Building Regulations Update for England: Part B – Fire Safety

By Martin Edwards

Three years have passed since West London was lit up by the horrifying spectacle of the 67m high Grenfell Tower burning from top to bottom in the UK’s worst-ever peacetime building fire, which resulted in 72 deaths.

Further serious, but non-fatal, fires have since occurred in England. These have included a range of external cladding materials – timber cladding, timber balconies, high-pressure laminate (HPL) cladding – and none of the buildings was over 18m tall to the floor of the top storey.

On 9 June 2019 a severe fire, believed to have been started by a barbeque, rapidly consumed the timber-clad balconies of a 5-storey block of flats in Barking, destroying 20 flats and damaging 10 others.  The balcony floor and balustrade material was a heat-treated timber.

On 15 November 2019, a fire in a block of student flats in Bolton spread over its HPL cladding, completely destroying the top floor of the block.  The building had 7 storeys, but is reportedly designed to be just under the critical 18m height to the top floor level.

The UK construction industry continues to be focused on the fire and life safety challenges associated with the existing building stock and new construction.

Amendment to regulations and guidance

Following the Grenfell Tower fire, the UK government commissioned Dame Judith Hackitt to carry out an independent review of building and fire safety regulations and their effectiveness.  The final Hackitt report, “Building a Safer Future”, was published on 17 May 2018.  Amendments to Building Regulations and associated guidance have followed.

The Hackitt recommendations focused initially on new and existing high-rise residential buildings 10 storeys or more in height, but added:

“… a reasonable ambition might be for government to widen the definition in due course to include a wider set of residential buildings below 10 storeys or other residential buildings where people sleep (such as hospitals or care homes) which are normally less than 10 storeys high and will have vulnerable people sleeping within them.”

The Building (Amendment) Regulations 2018

The 2018 amendments to the Building Regulations 2010 and to Approved Document B Fire Safety (“ADB”), and the publication of ADB 2019, were in direct response to Grenfell.

The Building (Amendment) Regulations 2018 came into force in England on 21 December 2018.  New Regulations 7(2), 7(3) and 7(4) contain detailed and prescriptive technical requirements, conspicuously unlike the broad functional requirements of Schedule 1 to the Building Regulations 2010, which they amend.

All external wall materials, other than exemptions listed in Regulation 7(3), must now be classified A2-s1, d0 or A1 to BS EN 13501-1: 2007 (amended 2009).  The fire classification requirements are more demanding and more widely applicable than previously advised in ADB 2006 and they are mandatory requirements, not merely recommendations as in ADB 2006.

The amendments effectively banned the use of combustible cladding in external walls of certain tall buildings, but only applied to “relevant buildings”, defined as:

“ (a)  a “relevant building” means a building with a storey (not including roof-top plant areas or any storey consisting exclusively of plant rooms) at least 18 metres above ground level and which –

(i)   contains one or more dwellings;

(ii)  contains an institution; or

(iii) contains a room for residential purposes (excluding any room in a hostel, hotel or boarding house); and

(b) “above ground level” in relation to a storey means above ground level when measured from the lowest ground level adjoining the outside of a building to the top of the floor surface of the storey.”

The reason for excluding hostels, hotels and boarding houses (places where people sleep and may be unfamiliar with the building) from the list of “relevant buildings” is not stated.  However, a government consultation paper published in June 2018 stated that hotels have different evacuation strategies from residential buildings and the risks are lower.  Hotels are likely to be staffed and to have simultaneous or phased full evacuation strategies.  Blocks of flats usually have a “stay-put” or “defend-in-place” evacuation strategy, where the residents stay in their dwellings unless instructed to leave by the fire service.

The mandatory requirements for “relevant buildings” (not all tall buildings) also include “specified attachments”:

“Specified attachment” means—

i. a balcony attached to an external wall;

ii. a device for reducing heat gain within a building by deflecting sunlight which is attached to an external wall; or

iii. a solar panel attached to an external wall.”

Under the amended Building Regulations, external walls of a “relevant building” containing combustible insulation or cladding that together meet the performance criteria given in the BRE Report Fire performance of external thermal insulation for walls of multi storey buildings (BR 135) for cladding systems using full scale test data from BS 8414-1: 2002 or BS 8414-2: 2005, are no longer accepted as compliant.

For a “relevant building”, the Building (Amendment) Regulations 2018 accept neither desktop study reports from fire specialists, nor a fire engineered approach to BS 7974, as options for demonstrating compliance with Part B4 (1) of Schedule 1 to the Building Regulations 2010, although these approaches were previously accepted by Building Control bodies prior to the Grenfell Tower fire.

The Building (Amendment) (Wales) Regulations 2019 are very similar to the Building (Amendment) Regulations 2018 in England, but only include balconies and solar panels as “specified attachments”, not shading devices (brises soleil) as in England.

Approved Document B (Fire Safety)  (2019)

ADB 2019 took effect on 30 August 2019 for use in England, not Wales.       (Wales has continued with ADB 2006 edition.  Volume 2 in Wales now incorporates 2010, 2013, 2016 and 2019 amendments.)

ADB 2019 is published in two volumes as previously, but the contents have now been changed to:

Volume 1,      Dwellings;  (including blocks of flats)

Volume 2,      Buildings other than dwellings.

The Main changes in the 2019 edition states that:

Approved Document B has been redrafted to clarify its language and content in line with the Department’s style guide for approved documents.  … There are no changes from the previous edition to the technical guidance within Approved Document B.”

However, there were very significant amendments to ADB 2006 in November 2018 and further amendments in December 2018 and April 2019, so the user of ADB 2019 should not make any assumptions, but read the advice carefully.

In addition, ADB 2019 was corrected in September 2019, soon after it came into effect.  The corrected issue is superficially indistinguishable from the first issue, but note that the more recent version has the list of Main changes in the 2019 edition and an index at the end.

Clarity of language was a 2013 recommendation to the government by the Coroner following the Inquest into the fatal Lakanal House fire in 2009.

ADB 2019 has been significantly restructured and re-ordered, so the guidance may not be in the location with which the reader is familiar.

The design of blocks of flats has moved from Volume 2 to Volume 1 in ADB 2019.  Volume 1 now includes recommendations for flats in addition to houses, and as a result, has sacrificed the brevity of ADB 2006 Volume 1.

Both ADB 2019, Volume 1: Dwellings and Volume 2: Buildings other than dwellings, reproduce the 2018 amended Building Regulation 7, confirming the ban on combustible materials in the external walls and specified attachments of “relevant buildings” with a storey 18m above ground level.  In “relevant buildings”, Class A1 or A2-s1, d0 materials are obligatory in the construction of the external walls.  (ADB 2019 uses European “Reaction to fire” classes as in BS EN 13501-1 and no longer national classes.)

Regarding components exempted in Regulation 7(3), sub-paragraph 12.16a states that, for a “relevant building”, membranes used as part of the external wall construction should achieve a minimum classification of European Class B-s3, d0.  There are already breather membranes and waterproofing membranes on the market that meet this requirement.  However, there is no definition of the term “membranes” and no guidance as to whether the advice includes vapour control layers (VCLs), which would be more difficult to achieve.

In tall buildings (top storey more than 18m high), other than “relevant buildings”, there is now an unambiguous recommendation in ADB 2019 (paragraph 10.6 of Volume 1 and paragraph 12.6 of Volume 2) that both the insulation and the core of the cladding panels should be the European equivalent of the old national classification “limited combustibility”:

“ In a building with a storey 18m or more in height … any insulation product, filler material (such as the core materials of metal composite panels, sandwich panels and window spandrel panels but not including gaskets, sealants and similar) etc. used in the construction of an external wall should be class A2-s3, d2 or better.”

(Note that the amendment in the guidance regarding materials and products to include specifically the core materials of metal composite panels, sandwich panels and window spandrel panels has not been applied to ADB in Wales.)

The former Appendix F: Fire behaviour of insulating core panels used for internal structures, has been largely eliminated in ADB 2019.  This appendix was introduced to ADB 2000 in response to the fatal 1993 fire at Sun Valley Poultry, Herefordshire, amongst 30 UK fires involving composite panels during the 1990s.

Appendix F was based on early UK metal-faced composite panel experience with much thicker (typically 50–100mm) foam polymer cores.  ADB 2000 and ADB 2006 explained the fire behaviour of composite panel materials and fixing systems, including degradation of polymeric materials, delamination between the facing and the core material, loss of structural integrity, concealed fire spread, toxic smoke production and rapid fire spread, much of which is common to external cladding and valid for thin ACM panels with PE cores.  However, all of the explanatory content has been removed from ADB 2019 and only a few recommendations, in the context of internal wall and ceiling linings, survive in paragraph 4.10 of Volume 1 and paragraph 6.11 of Volume 2.

The new ADB 2019, Volume 1: Dwellings, retains the “stay-put” evacuation strategy for blocks of flats and explains:

“ Provisions are recommended to support a stay put evacuation strategy for blocks of flats.  It is based on the principle that a fire is contained in the flat of origin and common escape routes are maintained relatively free from smoke and heat.  It allows occupants, some of whom may require assistance to escape in the event of a fire, in other flats that are not affected to remain.

Sufficient protection to common means of escape is necessary to allow occupants to escape should they choose to do so or are instructed/aided to by the fire service.  A higher standard of protection is therefore needed to ensure common escape routes remain available for a longer period than is provided in other buildings.”

Blocks of flats usually have a “stay-put” evacuation strategy and it has worked well for many years, but it is dependent on effective compartmentation, which failed at both Lakanal House (2009) and Grenfell Tower (2017).

The recommendations regarding common escape routes in blocks of flats are substantively unchanged, despite post-Grenfell lobbying.  Subject to specified provisions, a single escape route and a single common stair are acceptable.

Part B3 of ADB 2019, Volume 1, does not include the advice in ADB 2006 regarding car parks, although car parks are very often included in blocks of flats.  The first fatal UK car park fire occurred in a block of sheltered flats over a semi-basement car park in Bristol in 2006.  The guidance for car parks is included in ADB 2019, Volume 2, Section 11, largely unchanged since 2006.

As first published, ADB 2019, Part B3, paragraph 7.4, recommended sprinklers for blocks of flats with a floor more than 30m above ground:  the same advice as in ADB 2006, despite much lobbying from the fire service and others.  This recommendation has just been revised:  see May 2020 amendments following.

ADB 2019 edition, May 2020 amendments

The changes to the guidance focus on fire safety provisions in blocks of flats and therefore apply principally to ADB 2019, Volume 1.  Note that the critical height at which the recommendations apply is top storey more than 11m above ground level, i.e. a 4 or possibly 5-storey block.

a. Sprinklers: A reduction in the trigger height from 30m to 11m.

Paragraph 7.4 now states:

“ Blocks of flats with a top storey more than 11m above ground level (see Diagram D6) should be fitted with a sprinkler system throughout the building in accordance with Appendix E.

NOTE:  Sprinklers should be provided within the individual flats, they do not need to be provided in the common areas such as stairs, corridors or landings when these areas are fire sterile.”

Table B4 Minimum periods of fire resistance, item 1. Residential: a. Block of flats – without sprinkler system, is also amended to read “Not permitted” for buildings with height of top floor above ground of more than 11m.

b. Wayfinding signage for the fire service:  A new recommendation for floor identification and flat indication signage within blocks of flats with storeys over 11m.

New paragraphs 15.13 – 15.16 are devised to assist the fire service to identify each storey from the firefighting stair and firefighting lift, and the location of each flat.  There are provisions to ensure the legibility of the signs in low level lighting conditions.  The difficulty in reading signage in smoke conditions has affected many firefighting operations, including Grenfell.

There are conventions for numbering the floors, which are intuitive and in common use in the UK, but may be unfamiliar to residents from other countries.  Flat indicator signs are recommended, sited immediately below the floor identification signs.

However, there is no convention recommended on flat numbering, so the flat number does not have to derive from the floor designation number, although most building designers and managers already do this.

A note reads:  In the case of multi-storey flats with two or more entrances, the flat number should only be indicated on the normal access storey.”

Two recent fatal fires (Lakanal House 2009 and Shirley Towers 2010) involved “scissor flats”, in which individual flats cross the width of the block spanning over and under the central corridors, so all sleeping accommodation is on one side of the block and all living spaces are on the opposite side.  At Shirley Towers, the fire flat, No. 72, had its entrance on the 9th floor and a fire exit on the 11th floor, giving the fire service a logistical headache.  Firefighters normally set up their operational bridgehead 2 storeys below the fire floor, so this was on the 7th floor, but the lift operator understandably delivered colleagues only to the 5th floor.

The amendments apply in England and take effect on 26 November 2020.  (Wales already has more demanding requirements for fire suppression systems.)

Learning from recent fires

In the fire on 9 June 2019, which consumed the timber-clad balconies of a 5-storey block of flats in Barking, the balcony floor and balustrade material was a heat-treated timber that achieved only Class D to BS EN 13501.  There is still no provision against such use of timber cladding on buildings less than 18m tall in ADB 2019, but there is now advice in MHCLG “Advice for Building Owners of Multi-storey, Multi-occupied Residential Buildings” (Jan 2020) to remove and replace balconies constructed of combustible materials.

The block of student flats in Bolton, where fire spread over the HPL cladding on 15 November 2019, was a building just under the critical 18m height to the top floor level.  This being the case, it should have had Class B-s3, d2 cladding on the top storey over 18m above the lowest adjacent ground level, and below 18m the cladding should have been Class C-s3, d2.  Standard HPL cladding typically has a Class D reaction to fire performance.  MHCLG “Advice for Building Owners of Multi-storey, Multi-occupied Residential Buildings” (Jan 2020) now recommends remediation of HPL cladding for some tall residential buildings and for hospitals and care homes, but even so does not apply to the Bolton building.

Of the various serious fires which occurred during 2019, none of the buildings was over 18m to the floor of the top storey, so the Building (Amendment) Regulations 2018 would not apply to them. Given that most of the new recommendations in the 2019 edition of ADB apply only to 18m+ tall residential or institutional buildings, this raises the question of whether the guidance should extend to other building types and to buildings that are less tall.