Gas supplies to multi-storey timber framed buildings

Safety notice: 1/2005 Issue date: June 2005

Introduction

This notice is to highlight a recurring problem that has been identified with gas supplies to multi-storey timber framed buildings.

Background

1. The investigation of a gas release at a block of flats in Bothwell, Scotland identified that a release of gas had occurred following the fracture of a malleable iron fitting on a steel gas service, the building was evacuated. It was identified that shrinkage had occurred in the timber frame relative to the external brick shell- see diagram below.
2. The identified mode of failure was due to the imposition of excessive loads from the timber frame upon the gas service, due to the cumulative effect of shrinkage of the timber frame (this shrinkage usually occurs within the first year of construction). The effect is most notable in the upper stories - see photographs below.
3. Due to the mode of failure and the type of building construction it is possible for large volumes of gas to accumulate in the area between the external brick wall and the internal timber frame structure.
4. HSE have subsequently been made aware of a number of similar failures at other similar sites

Action required

1. The use of multi-storey timber frame construction has developed over the last ten years and buildings of up to five storeys are now more common.
2. Duty holders should identify where gas services have been installed in this situation and take action to ensure that excessive forces are not exerted upon such services. Duty holders should also ensure that measures are in place to identify the type of construction being used before installing gas services.
3. Services passing through the external brick structure and the timber frame should be designed to accommodate the differential movement between the frame and the external structure. It should be noted that this should apply to all services (gas, water, electricity).
4. Guidance for the installation of gas services in multi storey dwellings is provided in the Institution of Gas Engineers documents IGE/TD/4 (Gas Services) and IGE/UP/15 (Gas Installations in Flats).

Relevant legal requirements

The relevant legal requirements are:

• The Health & Safety at Work etc. Act 1974, Sections 2 & 3
• The Gas Safety (Management) Regulations 1996
• The Pipelines Safety Regulations 1996

Further information

Any queries relating to this notice should be addressed to:

Photograph 1 - Showing movement of timber frame (at third floor) relative to external shell.

Diagram 1 - Showing relative movement.

This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance as illustrating good practice.