What are deleterious materials?
Deleterious materials (also known as prohibited materials) are materials that are prohibited for use in a project. This could be for a variety of reasons including:
- reliability
- health and safety
- structural stability/performance/physical integrity/life-expectancy of a project
- non-compliance with regulations
- susceptibility to change/deterioration.
Within the UK government’s guidance note to the Building Regulations 2010, entitled "Materials and Workmanship – approved document 7", there are a number of suggested approaches to establish the suitability of materials.
A primary approach is to check that the materials have the relevant CE marking under the Construction Products Regulation or another EU directive/regulation (e.g. the Gas Appliances Directive). This demonstrates that the product has been assessed to EU technical standards. Alternative approaches include considering if the materials have been assessed as compliant with British Standards or have been tested by a UKAS accredited body.
Regardless of which approach is taken, it is still important to consider the detailed information that accompanies the product to ensure that the material is suitable for the intended purpose and application.
Deleterious materials, procurement and contracting approach
When selecting materials parties often need professional advice and guidance from consultants and contractors, and so a formal professional appointment or construction contract establishing the terms and scope of the consultant or contractor's work will be necessary. It is typical in relevant construction documents to include an obligation on the consultant or contractor to not specify or approve for use, use or permit to be used any product or material, which, at the time of specification or use, or are suspected to be deleterious.
The manner and scope in which such an obligation is warranted may be discussed when finalising the terms of the contract. As to how this is finally resolved is a matter for negotiation and will depend on the nature of the services/works and the circumstances of each project.
Employers and those in the supply chain will want to ensure they properly engage the relevant technical specialists at all stages of the project to help ensure that suitable materials have been specified, procured and installed.
In addition there are a number of resources at hand to help in the specification of materials – for example The British Council of Offices produces its 2011 guide entitled “Good Practice in the Selection of Construction Materials 2011”, which will often be referred to in a deleterious materials clause.
This article was written by James Horton.