Foundations are usually used for multistory buildings or buildings located on soft soil are the foundation footprint / foundation of reinforced concrete slab that is placed directly below the column or beam with a depth to the ground hard. Making this foundation can be combined with a foundation stone or concrete Sloof directly with a specific dimension for the benefit of the wall installation. This foundation can also be prepared for the buildings in the narrow ground that will be the development of building upward. Types of materials for the manufacture of concrete slab foundation is stone broke (split 2 / 3), concrete sand, cement PC (gray cement), steel, and lumber for form work or mold.
a. Calculating the volume of foundation
How to calculate the volume of concrete foundation of a local concrete slab are as follows.

Volume foundation = Volume I + Volume II
Volume I = Area of cross section x Height

Volume II = (a + b/2) x b

Description:

a. = Width of the top of the foundation
b. = Height of foundation
c. = Width of the foundation brought

b. Calculate the material needs
When the sand and the split of good quality, minimum quality of concrete can reach the K175. K is the symbol of the strength characteristics of concrete, for example, K125, K150, K175, K225, and so on. The need for material per m3 of reinforced concrete slab foundation with cement mortar 1: 2 sand: 3 split is

1. Crushed stone / split 2 / 3 as much as 0.83 m3,

2. 0.54 m3 of concrete sand,

3. PC as much as 8.5 bags of cement

After the volume of concrete foundation to be built is calculated, the needs of each component multiplied by a factor of building materials in the above so that the volume needs to be obtained of each material. For example, the foundation will be made is 100 m3 and so we need
1. Crushed stone / split 2 / 3 as many as 83 m3 (0.83 m3 x 100)

2. Concrete sand as much as 54 m3 (0.54 m3 x 100)

3. PC as much as 850 bags of cement (8.5 bags x 100)