Building near trees

4.2
Also see:
Technical Requirements R5
BS 5837

4.2.3Building near trees

When building near trees, hedgerows or shrubs, the designs shall take account of:

  1. physical growth of young trees
  2. protection of remaining trees and hedgerows
  3. removal of existing trees and hedgerows.

Before the site is cleared, a survey is required 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. Alternatively, the design should assume the worst conditions, or an engineer consulted to undertake a site-specific design based on all relevant information and in accordance with Technical Requirement R5.

Where root growth is noted within shrinkable soil and where records are not available, an engineer should be consulted to assess whether volume change is likely.

Physical growth of young trees

Damage to foundations resulting from the growth of trees and roots should be avoided by locating structures and services at a safe distance. Where this cannot be achieved, precautions which allow for future growth should be taken which include:

  • reinforcing foundations to resist lateral forces
  • bridging walls or structural slabs over the roots, allowing sufficient clearance or reinforcing to avoid cracking
  • laying paving and other surfaces on a flexible base to allow for some movement.

Protection of remaining trees and hedgerows

Roots often extend to distances in excess of the height of the tree, the majority are within 600mm of the surface and project radially. All parts of the system are easily susceptible to damage which may not regenerate and which can affect the stability of the tree.

This 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
  • covering the rooting area with impervious surfaces.

Trees should be protected from damage by:

  • a fence or barrier. The fence or barrier should extend 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. An arboriculturist may be required to assess these factors
  • ensuring services are not routed close to trees or, where this is impractical, are installed in such a way as to minimise root damage.

Removal of existing trees and hedgerows

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 be consulted.

Dead trees and hedgerows should be removed. Unstable trees should be made steady or felled. If necessary, specialist advice should be obtained from a registered arboriculturalist.