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CONVENTIONAL FOUNDATION

THE FOUNDATION

The Foundation is the section of structure below ground level up to the soil. It is in direct contact and transmits a load of superstructure to the soil. If some part of the foundation is above ground level, it is also covered or filled with earth. This portion of the structure is not intended to be visible or exposed to the air or light.

DEPTH

The depth of the foundation depends on several factors. This includes adequate bearing capacity, and amounts of shrinking or expanding, due to seasonal changes causing perceivable movement. Depth of frost penetration, nearby excavation, and the depth of groundwater. The practical minimum depth of the foundation should not be less than fifty centimeters. The recommended depth should range between one and one and a half meters.

FOOTING

The footing is a structure constructed in brickwork, masonry or concrete. This foundation would be placed under the base of a wall, or column, for distributing the load over a large area.

WIDTH OF FOUNDATIONS/FOOTING

The width of footings should be laid according to the structural design. This would be for light loaded buildings such as houses, schools, etc., having not more than two stories. The width of the foundation should not be less than seventy five centimeters for one brick wall, and not less than one meter for one and a half brick wall.

DIFFERENT PROCESSES IN FOUNDATION WORK

The processes executed in foundation work includes the excavation of earth in trenches for foundations, the laying out of cement and concrete, as well as footing for rafts or columns. In addition, anti termite treatment, laying brick work up to base level, damp proof course on walls, and refilling of earth around walls, along with refilling in the building portion up to the required height according to the base level.

PRECAUTIONS WHILE DESIGNING THE FOUNDATION

A foundation should be designed to transmit combined dead loads, imposed loads and wind loads affecting the ground. Loading intensity pressure affecting the soil should not exceed the safe bearing capacity. The foundation should have limited settlement upon the ground and be of a uniform nature, across the entire structure to avoid any damage. These characteristics should be studied for the initial construction work.

RATIO OF CEMENT CONCRETE AND MORTAR FOR FOUNDATION

The cement concrete ratio of 1:8:16 is generally used in the foundation of walls in construction. In case of column raft cement concrete 1:4:8 is the best recommended ratio for it in the foundation. For brick masonry cement mortar 1:4 to 1:6 is used as the loading condition. In case of column and raft footings up to base level cement concrete 1:2:4 or 1:1.5:3 are used.

SOIL HAVING SAFE BEARING CAPACITY

Dry, coarse, and well graded dense sand, have maximum shear resistance and maximum bearing capacity. In general submerged soil and clay have less bearing capacity.

PRECAUTIONS DURING EXCAVATION OF FOUNDATION WORK

The depth and width of the foundation should be established according to the structural design. For example, the depth of the foundation should not be less than 1 meter, if no design is available. The length, width and depth of the excavation should be checked with the help of the center line and designated level. The excavated material should be dumped at a distance of at least 1 meter from the edges of the foundation. The work shall be performed on dry soil. A water pump may be required for the removal of rainwater. The bottom layer of the foundation should be compacted and no soft areas available. Any soft or defective spots should be dug out and filled with concrete or a similar hard material.