Steel Grillage Foundation

Grillage Foundation | Types of Grillage Foundation | Steel Grillage Foundation | Grillage Footing10 min read

Grillage Foundation

Grillage foundation is a type of foundation that consists of one, two, or additional levels of beams which are usually steel, superimposed on a layer of concrete to distribute the load over a large area.

Grillage Foundation
Grillage Foundation Diagram

It is used at the bottom of the columns. These layers are cased in concrete and at right angles to themselves. This type of foundation is usually used for significant structure, column piers, and scaffolds.

Though other types of foundations and grillage footing look similar they’re completely different. Wherever foundation transfers load from the structure to the bottom, grillage disperses significant hundreds over massive areas.


Types of Grillage Foundation

Following are the Grillage Footings types,

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

Read More: What Is Foundation Repair | 8 Types of House Foundation Repair Method | How to Fix Foundation


1. Steel Grillage Foundation

Steel Grillage foundation consists of steel joints or beams that are provided in single or double tiers. Its name defines its performance and structure because it is created from steel beams, structurally called rolled steel beams.

Types of Grillage Foundation
Steel Grillage Foundation

A minimum cowl of 10cm is unbroken on the outer sides of the external beams furthermore is higher than the higher flanges of the highest tier. The depth of concrete ought to be a minimum of 15cm.

When we tend to level the bottom and pour the concrete, we must always make sure if the compaction is finished properly Associate in Nursing fashioned a proof layer of a thickness not but 15cm. It shields steel beams from groundwater, which might result in corrosion.

Then we tend to lay the primary layer of beams over the concrete bed at a distance of 100mm to 300mm, with the assistance of pipe separators. Next, we tend to pour concrete between and around the beams of the primary tier.

After that, we tend to place the second tier of the beam at the correct angle to the primary tiers with the assistance of the apparatus. Then again, we tend to pour concrete between and around the steel beams.

Steel Grillage Foundation
Steel Grillage Foundation

By doing this, we tend to connect the steel stanchions to the higher tier with the assistance of a base plate, aspect angles, and a brace. These connecting parts are embedded within the concrete to form the joint rigid.

Steel Grillage Foundation is built of steel beams, structurally referred to as-rolled steel joists(RSJ.), provided in 2 or additional tiers. Within the case of double tier grillage(which is usually provided), the highest tier of grillage beams is arranged at right angles to a very cheap tier.

The joists or beams of every tier are commands in position by twenty-millimeter diameter spacer bars with twenty-five-millimeter diameter pipe separators. Fig. 3.10 shows the arrangement and section of such a foundation. The grillage beams are embedded in concrete.


2. Timber Grillage Foundation

Timber Grillage type foundation is provided for heavily loaded masonry walls of timber columns. This foundation is particularly helpful in soggy areas, wherever the bearing capability of the soil is extremely low and wherever the loading on the soil is restricted to 50-60 KN/m2.

Timber Grillage Foundation
Timber Grillage Foundation

Timber planks and timber beams square measure used rather than steel joists. There’s no concrete encircled between the timber joints. However, all-time low concrete provided in steel grillage is replaced by a timber platform made of timber planks.

The excavation of the bottom is leveled. An all-time low layer of timber planks of size 20-30cm, width 5-7.5cm thick is arranged aspect by aspect with no gap between them. Over the highest of this layer, a timber beam of identical section as that of the wood post is placed at right angles.

Then another layer of planks once more is arranged at right angles to the direction of beams. The higher layer of planks perhaps 7.5-10 cm. Thick, extending over the total dimension of the wall base, over that masonry wall.

Timber grillage foundation is provided for heavily loaded timber columns or masonry walls. The inspiration uses timber planks and timber beams within the place of steel joists.

This foundation is especially helpful in waterlogged areas wherever the bearing power of the soil is incredibly low, and wherever the steel beams might get unsound thanks to dirty water.

The loading on the soil is restricted to 50 to 60 kN/m2. No concrete is embedded between the timber joists. However, very cheap concrete (provided in steel grillage foundation is replaced by a timber platform created of timber planks.

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


Grillage Foundation Project

For the planning of the grillage foundation, it’s needed to calculate the masses and moments from the structure. From this, we’ve got to work out the specified base space for an appropriate allowable ground bearing pressure of the condition.

Dividing this space, we are going to conclude the numbers and size of every grillage layer. Then, we’ve got to style the layer so it cantilevers from the stinge of the layer on top of it. It’ll verify the beam sizes needed to resist the bending moments and shear forces.

The grillage can’t be boxed in in a concrete and also the order, as a result of then the composite action of the beam and concrete are discouraged. The tactic of construction and loading ought to be compatible with the planning wants


Installation of Grillage Foundation

Followings are the steps of grillage foundation installation,

  1. First, for solid monolithic grillage, we’ve got to provide and install the framework. We tend to like this grillage as a result of it’s a lot of dependable.
  2. Formwork is formed from border boards within the type of rectangular troughs. Its height is one linear unit and breadth is up to the least wall thickness of the house. It should be set concerning a 6-8 inches gap in between every grillage.
  3. Inside the formwork, we’ve got to line a framework of reinforcement’s connections victimization binding wire. The smallest amount of distance from the frame to the face of the formwork is needed to be the same.
  4. Next, the reinforcement is joined with a similar binding wire used before.
  5. Then, Concrete should be ready to victimization the concrete mixer. It’s poured within the formwork in an exceedingly continuous cycle. Fittings should be placed at a height of 25-30mm so it fully immerses in concrete.
  6. Concrete ought to be fastidiously poured to avoid unwanted cavities. When filling the surface, the surface should be leveled and left to dry. Once it’s dried, the formwork is removed. the muse is prepared currently.

Features of Grillage Foundation

  • The grill is connected to the entire foundation through the single structure and thus it contributes to an evenly distributed weight of the structure.
  • Most of the time, this foundation is organized as a monolithic reinforced concrete structure. The resistance is provided by the metallic structure (steel foundation for grilling).
  • Minimum clearance of around 8 cm is provided between the grillage beams so the concrete will be easily poured and properly compacted.
  • As the concrete filling doesn’t carry a load, it functions to keep the beams in position and prevents them from getting corroded.
  • The depth of concrete below the lower tier is kept at a minimum of 15cm.

Advantages of Grillage Foundation

Following are the Advantages of Grillage Beams,

  • The installation process of Grillage Beam requires less time and materials.
  • 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 care of with the help of the Grillage Foundation. It has the capability to reduce a significant amount of vibrations.
  • This type of foundation can be used for significant structures such as column piers, and scaffolds.
  • It is capable of transforming load over a larger area.

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


Disadvantages of Grillage Foundation

Disadvantages of Grillage Foundation are listed below,

  • Piles Required for this foundation are needed to be inserted to a large depth.
  • The space beneath the grid is required to be filled and heated, hence skilled laborers are required.
  • Excavation of a larger area is needed, which increases the excavation cost.
  • It gets affected by a larger uplift force.
  • Column alignment in this type of foundation might slightly change.

Grillage Foundation?

A Type of foundation which consists of one, two, or additional levels of beams which are usually steel, superimposed on a layer of concrete to distribute the load over a large area is called Grillage foundation

Is Grillage Foundation a deep foundation?

Grillage Foundation is known for its usage at the base of the column. This type of foundation is used for the requirement of shallow foundation in loose and dense soil. However, in the case of loose soil excavation is done to a higher depth.

Is Grillage foundation economical?

For in case of transferring heavy loads from columns to the soil of low bearing capacity Grillage Foundation is one of the most suitable foundations. In this scenario Grillage Foundation is the most economical one. It distributes the load over a larger area and resists the occurrence of shear failure.

Where are Grillage foundations used?

Use of Grillage Foundation,
1. Grillage foundations are used at the bottom of the columns.
2. This type of foundation is usually used for significant structure, column piers, and scaffolds.
3. In case of transferring heavy loads from columns to the soil of low bearing capacity Grillage Foundation is used.
4. It is used to disperse the load over a large area in a foundation for grilling.

What are the reasons for recommending Grillage foundation?

Reasons For Recommending Grillage Foundation
1. The installation process of Grillage Beam requires less time and materials.
2. Evocation of heat is been kept in control with the help of such foundations
3. It has the capability to reduce a significant amount of vibrations.
4. This type of foundation can be used for significant structures such as column piers, and scaffolds.
5. It is capable of transforming load over a larger area.

Grillage Footing

Grillage foundation is a type of foundation that consists of one, two, or additional levels of beams which are usually steel, superimposed on a layer of concrete to distribute the load over a large area.


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