Changes to BS 9251:2014 to version BS 9251:2021. What does it mean for current and proposed residential developments?

The new BS 9251:2021 came into effect 30 June 2021 and will have implications for performance specifications for all sprinkler systems to date where the installation of the sprinkler system has not yet commenced on site.

There has been an introduction of a fourth category of system to cater for taller residential buildings (greater than 18 m) and higher risk scenarios.

The rationale for this is for the following:

1. Alignment with Fire and Rescue Service national operational guidance e.g. access and response time.
2. Consistency with BS EN 16925 (Fixed firefighting systems – Automatic residential sprinkler systems – Design, installation, and maintenance)
3. Greater risk profile in higher-rise buildings, including the need for improved resilience.

The emphasis on larger capacity minimum water supplies for taller buildings and high-risk scenarios.

1. BS 9251:2021 introduces a fourth category of system for residential sprinkler systems. The new Category 4 system should be applied to all residential buildings that have a height to the topmost occupied storey of 18m or higher.
2. A Category 4 sprinkler system is generally as per a Category 3 system with the following uplifts:
   
   - 60-minute water supply duration.
   - Should be provided with two or more tanks, each capable of providing 50% or more of the required water supply to the system.
   - Be provided with a backup power supply and automatic changeover functionality.
   - Where the system is mains fed the mains should have the following provisions; where fed from a single main, the main should be fed from both ends and each end is capable of satisfying the flow demands of the system (for mains fed from one end, the sprinkler system should be fed from two or more water mains;); each feed should be capable of satisfying the flow demands of the system.

Revisions to the required areas to be covered via sprinkler protection.

1. “Where communal areas/corridors are managed areas and considered to be sterile within a fire strategy report and with agreement by the AHJ, the number of design sprinklers can be limited to two in these areas only”. The implication of this is that communal corridors are to be provided with sprinkler protection.
2. Bathrooms, shower rooms and toilets with a floor area less than 5m2are now only exempt if they have “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;”. Therefore, bathrooms under 5m2 may now require sprinkler protection based on the updated wording.
3. Staircases are now only exempt if they contain materials confirming to “BS EN 13501-1:2018, Class B-s3 or better for construction materials and B(fl) or better for flooring, including subcategories such as d0, d1, d2 for construction materials and s1 and s2 for flooring, surface spread of flame and constructed as afire-resistant separation” Therefore, in low-rise residential buildings which have been constructed with timber stairs, or in other staircases where surfaces do no achieve these requirements (e.g. concrete stairs with combustible floor coverings such as carpet that do not achieve the B(fl)-s2 rating), sprinklers may need to be extended into the staircases.
4. BS 9251:2021 includes additional guidance on the provision of residential sprinkler systems in non-residential areas as well as residential ancillary accommodation (such as bin stores, storage rooms, car parks) subject to a maximum area of 100m2 per compartment.

The non-residential accommodation that falls within the scope of BS 9251:2021 edition are as follows (accommodation not listed below would require protection via either a BS EN 12845 sprinkler system or other suitable suppression system):

• One or two car garage, where sprinkler protected, attached to a dwelling
• Car parking within or beneath a block of flats
• Bin store within or beneath the flats
• Limited office areas (e.g. concierge or site management)
• Residents’ storage sheds/tenant stores
• PTSN/CCTV/Electrical Rooms
• Plant Rooms
• Domestic laundry/utility room
• Laundry (with storage and processing of linen, e.g., institutional, care home)
• Domestic kitchens
• Hairdressing rooms
• Retail (e.g., shop or kiosk)
• Foyer/reception
• Bar/restaurant/café
• Kitchens in student hub accommodation (e.g., self-catering)
• Kitchens in residential care or other similar premises, e.g., care home

If you have any queries with regards to the information above or the new BS 9251: 2021 changes. We would recommend contacting your applicable consultant. We have not commented here on changes to the standard that would affect the technical design of a sprinkler system.

These changes should be reviewed and addressed on a project-by-project basis by the appointed sprinkler subcontractor on the relevant project. 

Thanks to Orion Fire Engineering for the relevant update summary.

Copies of BS 9251:2021 Fire Sprinkler Systems for Domestic and Residential Occupancies. Code of Practice are available on the BSI’s website.