What is Grillage Foundation, Definition, Construction, Uses

A type of foundation often used at the base of a column. It consists of one, two or more tiers of steel beams superimposed on a layer of concrete, adjacent tiers being placed at right angles to each other, while all tiers are encased in concrete. Grillage foundation is the most economical foundation in case of transferring heavy loads from columns to soil of low bearing capacity.

Grillage Foundation

Definition and Uses of Grillage Foundation

Grillage foundations consist of a number of layers of beams usually laid at right angles to each other and used to disperse heavy point loads from the superstructure to an acceptable ground bearing pressure.

The grillage beam can be in any material, the most usual being either steel, precast concrete or timber. In some permanent situations, however, where unusual circumstances exist, such as an abundance of durable timber or the possible re-use of existing rolled steel sections, the grillage can prove both successful and economic. In permanent conditions durability becomes an important design factor and protection and/or the selection of suitable materials is a major part of the design.

Design of Grillage Foundaiton 

The design of the grillage is carried out by calculating the loads and moments applied from the superstructure and determining the required base area using a suitable allowable ground bearing pressure for the condition involved.

From this area, the number and size of each grillage layer can be decided. The layers are then designed to cantilever from the edge of the layer above, which determines the beam sizes required to resist the applied bending moments and shear forces.


If the grillage is encased in concrete and the sequence and method of construction and loading is compatible with the design requirements, the composite action of the beam and concrete can be exploited.

Types of Grillage Foundation 

Mostly there are two types of grillage foundation based on type of material used;
a) Steel grillage foundation
b) Timber grillage foundation
Mostly out of these two types the decision is made on the basis of availability of material and overall cost is the deciding factor.