The NHBC’s Richard Smith shares some of the key learnings from its latest report, which looks at how to futureproof foundations against climate change.

The NHBC Foundation is committed to providing high quality research and practical guidance to support the house-building industry, with particular focus on the challenges faced by the modern developer. As climate change continues to be of interest across all sectors, the NHBC Foundation identified new homes foundations-planning for climate resilience as a key concern for the sector.

The Foundation Solutions report ‘Future Proofing Against Climate Change’ explores the increasingly important issue of foundation design in housebuilding and its application in making new homes more resilient to the effects of extreme weather caused by climate change. The report concentrates on challenges in three important areas:

• highlighting potential risk factors associated with climate change
• recognising government policies aimed at promoting an increase in tree/canopy cover within new developments 
• understanding the carbon footprint of foundation systems and how these can be assessed and reduced.

Building Foundation Solutions – Future Proofing Against Climate Change provides an overview of what we currently know, including relevant legislation and policy drivers for change, the major risks to building structures and their foundations from climate effects and, of course, how to mitigate them. 

UNDERSTANDING THE RISK OF CLIMATE CHANGE TO FOUNDATIONS

Foundation planning is a vital aspect of any build and getting this right contributes to the integrity, resilience and longevity of a new home.

In June 2021 the UK Climate Change Committee published a report titled ‘Independent Assessment of UK Climate Risk’ which looked at climate change risks and opportunities in the UK, alongside statutory adaptation advice for the UK government. It concluded, for a 2°C increase by 2100, annual damage from flooding for non-residential properties across the UK is expected to increase by 27% by 2050 and 40% by 2080. For a 4°C increase, this rises to 44% and 75% respectively over the same timescales.

In addition, ‘risks to building fabric’ are identified in the same report as one of 20 risks assessed as requiring further investigation at a UK-wide level. The magnitude of the risks to building fabric are categorised as ‘High’ (defined as hundreds of millions of pounds per annum) in the 2050s and ‘Very High’ (defined as over £1bn per annum) in the 2080s. These sobering predictions alone should be enough for developers to consider the long-term viability of the homes being built considering climate change and were key factors in the NHBC Foundation identifying foundation design as a significant area of interest.

THE IMPACT OF TREE/CANOPY COVER

Tree canopy, which includes the area of leaves, branches and stems of trees, is not necessarily an immediate consideration when it comes to the design of housing foundations. 

Although both newly planted and established trees pose direct and indirect risks to building foundations, trees are often a welcome inclusion in a development for both environmental and aesthetic reasons. Developers should also be considering the wider impact increased canopy cover can have as research suggests even moderate increases in canopy cover within cities can aid adaptation to the adverse effects projected under a changing climate.

Correctly managed trees contribute to the planning, design and organisation of sustainable, resilient landscapes, as they help make developments safer and more attractive. However, the impacts of increasing canopy cover on building foundations need to be considered as canopy cover within new development layouts should be designed to ensure space for future growth of roots, stems and canopies to maturity, mitigating risk of direct contact to structures, causing obstruction of access, light or nuisance – as noted in BS 5837:2012 the aim should be to “achieve a harmonious relationship between trees and structures that can be sustained in the long term.”

REDUCING THE CARBON FOOTPRINT

The first step in being able to reduce the carbon footprint of foundation systems is to recognise that foundations represent a substantial component of carbon emissions relating to construction and can therefore make a significant impact in the drive towards net zero.

The Building Foundation Solutions report examines the range of low carbon foundation solutions that are currently available, including the use of lower carbon cement products or alternatives to cement that could result in a carbon reduction of up to 50% compared to standard concrete. Reducing carbon within foundations can be achieved in a variety of other ways, including using Modern Methods of Construction (MMC), the increased use of timber both in the substructure and superstructure, as well as potentially retaining and reusing existing foundations where appropriate.

The report also looks at the interactions between low carbon design, construction solutions and climate change resilience. And, to help illustrate the issues and solutions covered, case studies are included throughout. 

The report is available to download for free now from NHBC Foundations website or by scanning this code: 

Richard Smith is head of standards, research and technical competency at NHBC