If the 45m rule for firefighting access in paragraph 11.2 cannot be achieved to all points within the dwelling house would the provision of a private fire hydrant directly outside the dwelling be a suitable alternative approach?

Provision of water supplies does not, on its own, reduce the physiological impact on firefighters of travelling long distances whilst carrying heavy equipment. Water from private hydrants may still need to be pumped before it can be used for firefighting.

Where it is proposed to adopt an alternative approach to meeting requirement B5 (Access and facilities for the fire service). It would be advisable to seek the advice of the fire and rescue service who can advise on the practicalities of fire fighting.

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Is the 45m rule for firefighting access in paragraph 11.2 measured from the outside or from the front door?

Guidance in both Volumes of the Approved Document Part B states there should be vehicle access for a pump appliance to within 45m of all points within dwellings. This is to take account of the actual distance that the fire fighters need to carry kit and lay hoses from the vehicle to reach a potential fire.

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Is the 45m rule for fire fighting access in buildings not fitted with fire mains measured from the outside or from the front door?

Guidance in both volumes of the Approved Document Part B states there should be vehicle access for a pump appliance to within 45m of all points within dwellings. This is to take account of the actual distance that the Fire & Rescue Service need to carry kit and lay hoses from the vehicle to a potential point of fire.

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Why is the maximum hose distance in paragraphs 16.2 & 16.3, 45m?

Our local Fire and Rescue Service appliances are fitted with hoses which are much longer than 45m.
The 45m criterion is based on the physiological demands on firefighters engaged in search and rescue and on the restrictions that may be imposed by their equipment.

When considering hose length it is important to appreciate that, in practice, hoses have a tendency to “snake” when charged thus limiting their effective length. It is also common practice to trim the ends of hoses where they become damaged. The time and effort it takes to lay out a hose may also be an important factor.

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Para 9.12 of the Volume 2 of the 2006 version of Approved Document Part B states “Where the concealed space is an undivided area which exceeds 40m (this may be in both directions on plan) there is no limit to the size of the cavity if…….”. However the comparable paragraph in Part B 2000 edition states (para 10.13) “Where the concealed space is over an undivided area which exceeds 40m (this may be in both directions on plan) there is no limit to the size of the cavity if…….”. Is the omission of the word “over” in the comparable paragraph of the current Part B deliberate?

No, this is a printing error. The word “over” should be retained as for the 2000 edition of Approved Document Part B, and so paragraph 9.12 of Volume 2 of Approved Document Part B 2006 should read: “Where the concealed space is over an undivided area which exceeds 40m (this may be in both directions on plan) there is no limit to the size of the cavity if…….”.

Cavity barriers are provided to reduce the risk from unseen fire spread within concealed spaces in accordance with requirement B3(4) of the Building Regulations. The principle of paragraph 9.12 is that it relates to a concealed space over a single undivided room (such as an open-plan office). Because the room below the space is undivided, the occupants will be able to see a fire develop and react to the changing hazard, thus cavity barriers within the space above are less important than with a cellular layout. The conditions in paragraph 9.12 are intended to reduce the risk of a fire starting/spreading in the undivided void and to prevent fire entering the void from outside the room which is not visible to its occupants.

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Could increasing the period of fire resistance to walls and floors in a block of flats be a reasonable alternative to providing a sprinkler system in blocks of flats over 30m high in accordance with paragraph 8.14?

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.

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If I provide sprinklers in a block of flats can I reduce other fire protection measures?

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.

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Paragraph 8.14 asks for a sprinkler system in accordance with BS 9251 for blocks of flats over 30m, but the scope of BS 9251 states that it should not be used in buildings over 20m in height.

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.

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Paragraph 8.14, ask for blocks of flats over 30m to be sprinklered, do all flats need to be sprinklered or just those above 30m?

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.

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If an existing single storey shop is extended so that it exceeds the maximum 2000m2 compartment size, is it necessary to install a sprinkler system?

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.

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