Introduction

Sprinkler design is typically a complex and specialist task. The purpose of this technical bulletin is to outline the main changes between the previous British Standard Guidance and the Updated British Standard Guidance, particularly focusing on the design of sprinkler systems to residential buildings.

The previous British Standard Guidance, namely ‘BS 9251: 2014 – Fire Sprinkler Systems for Domestic and Residential’ was the initial code of practice and was the main British Standard covering fire sprinklers in the United Kingdom. This British Standard set the minimum requirements for the design, installation, and commission of a fire sprinkler system specifically for domestic and residential occupancies. In June of 2021, this British Standard Guidance was updated (now BS 9251: 2021). It is important to stay on top of these regulation changes, which is why a summary of changes will be outlined below.

Summary of Changes

One of the main reasons for the updated British Standard is to cover residential buildings which are greater than 45 metres in height. BS 9251:2021 has therefore introduced a new Category 4 system that applies to all residential buildings that are more than 18 metres high. A Category 4 sprinkler system is generally as per a Category 3 system with the following uplifts:

Ø  60-minute water supply duration

Ø  Should be provided with two or more tanks; with each being capable of providing 50% or more of the required water supply to the system

Ø  Be provided with a back-up power supply and automatic changeover functionality

Table 1 & 2, extracted from the updated BS, classifies the additional category (category 4) of system based on the occupancy, size and height of the building and its minimum design parameters.

BS 9251:2021 also includes additional guidance for non-residential areas and ancillary accommodation, such as bin stores, storage units, and car parks, subject to a maximum area of 100 metres squared per compartment. In larger compartments, it recommends that a commercial standard system designed to BS EN 12845 is adopted.

There is further guidance on where sprinklers can be omitted.  This is generally more restrictive than the previous guidance. BS 9251:2021 states that:

Ø  communal corridors and stairs may need to be sprinklered depending on the specification of the materials lining the walls and floors.  It is noted that this contradicts advice in the Building Regulations Approved Document B which clearly states that these areas do not need sprinklers.

Ø  Bathrooms smaller than 5 metres squared need sprinklers unless wall linings conforming to BS EN 13501-1:2018 Class A1, A2-s3,d2 and B-s3,d2, and which are not prepared for white goods such as washing machines, dryers, electric showers or water heaters.

Ø  Cupboards and Pantries with a floor area of less than two metres squared, or where the least dimension does not exceed one metre squared, are no longer exempt unless they are “not prepared for consumer units or electrical equipment (excluding a single light)”. As an example, this would mean small utility cupboards that contain a washing machine would require sprinkler protection even if less than two metres squared.

Conclusion

In conclusion, it is important to take note of the updated British Standard Guidance when focusing on buildings that are classified as category 4 or are greater than 45 metres in height. The previous British Standard Guidance did not account for buildings greater than 18 metres, which is now updated as a category 4 building. It is also important to follow when working on specific non-residential areas and must be noted when following the new guidelines on where sprinklers can be omitted.