The LWF Blog

Fire Safety Engineering for Design – Sprinkler Protection – Part 223

February 24, 2025 11:38 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 222, LWF considered the rules and standards for sprinkler installations. In part 223, we continue to discuss exceptions to sprinkler protection throughout a building.

Although it is commonplace for sprinkler installations to be installed throughout a building, there are situations where it would be hazardous for sprinklers to operate and therefore, installation in that part of a building would be inappropriate. A kitchen area may be one of these, if it had metal melt pans or frying ranges, the use of a sprinkler system would be very hazardous to building occupants. Equally, the hazard might relate to damage to essential equipment, such as in a server room, where an alternative method of fire protection should be employed.

In such circumstances, the inability to safely install and use sprinklers should be mitigated in the protected building. Additional measures should be taken and may be in the form of alternative active fire protection measures, such as gaseous or water mist systems, or it may be that separation by fire-resisting construction would be more appropriate.

There are also areas of a building where, although it wouldn’t be potentially dangerous to install sprinkler heads, it might not be essential. Where there is no significant fire load, such as is likely in toilet areas, lifts, stairs etc., the area might be classed as a permitted exception. In such cases, a common fire protection measure is to ensure fire-resisting construction between the sprinkler-protected area and the non-sprinkler-protected area.

Permitted exception allowances vary depending upon the rules and standards in play. Under NFPA 13, such permitted exceptions may not be appropriate.

One additional measure that may be employed is cut-off sprinklers. These are sprinklers placed on the non-protected side, immediately above a window, doorway or other penetration of a compartment wall, and can sometimes be employed to improve the efficacy of the separation. Whether this is a measure worth taking should be considered in relation to the fire load present on the non-sprinklered side.

The LPC and NFPA rules both allow for circumstances where water curtains may be used for the protection of floor openings for escalators and open stairways.

In part 224 of LWF’s series on fire engineering we will look at hazard classification in relation to sprinkler systems. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.