NHBC Standards 2011

4.2 Building near trees


4.2 - M1Materials standards
4.2 - M2Proprietary heave materials

4.2 - M1
All materials shall:
(a) meet the Technical Requirements
(b) take account of the design

Materials that comply with the design and the guidance below will be acceptable for building near trees.

Materials used when building near trees should comply with all relevant standards, including those listed below. Where no standard exists, Technical Requirement R3 applies (see Chapter 1.1 'Introduction to the Standards and Technical Requirements').

References to British Standards and Codes of Practice include those made under the Construction Products Directive (89/106/EEC) and, in particular, appropriate European Technical Specifications approved by a European Committee for Standardisation (CEN).


4.2 - M2
Proprietary heave materials shall be assessed in accordance with Technical Requirement R3

Where foundations and substructure could be subjected to heave, they should be protected by voids, void formers or compressible materials in accordance with the design.

Void formers consist of material that collapses to form a void into which the clay can swell reducing the build up of load on the foundation.

Compressible material, such as low density polystyrene, compacts as the clay expands reducing the build up of load on the foundation.

Each material should be used in accordance with the requirements of the relevant independent assessment and the manufacturer's recommendations.