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

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).