Building Strong Foundations: NHBC's Recommendations for Building Near Trees

The NHBC (National House Building Council) foundation guidance provides recommendations and standards for the design and construction of foundations in residential buildings in the UK. It covers a range of foundation types, including strip, trench-fill, and raft foundations, as well as pile foundations and ground improvement techniques.

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The NHBC foundation guidance sets out the minimum requirements for foundation design and construction, as well as providing best practice advice to help ensure that the foundations are suitable for the specific site conditions, building type, and intended use. It also covers issues such as site investigation, soil testing, site preparation, and site drainage.

In addition to the general foundation guidance, NHBC also provides specific guidance for foundations near trees, which is designed to help ensure that the foundations are not adversely affected by the growth of trees and their roots, and to help protect trees from damage during the construction process.

The aim of the NHBC foundation guidance is to ensure that new residential buildings are constructed on solid and stable foundations, providing a safe and durable structure for occupants, and protecting against defects and damage over the lifetime of the building.

Designing, Protecting, and Removing Trees for Safe and Stable Residential Construction

When building near trees, hedgerows, or shrubs, it is important to take into account their physical growth, as well as the protection of any remaining vegetation and the removal of existing trees and hedgerows. The National House Building Council (NHBC) has put forward a set of recommendations for the specification of foundations near trees, which must be followed to ensure the safety and stability of the development.

Before any work can begin on a site, a survey should be carried out to record the location, heights, and species of trees, hedgerows, and shrubs on and adjacent to the site, which may affect the proposed development. If the location of previously removed vegetation is not known, local enquiries and reference to aerial photographs should be carried out. An engineer may also need to be consulted to undertake a site-specific design based on all relevant information and in accordance with Technical Requirement R5.

One of the major concerns when building near trees is the damage that can be caused by their growth and roots. To avoid this, structures and services should be located at a safe distance from the trees. If this is not possible, precautions should be taken to allow for future growth, such as reinforcing foundations to resist lateral forces, bridging walls or structural slabs over the roots, allowing sufficient clearance, or reinforcing to avoid cracking, and laying paving and other surfaces on a flexible base to allow for some movement.

Roots often extend to distances in excess of the height of the tree, the majority of which are within 600mm of the surface and project radially. All parts of the system are easily susceptible to damage, which may not regenerate and can affect the stability of the tree. Damage can be caused by stripping topsoil too close to trees, excavating trenches for foundations and services too close to trees, raising soil levels adjacent to trees (particularly where non-granular materials are used), the compaction of soil around trees by heavy plant, the storage of heavy materials around trees, and covering the rooting area with impervious surfaces.

To protect the remaining trees and hedgerows, a fence or barrier should be erected around a single trunk equivalent to a circle of radius 12 times the trunk diameter measured 1.5m above ground level. The shape of this area may change depending on specific factors such as local drainage, soil type, age, and species of the tree, and an arboriculturist may be required to assess these factors. Services should be routed away from trees, or where this is not possible, installed in such a way as to minimize root damage.

In some cases, statutory requirements, planning conditions, conservation area restrictions, or tree preservation orders may result in protected trees and hedgerows being retained. The local planning authority should always be consulted to ensure compliance with any relevant regulations. Dead trees and hedgerows should be removed, and unstable trees should be made steady or felled. Specialist advice should be obtained from a tree consultant if necessary.

In conclusion, building near trees, hedgerows, or shrubs requires careful planning and consideration. The NHBC recommendations for the specification of foundations near trees should be followed to ensure the safety and stability of the development, and to protect the remaining trees and hedgerows. By taking these precautions, it is possible to create a development that coexists harmoniously with the natural environment, providing long-term benefits for both the residents and the surrounding ecosystem.

NHBC Foundation Design: Get Precise Tree Surveying Data with Our Dedicated Assessment Services

It is worth noting that a BS5837:2012 survey can also provide the necessary information for NHBC foundation design. However, if you prefer to commission a dedicated assessment solely for the purpose of meeting NHBC requirements, our tree surveying services can help you collect the precise data needed for this purpose. By choosing to work with us, you can have peace of mind knowing that your development project is in compliance with NHBC standards, and that the safety and stability of your structures are assured. So if you need a tree survey for your upcoming project, we are here to provide you with a range of expert services tailored to your specific requirements. Please contact us to learn more about how we can help you.

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Adhering to NHBC's foundation guidance is crucial for constructing safe and long-lasting residential buildings in the UK. The guidance offers a comprehensive set of recommendations and best practices for the design and construction of foundations, including specific guidelines for building near trees. By implementing these guidelines, developers can ensure that their structures are robust and protected from the effects of tree growth, while also preserving trees and hedgerows on the construction site. If you are interested in accessing the NHBC foundation guidance documents, please visit the official NHBC website, where you will find a wealth of resources available for download.