Prohibited or deleterious materials
Prohibited or deleterious materials

The following Construction guidance note provides comprehensive and up to date legal information covering:

  • Prohibited or deleterious materials
  • What are prohibited or deleterious materials?
  • Defining deleterious/prohibited materials
  • Drafting of deleterious/prohibited materials clauses
  • Absolute obligation or reasonable skill and care?
  • Materials which later become prohibited
  • New materials and technologies

What are prohibited or deleterious materials?

Most building contracts, sub-contracts, consultants’ appointments and collateral warranties will include provisions dealing with the selection and/or use of materials (see Practice Note: Materials and workmanship in construction contracts).

It is important that, in designing, procuring and building new buildings or infrastructure, the specification and/or use of some materials is avoided. These materials are usually described as deleterious or prohibited materials.

The use of such materials is to be avoided either:

  1. because the materials themselves will fail or

  2. because they will cause the fabric of the building to fail (eg the ‘glass cancer’ of late 1990s/early 2000s) or

  3. because they may cause harm to individuals (eg asbestos)

Defining deleterious/prohibited materials

The approach taken in contracts to defining which materials are deleterious, or prohibited, and must not be used has changed over the years.

For many years, contracts would incorporate long lists of the materials deemed to be 'deleterious' which were not to be specified for use, or used, in the works. This situation was far from ideal: each employer had its own list and their lists were devised as a ‘catch all’ to be used in relation to all their projects, so were rarely specific to the work that was the subject of the contract. Often, in the context of a particular project, it was