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The Influence of Design on Building Cost - Introduction
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OBJECTIVE:

To introduce members of the public who are involved with building projects to certain of the cost implications of design variables so as to enable them to evaluate and implement a rudimentary cost benefit approach to future projects.

BACKGROUND TO THE PROBLEM:

Let us look at a practical problem which has cropped up many times in the past and, I am sure, you have come across as well.

Buildings A and B are designed to meet the same needs i.e. both are office blocks or hotels, shops, houses, etc., yet when comparing the costs per m² of floor area, we find that Building A costs say R10,000/m² while Building B only costs R7,500/m². Further analysis shows that they have the same external and internal finishes with similar roof and floor constructions. In fact there seems no apparent reason why the rates should not be exactly the same.

This exercise is meant as a guide to enable you to explain such discrepancies in a more meaningful way.

THE SQUARE METRE RATE:

This method of expressing the cost of buildings is quite convenient and therefore widely used in cost comparisons and rudimentary cost planning. It is calculated by dividing the net cost of the building (excluding site works, cost of land, etc.) by the gross square metres of the building or Gross Floor Area (GFA). Typically GFA can be defined as the total floor area inside the building envelope, including the external walls, and excluding the roof.

Considerable care has however, to be taken in using costs expressed in this way to make allowance for widely differing conditions on different projects.

Let us examine some design variables which can influence our square metre rate adversely.

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