Spread footings foundation and Grillage Foundation

Spread footings foundation :

This type of foundation ids simplest and commonly used in ordinary buildings. The base area of the foundation is increased by means of offsets to such an area which is sufficient to distribute the loads coming over it to bring the intensity of load within the safe bearing capacity of the soil. Wall footings, inverted arch footing, column footing, grillage, and raft are examples of spread footing.

Grillage Foundation :

This type of foundation consists of steel or wooden joists arranged in a stepped manner. It distributes the load over a larger horizontal area. A trench 90 cm to 150 cm deep is excavated and leveled. Then a layer of 23 cm to 30 cm of cement concrete is laid and compacted. Over this concrete, steel I-beams are laid and placed at a distance of 45 to 90 cm center to center. Length of these I-section is equal to the width of the foundation. Spaces between these I-beams is filled with cement concrete. Over this, the second layer of I-beams is placed at a right angle to the first layer. Again, the internal space is filled with cement concrete. The wall is then construction over this grillage bed.