The LWF Blog
Fire Safety Engineering for Design – Sprinkler Installation Planning – Part 247
August 11, 2025 10:29 amLWF’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 246, LWF discussed sprinkler installation design, including factors affecting design and the building’s construction features. In part 247, we talk about the spacing of sprinklers, including the maximum allowable distances between sprinkler heads.
When calculating the spacing between sprinklers in your installation, the area per sprinkler is calculated as the area between four adjacent sprinkler heads, regardless of the spacing method utilised (standard or staggered) for ordinary hazard risks.
The maximum allowable distances between sprinkler heads for standard installations (applicable to most countries, but it’s important to check local requirements) are as follows:
As per BS EN 12845 and figures are in metres:
Light hazard 4.6 (x 4.6 approx)
Ordinary hazard 4.0 ( x 3)
High hazard 3.7 (x2.4)
NFPA 13’s figures vary slightly from the British Standards for maximum allowable distance for sprinkler heads, as follows:
Light hazard 4.6
Ordinary hazard 4.6
High hazard 3.7
The NFPA code does allow some small concessions when protecting smaller rooms. A fire in a small room builds up heat very quickly and so the sprinkler heads are likely to operate earlier than it would in a large room. The spacing is therefore permitted to be wider in a small room than in a larger room. NFPA and Australian sprinkler codes allow special sprinklers to be used where appropriate provided the manufacturer’s guidance is adhered to.
Decisions made on the location of sprinklers will obviously be affected by spacing requirements, but should be made also considering their proximity to the ceiling in that they should be close and the sprinkler heads should not be obstructed by any building features or other services.
Sprinklers should be positioned above the risk and where they would be most effective once operational. The British Standards covering the design of atriums states heights of 7.5 m and 10 m, depending upon the response time of the sprinkler head to enable control of a design fire of 2.5 MW.
Atriums in buildings bring challenges to effective fire safety and fire protection. Ceiling heights are often too high to enable protection by sprinklers at that level and locating sprinklers at the edges of adjacent floors may have the undesirable effect of cutting off the atrium from the protected floor.
In part 248 of LWF’s series on fire engineering we will talk about drencher systems for glazing, and continue to discuss the suppression of fire in atriums. 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.