

Centerline is another method for estimating building work. In this method, as the name indicates, the centre line length of walls, long and short, has to calculate.

You have to calculate the walls’ total centre line length of the same type, long and short, using similar foundations and footings. Now multiply this centerline length with width and height to calculate the quantities of the various work item.

The wall length will be the same for different work items such as excavation in the foundation, foundation concrete, footings and superstructure (with a slight variation in cross walls or the number of junctions). 

It is a fast method of estimation but needed special attention and consideration at junctions.

This method is suitable for circular, hexagonal, octagonal, etc., shape buildings with no inner or cross walls.

The buildings with inner or partition wall require special consideration to calculate the exact quantity for each cross or partition wall junction with main walls.

Estimate of Building Work By Centre Line Method

By multiplying the total centre line length with width and depth or height, we can calculate the quantities of different work items.

But when we do this, we take the certain part double and leave an equal part, but it doesn’t affect the quantity.

For instance, the excavation quantity = (AB x 0.90 x 0.90 + BC x 0.90 x 0.90 + CD x 0.90 x 0.90 + DA x 0.90 x 0.90).

Here you can notice that the parts K, L, M and N marked with double hatch line come twice, while the segment P, Q, R and S left blank don’t come at all since these parts are of equal dimension. Hence we get the correct quantity.

Also, Read - How to Calculate Cement, Sand and Aggregate In Concrete?
Estimate of Building Work - Long Wall Short Wall Method, Centre Line Method
Centre Line Method

From the above Image

Total Centre Length of Wall = AB + BC + CD +DA

= 6.30 + 5.30 + 6.30 + 5.30 = 23.2 m

No.Item DescriptionNo.Length
(meter)
Width
(meter)
Height
(meter)
Quantity
(Cum)
Remark
1.Earthwork in Excavation123.20.900.9018.79Total Center length = 23.2
2.Foundation Concrete123.20.900.306.26
3.Foundation Brickwork
First footing123.20.600.304.176
Second Footing123.20.500.303.48
Plinth Wall123.20.400.605.568
4.Superstructure Brickwork123.20.300.302.088Deduction for opening have to done.

I hope now you have enough knowledge and the Long Wall Short Wall method and Centre Line method. Please share it.

Thanks!

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