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IGN 4-08-01 Issue 4 Bedding and sidefill materials for buried pipelines

This information note provides guidance on the selection and use of materials suitable for providing structural support to buried pipelines. Materials which fulfil this role are termed bedding and sidefill materials. This note deals both with granular materials graded in accordance with a particular specification, brought to the site for those purposes and excavated materials which have been selected as suitable. These are termed ‘processed granular’ materials and ‘as-dug’ materials respectively. The guidance given below covers pressure and nonpressure pipelines, either sewers or water mains. All such pipelines require adequate structural support to ensure their long term performance.

An appropriate specification for bedding and sidefill material is given in Water Industry Specification No. 4-08-02.

The use of foamed concrete or normal concrete bedding and sidefill materials is not covered by this IGN or WIS No. 4-08-02. These materials require special consideration in use.


The WUK Standards Board commissioned a review of IGN 4-08-01 and IGN 4-08-01A that concluded in March 2023 (in parallel with a review of WIS 4-08-02 and WIS 4-08-02A). The Board determined the four documents’ status should be changed from ‘current’ to ‘ageing’ since elements of the documents have been overtaken by BS, BS EN, or BS EN ISO standards. The documents also need updating to reflect the increased use of ‘as dug’ & recycled aggregates (principally crushed concrete & roadstone) and to address environmental & carbon reduction agendas. Technological advances in recycling plant & equipment should also be reflected in any update.

However, elements of the documents remain useful and they remain widely cited in key water industry specification documents (i.e. beyond WIS and IGN). These include:

  • Design and Construction Guidance for foul and surface water sewers offered for adoption under the Code for adoption agreements for water and sewerage companies operating wholly or mainly in England (“the Code”) – for example in ‘E2.25 Pipe surround materials’.
  • Civil Engineering Specification for the Water Industry (CESWI 7) – for example in ‘2.90 Pipe surround materials’.

The Standards Board encourages parties interested in seeing these documents updated to form a Task & Finish Group to that end. For further information on how achieve this contact the Board’s Technical Secretary here.

One or more ‘Common Editorial Caveats’ apply – see ‘WIS & IGN Library / Navigation & Caveats’ for details.

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