GRILLAGE FOUNDATION AND TYPES GRILLAGE FOUNDATION

May 30, 2023

Grillage foundation is a type of foundation that consists of more than one extra layer of beams which are usually steel placed on a layer of concrete to distribute and transfers the structural load on a big area of soil below the foundation.

These types of foundations are used for heavily loaded columns. Grillage foundation has various layers of the beam which are cover into concrete and each arranged 90 degrees to the other. This foundation type is mostly used for scaffolds, heavily loaded structures, and column construction.

Following are the Grillage Footings types,

The steel grillage foundation consists of steel beams placed in single or double tiers and enclosed concrete.

The grillage beams of each tier are held in position by 25 mm-diameter pipe separators and 20 mm spacer bars. The beams are spaced appropriately to allow the placement and compacting of concrete between them.

It is recommended that a minimum clearance of 8 cm be maintained between the two beams. In any event, the distance between the beams’ flanges should not exceed 1.5 to 2 times the flange width, with a maximum of 30 cm.

A minimum cover of 10 cm is maintained on the outside edges of the external beams and above the upper flange of the top tier to protect the beams from corrosion. The concrete cover under the lower beam should not be less than 15 cm.

Timber grillage foundation is used where the soil is soft and is permanently water-logged. A suitably designed timber grillage foundation can economically support the building walls.

By restricting the soil weight to 5.5 tonne/sq.mt, a wood platform replaces the concrete block that is generally given below the wall footing in this construction style.

The wood platform comprises boards that are typically 8 to 10 cm thick and are stacked in two layers, one longitudinal and the other across the wall, reaching 45 to 60 cm beyond the footing foundation on each side.

The boards are 5 cm to 10 cm thick at the bottom levels, depending on the loads and site conditions. Rectangular portions of timber spaced at no more than 38 cm center to center, with a depth of 0.75 times the width, divide the two layers of planks.

Following are the Advantages of Grillage Beams,

Disadvantages of Grillage Foundation are listed below: