New water mist systems guidance from The Welsh Government

water mist

The Welsh Government has published new guidance on water mist systems aimed at local authority building control and installers to assist compliance with building regulations.

This new guidance sets out how installers of water mist systems can satisfy the requirements of Regulation 37a of the Building Regulations 2010.

Automatic fire suppression is mandatory in new residential premises in Wales. New legislation in 2011 led to changes in the building regulations that came into force in 2013.

The BRE was commissioned in January 2019 to write this guidance for the Welsh Government. It is primarily intended for use by Building Control Bodies to assist them in assessing water mist systems for new and converted domestic and residential buildings in Wales.

A water mist system is a fixed fire protection system, comprising components for automatic detection and actuation, water supply, delivery and water atomisation. A water mist system discharges a spray of small water droplets from the operating nozzle(s).

The guidance is also of interest to automatic water mist system manufacturers, designers and installers as it details the essential information and supporting data required by Building Control Bodies. This guidance suggests when it may be appropriate to obtain independent specialist advice.

It contains a flow chart that shows key stages in the design, installation and commissioning of a BS 8458 water mist system, the necessary communications with the Building Control Body and the key documents that the designer and installer will need to submit to the Building Control Body for the purposes of evaluating the water mist system design for the building.

There is also a checklist of questions for the designer, installer and commissioner of the system to provide to Building Control Bodies confirming compliance with the installation standard.

First published by the Fire Protection Association:


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