Understanding The Types Of Building Footings Through Forensic Structural Engineering

Do you know what the common types of footings are used for Australian residential buildings? This blog explores the importance of footings and their role in distributing the building loads. We will look at how soil conditions affect the choice of footings.

There are four types of footings commonly used in residential buildings in Australia. Like the Strip/Stump Footing, Reinforced Concrete Slab, Suspended Slabs on Piers and Slab on Ground.

Partner with a trusted consulting firm that provides forensic structural engineering services in Brisbane. They can help you understand the soil condition and recommend the best footing for your building.

Why is Footing Required?

A footing is an important part of any building. It plays the role of a mediator between the load of a building and the ground on which it is standing. Walls can soon start misaligning without a well-designed footing. Even the floor becomes prone to unevenness due to soil movement and water damage. Footing also plays a crucial role in resisting mild tremors from earthquakes.

Load Distribution and Building Stability

Footings help in distributing the building’s load uniformly across the ground. It protects the building from soil moisture and expansion. The buildings gets and anchor against the high winds. Some building’s footing even hold mechanical systems. Therefore, footings ensure that a building is always stable and safe.

Different Types of Foundation Soil that Impacts Drainage and Stability

A foundation is simply the soil on which the building is standing. It takes the entire weight of the building. Therefore, it’s crucial to assess the soil condition before tagging it as the building’s foundation. Forensic structural engineering services will help you evaluate soil conditions and design the footing accordingly.

Stability and drainage depend on the type of foundation soil. Usually, footings on sandy foundations tend to settle evenly and quickly. Sandy foundations are also good for drainage as they absorb water very well. On the flip side, footings on bedrock foundations will require time to settle.

A clay foundation for any building is too volatile. It absorbs water significantly and reacts to weather changes. Clay soil tends to expand 50% in drier climates and shrink by the same rate. The constant movement can cause a problem for any building style.

The Role of Forensic Structural Engineering Services for Reliable Footing Design

A thorough structural investigation proves a lot. The experts can provide the necessary information about the soil limitations, behaviour and type. This allows the engineers to design a befitting footing. This prevents the chances of building and development complications in future.

Different Types of Footings in Australia

1. Strip Footing

Strip Footing is the most common type of footing in Australia. Concrete is often used for the stumps. Concrete is also a recommended material for complying with design requirements and construction regulations. There are two major categories in this footing system:

• A sequential line of rectangular concrete

• Isolated posts (stumps) to provide support on the footing’s pad.

Strip footing consists of a sequential line of stumps that support the external walls. The isolated stumps are strategically placed to support the internal floors. This footing system is applicable for sloping and flat sites.

2. Reinforced Concrete Slab

Reinforced concrete raft slabs are strong and durable. This is a shallow footing system that consists of raft slabs. This is also one of the commons in the Australian Footing system. The concrete beams provide integral support and strength to the building's base. They can be positioned and spaced according to the project’s needs.

This type of footing is generally applicable to unstable and difficult ground conditions. Consult forensic structural engineering experts to assess suitability. The raft slaves that are widely used in Australia:

A. Stiffened Rafts

Stiffened rafts are made from 100mm-thick steel. They are reinforced slabs with strong external and internal beams. These are embedded in the foundation to acquire extra support and strength. The edge thickness of the raft may vary between 300mm and 1100mm.

B. Waffle Raft

Waffle rafts are becoming increasingly popular in Australia as builders look for faster, cheaper, and easier building processes. The thickness of these slabs usually extends to 85mm. This is further supported by ribs. The ribs are edge beams that are placed around the perimeter. The ribs are actually internal beams that run in a crisscross pattern. The pattern creates a waffle-like shape. Waffle slabs can be placed directly on the ground over natural soil or compacted fill. However, they may become problematic on reactive soil which can only be optimised with proper Forensic Structural Engineering services in Brisbane.

3. Suspended Slabs on Piers

Suspended slabs on pier are specifically designed for problematic sites. Foundation soil with reactive properties is not suitable for any building project. Therefore, installing deep concrete piles is the best option to achieve significant support. These are used to support concrete raft slabs and transfer the load to the soil or bedrock. Suspended slabs help transfer the load beyond the depth of problematic soil layers. Forensic structural engineering services are often used to determine the reactive layers of a foundation.

4. Slabs on Ground

Reinforced concrete is used in the design of a slab-on-ground footing system. Each slab is approximately 80mm thick. The edges of the slabs are slightly thicker to promote stability. Waterproofing plastic and crushed gravel are used to make the slabs. This prevents moisture from seeping through the ground. This type of footing system is suitable for non-habitable areas like driveways and garages.

Choosing the Right Footing System for Your Project

We can already see that various factors contribute to the choice of the footing system. A forensic structural engineering expert can uncover the pros and cons of a foundation and recommend the most appropriate footing system. They can help you design the perfect footing by eliminating costly expenses associated with soil movement.

Fernandes & Associates Pty Ltd. is an experienced & professional consulting firm. We specialise in assessing the mechanical, hydraulic and structural safety. We excel in vibration and fatigue analysis, roof drainage systems, quality management systems, crane inspections and more. We are a qualified team of forensic engineers who can propose feasible solutions to engineering and workplace safety issues.