Grillage Foundation: Types and Construction Details

When it comes to building a strong foundation, “grillage foundation” is a simple yet important concept. This introduction dives into the basics of grillage foundation, a method using a network of steel beams to distribute the weight of a structure. Whether you’re a homeowner or interested in construction, understanding grillage foundations can help grasp the essentials of supporting structures securely.

What Is A Grillage Foundation?

A grillage foundation is a type of foundation that consists of a series of interconnected steel beams and concrete footings. It is commonly used for heavy structures, such as bridges, towers, and large buildings, where the loads are too heavy for traditional foundation systems.

Grillage foundations are designed to distribute the load of the structure evenly across the soil, reducing the risk of settlement or differential settlement. This is accomplished by transferring the load to a larger area of soil through the use of steel beams and concrete footings.

Types of Grillage Foundation

There are two main types of grillage foundations:

  1. Steel Grillage Foundation.
  2. Timber grill foundation.

1. Steel Grillage Foundation

Steel Grillage Foundation
Steel Grillage Foundation

The Steel Grillage foundation is composed of beams and steel joints assembled in one or more layers, and its name reflects its primary function as it is made from steel beams known as as-rolled steel beams. A minimum coverage of 10cm is maintained on the external face of the outermost beams, which is higher than the highest flanges of the topmost tier, while the concrete depth should be at least 15cm.

During the leveling of the base and pouring of the concrete, it is essential to ensure proper compaction of the concrete and maintain a minimum spacing between the materials. The presence of steel in this type of foundation provides protection against groundwater that can potentially corrode the steel used in the foundation.

Once the concrete has gained sufficient strength, the second layer of steel beams is positioned in the same location as the pipe separators used previously. Concrete is again poured to encase the beam from all sides.

2. Timber Grillage Foundation

Timber Grillage Foundation is a cost-effective solution for supporting load-bearing walls in areas with waterlogged or permanently soft soil.

It can support low-loading buildings with a soil load capacity of up to 5.5 tonnes/ Instead of using a concrete block below the load-bearing wall, Timber Platforms are used to construct the foundation.

Timber Grillage Foundation
Timber Grillage Foundation

mm to support load-bearing walls in areas where soil is waterlogged or permanently soft. These platforms are placed in two layers, one extending longitudinally across the foundation and the other extending beyond the footing base by 45cm to 60 cm on both sides.

To ensure stability and support, the bottommost layers of planks are 50 mm to 100 mm thick, based on site conditions and loading on the walls.

The two layers of timber planks are separated by a rectangular timber section, with a spacing of no more than 380 mm. The depth of each section is approximately 0.75 times the width of the section.

Read More: 8 Foundation Construction Steps | House Foundation Construction Steps

Design Of Grillage Foundation

Grillage foundation design is a crucial aspect of constructing a building or structure that requires a strong and stable foundation.

A grillage foundation is a type of foundation made up of steel or timber beams and concrete, and it is typically used in areas where the soil is not stable enough to support a regular foundation.

The design process involves taking into account various factors such as the load requirements of the structure, the soil conditions, and the type and spacing of the beams to be used.

A structural engineer typically carries out the design process and determines the size, depth, and spacing of the beams required to provide sufficient support for the structure.

Once the design is finalized, the construction process involves preparing the site, excavating the area, and laying the foundation. The beams are then laid out and assembled, and concrete is poured around them to provide additional stability.

Proper grillage foundation design and construction are essential for ensuring the safety and stability of any building or structure.

Advantages of Grillage Foundation

The following are the Advantages of Grillage Beams,

  • Grillage foundations can be constructed in low time and the materials used are also low compared to other foundations.
  • The evocation of heat is been kept in control with the help of such foundations.
  • Vibrations caused in a house because of some disturbances are taken down by the grillage Foundation. It has the capability to reduce a significant amount of vibrations.
  • Grillage foundations are mostly used for important structures such as heavily loaded columns, Piers, Piles, and scaffolding work.
  • The most important benefit of a grillage foundation is that it is capable of transferring heavy structural load on a larger area of the foundation.

Read More: Raft Foundation | Mat Foundation| Types of Raft Foundation

Disadvantages of Grillage Foundation

The disadvantages of Grillage Foundation are listed below,

  • Piles Required for this foundation are needed to be inserted to a large depth.
  • The empty space left between the steel beams is essential to be heated and filled. hence skilled laborers are required.
  • In the construction of grillage, foundation excavation is to be done on the larger area which increases the construction cost.
  • The heavy uplift pressure can distribute this type of foundation.
  • The structural arrangement of the column bed is changed sometimes in grillage foundation construction.

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