Design variables may influence the building cost

 

i)  Plan shape

If the building has a simple shape, the unit cost will be lower. This is because the simple shape has lower floor area than the irregular shape due to their large floor area. In addition, irregular shape tend to have complicated calculation and has more perimeter on the floor area. Next, the building will be more economical if it has lower wall which mean floor area ratio. However, it is not design that is practical and suitable for building function that is limited. The cost of a building will differ with changing the shape of the plan shape even the other factors remain unchanged. 

In addition, if the building are built together, it will save the cost where it combine the party walls. The party wall is shared together by two unites of building. The changes in cost can be determined or can be known if the building is combine together.

For example, as you can see, building A has L-shape and building B has irregular shape. Hence, assumed the ground floor area for both building has the same value which is 525 meter square. Then, assumed there are 2 storey = 500 x 2 = 1000 meter square. As for wall thickness, for building A is 50m and building B is 80m. For wall height for building is 6m. 

To calculate:

Enclosing area: (length x height of wall)

Building A = 50m x 6m = 300 meter square

Building B = 80m x 6m = 480 meter square

To calculate wall or floor area ratio:

Building A = 300 / 1000 = 0.3

Building B = 480 / 1000 = 0.48 

Therefore, building A is more economical. It is not economical for building B as the enclosing wall has greater or large area. 

ii)  Size

The bigger the size of building, the unit cost of per meter square of the building will be reduce. Reduction in cost and structure size due to reduction in dead load. 

For example:

To calculate floor area, building A = 20m x 20m = 400 meter square and building B = 40m x 20m = 800 meter square. 

For length of enclosing wall builing A is 20 m + 20m + 20m + 20m = 80m

Building B = 40m + 20m + 40m + 20m = 120m

For length of wall per meter square of floor area:

Building A = (80 / 400) = 0.2m , (then times with 1000) = 200mm

Building B = (120 / 800) = 0.15m = 150mm

When constructing  a big building, the total cost of the building is more than the small building. When there is an increasing size, it means that there are increase in term of quality of construction, material, high usage of electricity and use a bigger machinery plant. However, cost does not rise in proportion with increase size. Cost such as transportation, construction and demolish, a store construction, temporary access road do not increase the project size which mean the cost remain same. 

It is more economical to construct a bigger building than the small building which has the same floor area with big building due to cost such as external wall and related works. 

Name: Nur Aida Sabrina Azman

Student id: 2019324599

Class: AP2294B