6 12 2019 | Fire regulations | wood construction

How changing fire safety requirements in the U.K. building regulations affect the use of wood products

The Construction Products Regulation (CPR) lays down harmonised rules for the marketing of construction products in the EU. Brexit will influence the regulations concerning CE-marking and mutual recognition of the European product standards in the U.K. in this continuously evolving situation.

The building regulations in the U.K. are based on country-specific approaches and especially the fire safety requirements are currently under change. There are four sets of regulations – England, Wales, Scotland and Northern Ireland – which are developed separately. The Wood Protection Association (WPA) has given its own guidance on how to apply the new regulations.

 

BACKGROUND OF DIFFERENT FIRE SAFETY REQUIREMENTS

 

The approaches to fire regulations have been slightly different between the four U.K. countries, as they have been developed separately as a part of local building regulations. In 2017 the facade of the 20-story Grenfell Tower in London caught fire. 72 people were killed by the disaster. There were several reasons that led to this catastrophe, starting from insulation and cladding materials and ending to the lacks of functional fire safety and fire equipment maintenance.

This incident has led to processes targeting to tightening of the fire regulations. However, the approaches will vary between countries. Today it seems that England and Scotland will have very different approaches to the fire safety of buildings. At the moment it is not known what the development will look like in Wales and Northern Ireland.

 

FIRE REGULATIONS IN ENGLAND

 

The fire regulations in England are given in two documents, which contain both the regulations and recommended ways of meeting them. Part B, volume 1 applies to residential buildings and Part B, volume 2 applies to non-residential buildings.

Sections of the fire regulations in England have recently been changed to exclude combustible materials anywhere within the external wall section of buildings that are slow to evacuate (e.g. residential tower blocks, hospitals) and which have a top story height of over 18 m. This exclusion is a legal requirement and not a recommendation. Performance testing is not allowed on these high-risk buildings.

Euroclass B materials – like wood claddings with Euroclass B-s1, d0 fire protection – are still permitted above 18 m on buildings that are straightforward to evacuate. Performance testing using BS 8414 is allowed on these low-risk buildings.

Further restrictions apply near boundaries between properties and near escape stairs. Euroclass B materials are permitted near boundaries but not near escape stairs.

 

FIRE REGULATIONS IN SCOTLAND

 

The fire regulations in Scotland are also given in two documents containing both the regulations themselves and recommended ways of meeting them. Technical handbook - domestic buildings apply to residential buildings and Technical handbook - non-domestic buildings applies to non-residential buildings.

A Scottish government report published in June 2018 has given recommendations on how the Scottish fire regulations need to change. The proposal is that combustible cladding and insulation will be excluded from all buildings which have a top story height of over 11 m. Combustible cladding and insulation will also be excluded on any height of the building if evacuation in case of fire is slow. Performance testing (using BS 8414) can be used as an alternative approach.

Further restrictions apply near boundaries between properties and near escape stairs. Euroclass B materials are not permitted near boundaries or escape stairs.

 

WOOD PROTECTION ASSOCIATION GUIDANCE

 

The national Wood Protection Association (WPA) in the U.K. has recently issued a number of guides related to flame retardants and cladding. The guidance introduces quality assurance schemes for approval of products, processes, and distributors, aiming to secure the performance of fire protected timber products.

Dr. Ivor Davies from the Institute for Sustainable Construction in Scotland sees that the WPA guidance are useful, although these guides only apply to England. He also thinks that the English and Scottish fire regulations have been too lax, and the changes are to be welcomed as an opportunity because they bring the regulations into line with best practice elsewhere.

 

EUROCLASSES FOR INTERIOR AND EXTERIOR SURFACES

 

European fire testing of construction products is based on the Euroclass system, in accordance with standard BS EN 13501, with the following standardised tests:

  1. Fire technical testing of building products – non-combustibility: EN ISO 1182
  2. Fire technical testing of building products – single burning item test (SBI): EN 13823
  3. Fire technical testing of building products – ignitability test: EN ISO 11925-2

Euroclass requirements for building materials are A1, A2, B, C, D, E and F. Smoke production and the formation of flaming droplets are expressed with the additional classes s and d. The smoke production classes are s1, s2 and s3, and the formation of flaming droplet classes are 0, d1 and d2.

As an example, wood products treated with Nordtreat fire retardants fulfill Euroclass B-s1,d0. This means that the products contribute in the fire to a very limited extent, their smoke production is very limited and no flaming droplets occur.

Wood products manufacturers can CE-certify their industrial fire retardant treatment for specific products in cooperation with Nordtreat to meet fire class B-s1,d0 requirements. The fire retardant treatment can also be done at the building site according to the manufacturer’s guidance but in this case, the structure must be accepted by the local building authorities.

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