BS 9991 Fire suppression clauses

The most recent design guide aims to complement BS 9999, which excludes individual dwelling houses from within
its scope. BS 9991 maintains the design flexibility shown in BS 9999 and recognises the strength that AWFSS can
bring. Importantly water mist systems get conditional approval providing (subject to AHJ agreement).

5.2.1.2. Multi-basement buildings
For dwellings with multiple floors below ground level, a protected stairway and an AWFSS, 9m metres should not be exceeded for from the
foot of the protected stair to any habitable room

6.3(c) Dwelling houses with one or more storey greater than 4.5m in height (three storeys)
Open plan arrangements on the ground floor can be achieved on condition that AWFSS are installed throughout the property in addition to a fire rated partition and door at first floor level.

6.4.(b) Dwelling houses with one or more storey greater than 7.5m in height (four storeys)
A second, separate protected stairwell is not required if AWFSS are fitted throughout.

6.5.2. Loft conversions
Open plan arrangements on the ground floor are permissible should AWFSS be installed throughout, in conjunction with a fire resisting partition and door at first floor level.

9.1(d) Internal Planning of Flats and Maisonettes
Flats or maisonettes with an open plan arrangement and more than one floor should have a protected stairway and AWFSS fitted. This allows
escape to the shared external entrance.
9.3(b) Provision of inner rooms in flats not more than 4.5 m in height
Inner rooms are not suggested unless the use of an AWFSS is utilised throughout the entire building, along with a grade D LD1 fire detection and fire alarm system in accordance with BS 5839-6:2013.

9.4.2(a) Extended travel distances within an open-plan flat
Flats more than 4.5m above ground level that are entered on the same level can increase total travel distances to the entrances from 9m to20m with the use of an AWFSS throughout the entire building, along with an LD1 fire detection and fire alarm system in accordance with BS 5839-6:2013.

9.5.2(d) Maisonettes with floors greater than 4.5m
No requirement to provide a separate means of escape if the maisonette has a protected stairwell and a fully fitted AWFSS.

9.7 Open Plan Layouts
Open planned flats are permissible with a fully fitted AWFSS.

11.1 Flats where occupants are not capable of independent evacuation
It is possible to use provisions of an AWFSS where the use of the building is required for people not capable of independent evacuation
(excluding common corridors and stairways.)
It is further possible to protect common areas (excluding common corridors and stairways,) using provisions of an AWFSS where the use of the
building is required for people not capable of independent evacuation.

19.1.2 Vehicular Access
Access can be increased significantly if an AWFSS is installed and where the arrival time for the fire service is not more than ten minutes:
– 90m for houses less than 4.5m in height.
– 75m for houses/flats not more than one floor above 4.5m.

23.1 Extra care housing
Extra care housing must be fitted throughout with an AWFSS.

23.2 Travel distances
If an AWFSS is fitted throughout a block of flats, then travel distances can be doubled on common escape from 7.5m to 15m and 30m to 60m

29.4.2 Boundary Distance
Boundary distances can be reduced by 50% with a fitted AWFSS.