To (very) roughly estimate the cost of a building, Multiply the no. of floors by the approximate/average area of each floor. Multiply the product with an estimated 0.2m (usually 0.15-0.2m) for each floor slab thickness. That will give an estimate of the concrete to be used. (Note that most of the concrete is used in slabs and contribute to the high cost). The quantity of Concrete obtained is then multiplied by the rate price (currently around KES21,600.00 for class C25/20 concrete). The multiply the cost by a factor of 1.5 to compensate for steel, placing of concrete, formwork, walls (masonry/glass), columns etc.
Then multiply the product with a factor of 1.2 ( electro-mech works like lifts, lighting etc, Architectural works and Consultancy (U will need a physical planner, quantity Surveyor, Architect (the boss here), Civil and structural engineers and Electrical and Mechnaical Engineers. Nowadays, Landsscape architects are also needed)
EXAMPLE: Suppose we take Times Tower to be 32 floors 75mby 75m, THEN;
(32floors X 75m X 75m x 0.2m X KES21,600 X 1.5)X1.2 = KES1,399,680,000.00 = KES1.4B.
NOTE: THIS IS A VERY ROUGH ESTIMATE BUT CAN BE USED AS A PRE-FEASIBILITY STUDY ESTIMATE!
Receive with simplicity everything that happens to you.” ― Rashi