Case study B for offices to show where automatic sprinklers have the greatest impact

This article was originally published as part of The impact of automatic sprinklers on building design, an independent report produced by WSP, sponsored by the Business Sprinkler Alliance (BSA), published in September 2017.

This example features a four-storey office building located in Manchester with 1,600m2 GIA and fully-glazed facades. The separation distances around the building are:

Offices 20x20 m2.
4 storeys – c. 16m.
Separation distances are; Northern side 11m, Eastern side 20m, Southern side 12m, Western side 15m.
Glazed façade.
Occupancy capacity of the building.
2 staircases.

Firstly, the impacts of incorporating an automatic sprinkler system on the fire protection measures are demonstrated in Table 6-4. Secondly, cost analysis of the impacts is conducted in Table 6-5.

[Table 6-4 Impact of sprinklers on the required fire protection measures for Building B]

BUILDING B	Without Sprinklers	With Sprinklers
Fire-rated façade area required	Northern side (12.5%) = 40 m2 Southern side (0%) = 0 m2 Eastern side (0%) = 0 m2 Western side (0%) = 0 m2	Northern side (0%) = 0 m2 Southern side (0%) = 0 m2 Eastern side (0%) = 0 m2 Western side (0%) = 0 m2
Stairs minimum width	1000 mm Stairs area 24m2 per floor	1000 mm Stairs area 24m2 per floor
Structural fire protection rating	60 minutes	30 minutes
Dry risers	1	1

[Table 6-5 Cost analysis of incorporating sprinklers in Building B]

BUILDING B	Without Sprinklers	With Sprinklers
Sprinklers installation cost	£0	£97,600
Façade cost14	Non FR façade= 1,240m2 x £600/m2 = £744,000 60min-FR façade= 40m2 x £1,700/m2 = £68,000 Total = £812,000	Non FR façade= 1,280m2 x £600/m2 = £768,000 Total = £768,000
Structural fire protection cost	60min-FR = 1,600m2 x £21.57/m2 = £34,512	30min-FR = 1,600m2 x £12.38/m2 = £19,808
Rental yields derived from changes to net internal area	0 m2	0 m2
Dry risers costs	1 x £1,500/landing x 4 floors = £6,000	1 x £1,500/landing x 4 floors = £6,000
Total costs	£852,512	£891,408
Total cost impact of sprinklers	Capital cost impact = £38,896 added to the project cost plan by including sprinklers

Verdict: Installing automatic sprinklers in Building B is shown to add cost to the project and would not be recommended when reviewed against the impacts (cost, aesthetics etc.) reviewed herein. Unless there is another requirement requiring their inclusion (business continuity, property protection).

Reference [14] Glazed fire rated façade assumed required for aesthetic reasons by the client.

--Business Sprinkler Alliance