Archives: FAQs

Increasing the period of fire resistance of the compartment walls between flats beyond that specified in the Approved Document is unlikely to have any significant impact on the safety of occupants of the building and would have no discernable benefit to persons in the flat where the fire has started.

It is estimated that the provision of a BS 9251 sprinkler system within a dwelling will reduce fire-related casualties by around 70%. Whilst it would be desirable to install such systems in all dwellings it was decided that it would only be reasonable to impose this on larger buildings.

This was following analysis of the costs and benefits in the research report: The effectiveness of sprinklers in residential premises and consideration of the increased hazards for fire-fighters and other persons associated with fires in tall buildings, as discussed in the Regulatory Impact Assessment: Changes to Part B (Fire Safety) of the Building Regulations 2000 (as amended) and Approved Document B.

The 30m trigger height is considered to be a logical provision which aligns with the provisions for sprinkler protection for other building uses.

There may be alternative fire suppression systems that could be used where it can be demonstrated that a similar level of performance as would be provided by a BS 9251 sprinkler system can be achieved.

Where water mist systems are proposed the guidance contained in the BRE publication An Independent Guide on Water Mist Systems for Residential Buildings may assist Building Control Bodies in assessing such systems.

This would be a matter for the designer and the relevant building control body to consider. However, any such proposal may result in the need to upgrade the specification of the sprinkler system and the duration of water supplies.

For the purposes of meeting the provisions of Paragraph 8.14, the limit on the scope of BS 9251 to buildings below 20m can be ignored. However, the other limits such as the number of sprinkler heads per room should be observed.

In blocks which are taller than 30m in height, all the individual flats throughout the building should be sprinklered. However, it would not be necessary to provide them in the common areas such as stairs, corridors or landings.

Regulation 4 of the Building Regulations 2000 states that “building work” should comply with the applicable requirements contained in Schedule 1. Regulation 4(2)a then goes on to state that, “after the work is completed, the building as a whole should comply with the applicable requirements of Schedule 1 or, where the building did not previously comply with any such requirement, is no more unsatisfactory in relation to that requirement than before the work was carried out.”

Where an existing shop is extended such that the final floor area is greater than 2000m2 (whether it exceeded this value previously or not) then the building as a whole may be less satisfactory in relation to requirement B3(3) than before the work was carried out.

Therefore, the building would have to be either subdivided to limit the compartment size, fitted with sprinklers or some other solution would be necessary in order to satisfy regulation 4(2) in relation to requirement B3.

Regulation 4(2) must be judged against the requirements set out in Schedule 1 rather than the Approved Document. B3(3) requires sub-division of the building “to an extent appropriate” to its size and intended use and it may be that some buildings will still comply with B3(3) by virtue of its intended use even though they have been extended without further capitalisation.

Diagram 30a applies a more onerous standard than Diagram 30b, any combustible (including thermosetting) core panels should incorporate a band of material of limited combustibility 300mm wide centred over the wall.

However, an alternative approach might be to use a panel system which has been shown in a large-scale test to resist internal and external surface flaming and concealed burning.

In low-rise residential, office or assembly buildings to which Diagram 30b applies, panels with thermosetting cores can be used without any additional protection.

However, fire-stopping must be provided to seal the joint between the compartment wall and the underside of the panel. Any voids above the panel (such as where an additional roof covering is provided) should also be adequately fire-stopped.

The Department has commissioned some comparative testing of doors using these two standards. The conclusions of this work are that for the purposes of Item 2.d of Table B1(provisions for fire doors) of Approved Document B (Vol2), results from EN 81-58 tests can be accepted as equivalent to BS 476 part 22. In due course, the Department intends to publish the report from this work and amendments to the Approved Document necessary to meet the requirements of the Lifts Directive.

Item 2 of Table 3 (Maximum nominal internal diameter of pipes passing through fire separating element) now makes it clear that a uPVC pipe, up to 110mm in diameter, can pass through a wall or floor separating a dwellinghouse from an integral garage. The pipe should, however, still be fire stopped in accordance with paragraph 7.8. This would involve sealing around the pipe where it penetrates the wall or floor using a suitable material or a proprietary system as described in Paragraph 7.14.

No. Requirement B3(3) requires, where reasonably necessary, subdivision of the building with fire-resisting construction and/or the installation of a suitable automatic fire suppression system.

What is considered reasonable in any particular case will depend on the size and intended use of the building. In some cases, either sprinklers or compartment walls and floors will be necessary and other cases it may be necessary to provide both or neither. Guidance on where sprinklers should be provided is given the Approved Document.