Last edited 01 Feb 2018

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Business Sprinkler Alliance Institute / association Website

Case study A 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.

See also: Case study B for offices to show where automatic sprinklers have the greatest impact.


This case study illustrates the details contained herein for offices to show where automatic sprinklers are likely to have the greatest impact.

The example features a six-storey office building located in central London with 15,000m2 GIA and fully-glazed façades. The design guidance used is BS 9999 (no fire engineering) and the designs with and without automatic sprinklers are compared in terms of capital cost.

  • Offices 50x50 m2 .
  • 6 storeys – c. 24m.
  • Separation distances are; Northern side 20m, Eastern side 10m, Southern side 10m, Western side 5m.
  • Glazed façade.
  • 4 staircases.
Spinkler case study 1 image 3.jpg
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Spinkler case study 1 image 1.jpg

Firstly, the design impacts of incorporating an automatic sprinkler system on the fire protection measures are demonstrated in Table 6-2. Secondly, cost analysis of the impact is shown in Table 6-3.

[Table 6-2 Impact of sprinklers on the required fire protection measures for Building A]

BUILDING A Without Sprinklers With Sprinklers
Fire-rated façade area required

Northern side (17%) = 204 m2 Southern side (67%) = 804 m2

Eastern side (67%) = 804 m2

Western side (80%) = 960 m2

Northern side (0%) = 0 m2 Southern side (34%) = 408 m2

Eastern side (34%) = 408 m2

Western side (60%) = 720 m2

Stairs minimum width 1276 mm Stairs area 61.25m2 per floor 1120 mm Stairs area 53.75m2 per floor
Structural fire protection rating 90 minutes 60 minutes
Dry risers 3 2

[Table 6-3 Cost analysis of incorporating sprinklers in Building A]

BUILDING A Without Sprinklers With Sprinklers
Sprinklers installation cost £328,750
Façade cost13

Non FR façade= 2,028m2 x £600/m2 = £1,216,800

90min-FR façade= 2,772m2 x £2,200/m2 = £6,098,400

Total = £7,315,200

Non FR façade= 3,264m2 x £600/m2 = £1,958,400

60min-FR façade = 1,536m2 x £1,700/m2 = £2,611,200

Total = £4,569,600

Structural fire protection cost

90min-FR = 15,000m2 x £44.38/m2

= £665,700

60min-FR = 15,000m2 x £21.57/m2

= £323,550

Rental yields derived from changes to net internal area

45m2 x £650/m2/yr

= £29,250/yr

Dry risers costs

3 x £1,500/landing x 6 floors =

£27,000

2 x £1,500/landing x 6 floors =

£18,000

Total costs £8,007,900 £5,239,900 - £29,250/yr

Total cost impact of sprinklers

Capital cost impact = £2,768,000 saved by including sprinklers

Rental yield = £29,250/yr greater income by including sprinklers

Verdict: Installing automatic sprinklers in Building A can accumulate initial capital cost savings of c. £2.8M with an additional rentable area that can generate about £30k/yr. The additional rental income alone would pay for the automatic sprinkler system in 11 years. These values need to be used carefully however since there may be alternative measures that could be considered to reduce the cost of the façade such as an increase in compartmentation. This is particularly relevant here where the façade cost is high due to the need for fire-rated glazing. However, in this example automatic sprinklers have been shown that they can have a positive financial impact on a project.

Reference [13] Glazed fire-rated façade assumed required for aesthetic reasons by the client.

Read more: The impact of automatic sprinklers on building design.

--Business Sprinkler Alliance.

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