Building the correct footing foundation is an essential part of any construction from small garden walls to large-scale building projects. This is an important step in strengthening the stability and endurance of a structure. This is a step-by-step beginner’s guide on the minimal requirements in footing foundation for any building project or extension in the UK.

Table of Contents

Foundation Design: Why Do We Need Foundations?

What Are Footing Foundations?

How Does the Load Transfer Mechanism Work?

How Are Footing Foundations Designed?

Soil Investigation

Structural Analysis

Foundation Design

Optimization

Foundation Design: Why Do We Need Foundations?

 It is no different from building foundations, which hold up and transfer loads from a structure to a hard surface or the ground below it. They give us our comfort zone, keeping us steady and level and preventing too much settlement and tilt. Get the foundation of a structure designed poorly, and you are either looking at very expensive redesigns to repair structural failure or a building that is going to cause you to your head between your legs and goodbye. All of that is to say much, much more goes into how successfully a building is designed, constructed and functions than we skin-covered hominids, although we like to think we’re in charge.

 What Are Footing Foundations?

 Footing foundations are the components that touch the ground. These components transfer the weight loads from the structure across a larger surface by minimising the direct pressure on the soil. They are made from different materials, including concrete and masonry. The three main types of footings are:

Spread Footings: Commonly used for individual columns.

Strap Footings: Connect multiple footings to distribute loads.

Pile Foundations: Used for deep support in weak soil conditions.

 How Does the Load Transfer Mechanism Work?

 The mechanism of load transfer refers to the process by which loads in the building are transferred to the soil via the foundations. When a load is applied, the forces from the load travel down through the walls and columns of the structure to the footings below. To make sure the soil supports the building properly, the footing alters the forces over a larger surface of soil than its area. This is an important consideration in the design of the footings.

How Are Footing Foundations Designed?

The design of footing foundations follows several critical steps:

Soil Investigation

Before starting the design, a thorough soil investigation is essential. This includes:

Site Surveys: Assessing the site for soil type, density, and bearing capacity.

 Soil Tests: When required, explore borehole drilling and mobile lab testing to determine physical properties and acceptable bearing capacity for proposed loads.

Structural Analysis

 Following the collection of the soil data, various structural analyses might be carried out to arrive at the net loads the foundation has to support:

Dead Loads: The weight of the structure itself.

Live Loads: Temporary loads from occupants and furniture.

Environmental Loads: Influences from wind, snow, and seismic activity.

Foundation Design

Once the analysis is complete, the actual design of the footing begins, focusing on:

Size and Depth: Determining dimensions based on load and soil conditions.

Type of Footing: Selecting the appropriate type (spread, continuous, or pile).

Reinforcement: Adding steel reinforcement to enhance the footing’s strength and stability.

Optimization

After the initial design, optimization ensures cost-effectiveness and efficiency through:

Material Selection: Choosing suitable and economical materials.

 Load Redistribution: redistribution of loads for the same action for considerable cost reduction and performance enhancement. 

Compliance with Regulations: Ensuring the design adheres to local building codes and regulations.

 Summary

 Building a footing is an integral part of a structure, and it involves a systematic and meticulous process. The complexity of the design stems from multiple interdependencies with the soil conditions, axial and lateral loads, material choices and the structural design itself. All these aspects need to be considered when designing a footing foundation to ensure both safety and longevity of the superstructure above. This tutorial is geared towards presenting the essentials of footing foundation design in a systematic fashion that mimics real-world practice. It will advance from the initial step of soil investigation to the complete structural analysis and design of the footing foundation. The: ∙ Soil mechanics: terminologies, classification and properties ∙ and pile foundations, total and partial depth ∙ Footing construction: materials and methods ∙ Axial and lateral loads: stem and footing examples ∙ Structural analysis of footings: axial, bending and shear stress Formal structural analysis of foundations is beyond the scope of this tutorial.