Building standards - Standard 2.15 Automatic Fire Suppression Systems: cost benefit analysis
We commissioned this cost benefit analysis research to inform the decision making process for Limitations to Standard 2.15 Automatic Fire Suppression Systems – Alterations, Extensions and Conversions , to consider the circumstances which would support the relaxation of the Standard to assist in the proposal to amend the limitations of Standard 2.15.
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6. Analysis of Costs
6.1.1 The costs reviewed in Section 4 tend to relate to new or retro-fit projects, rather than conversions, extensions or alterations to existing properties. As a result, discussions were held with a major supplier of fire suppression systems to gather costs to inform the analysis.
6.1.2 In considering the costs associated with installing a sprinkler system into conversions, alterations and extensions, it is assumed that these buildings do not have a sprinkler system already installed. Applications for a relaxation of Standard 2.15 are not anticipated for properties which already have a sprinkler system, as the cost of extending the system is unlikely to be prohibitive.
6.1.3 The previous studies identified the main costs of installing sprinkler systems as:
- Installation costs.
- Water supply costs.
- Annual maintenance costs/ongoing costs.
6.1.4 For non-sprinklered properties undergoing conversion, extension or alteration, there are a wide range of potential projects across the different building types. Section 3 highlighted that over 70% of conversion projects were to form a maisonette from either an attic space or two flats. A further 20% of conversion applications were to convert commercial property to form flats.
6.1.5 Given that previous studies have not examined conversion, extension or alteration projects, a few example projects were identified and cost estimates provided for the three components of cost listed above.
6.1.6 Four conversion projects relating to the provision of domestic residential accommodation and two extension projects for care homes were identified:
1. Conversion of two flats into a maisonette or an attic space above a flat to form a maisonette (e.g. 1-2 bed flat into 2 to 3 bed maisonette). Approx 70 sq. m. to 140 sq. m.
2. Conversion of a large flat or maisonette into two flats. This is the converse of 1 above to determine if the per unit cost would be less.
3. Conversion of commercial/public buildings (e.g. office/school) to residential flats on a small scale – less than 20 flats.
4. Conversion of commercial/public buildings (e.g. office/school) to residential flats on a large scale – more than 50 flats.
5. Extension of 4 rooms to a small 8-bed care home.
6. Extension of 10 rooms to a large 40 bed care home.
6.1.7 The following points should be noted about the cost information provided:
- All costs relate to BS 9251:2021 which came into effect on 30th June 2021. The latest version of the standard requires more monitoring and has wider implications for the coverage of the system than the previous version of the Standard. Hence, costs are higher than they would be for a system meeting the earlier version of the Standard (BS 9251:2014).
- BS 9251:2021 has four risk categories which have minimum design parameters which determine the number of heads that should be used to calculate the amount of water and pressure required to run the system. All costs in this analysis relate to Category 1 to Category 3 levels as appropriate:
- Category 1: covers individual dwellings and small blocks of flats and requires a minimum run time of 10 minutes with 1 or 2 heads included the calculation.
- Category 2: covers residential care homes with 10 or less residents. It requires a minimum run time of 30 minutes with 1 or 2 heads in the calculation.
- Category 3: covers larger residential care homes with more than 10 residents. It requires a minimum run time of 30 minutes with 2 or 4 heads in the calculation.
- None of the analysis is applicable to Category 4 systems which cover buildings over 18 metres in height and have greater run times and water supply requirements.
- The analysis has not considered the costs of installing a mist suppression system. The Standard for mist systems is older and not comparable to BS 9251:2021.
6.2 Costs of Sprinkler Systems
6.2.1 For the six project examples, the costs of installing the sprinkler system were provided. These costs exclude any other building costs and VAT but include a 2.5% main contractors discount. Table 6.1 provides a summary of the installation costs.
|Total Cost, £||Cost per Unit, £|
|Two flats or attic space into a maisonette||11,000||11,000|
|Maisonette into two flats||15,000||7,500|
|Commercial building into 20 flats||42,000||2,100|
|Commercial building into 50 flats||93,500||1,870|
|Small care home extension (4 rooms)||12,700||12,700|
|Large care home extension (10 rooms)||18,300||18,300|
Note: these costs assume the work is based in the central belt and where more than one flat is created, the protection is provided to the apartments only and not to any communal areas. For the care homes, protection is provided to the 4 or 10 additional rooms plus associated common access. A main contractors discount is included but the costs exclude VAT.
6.2.2 The installation costs associated with the formation of a maisonette are considerable at £11,000. The cost of converting a commercial building into flats is substantial, but when considered on a per unit basis, it falls considerably to around £2,000 per unit. The costs of installing a system into the care home extensions are also substantial.
6.2.3 Discussions with the system supplier suggested that there is a move towards pump and tank water supply to ensure that the required water pressure and flow for the system can be delivered. Table 6.2 provides summary of the costs associated with installing a pump and tank for each project type.
|Total Cost, £||Cost per Unit, £|
|Two flats or attic space into a maisonette||11,100||11,100|
|Maisonette into two flats||11,100||5,550|
|Commercial building into 20 flats||15,500||775|
|Commercial building into 50 flats||19,300||386|
|Small care home extension (4 rooms)||19,300||19,300|
|Large care home extension (10 rooms)||19,300||19,300|
Note: for the projects converting commercial premises to flats, the pump and tank are assumed to be located the building. Due to the small care home extension taking the number of residents to more than ten, it is assumed that the project may become a Category 3 project under BS9251:2021 which requires a larger capacity tank. If the project remains at Category 2 level, the tank size and cost could be reduced. A main contractors discount is included, but VAT is excluded.
6.2.4 If it is possible to use the mains water supply rather than a pump and tank system, the cost would fall to zero as a spur would be taken from the existing supply.
6.2.5 The annual cost of maintenance is advised to be £200 per unit.
6.2.6 Table 6.3 provides a summary of the total cost of installing a system per unit for both mains fed and pump and tank systems. The key points to note are:
- The costs are substantially lower for mains fed systems, particularly where a maisonette or one or two flats are created or a care home is extended.
- The costs reduce considerably with the number of units in the building project. Where there are only one of two properties associated with the conversion or extension, the cost per unit is very high. Where a larger number of units can be created, the costs per unit falls considerably, reflecting economies of scale in the installation process.
|Total Cost (Mains)||Total Cost (Pump & Tank)|
|Two flats or attic space into a maisonette||11,000||22,100|
|Maisonette into two flats||7,500||13,050|
|Commercial building into 20 flats||2,100||2,875|
|Commercial building into 50 flats||1,870||2,256|
|Small care home extension (4 rooms)||12,700||32,000|
|Large care home extension (10 rooms)||18,300||37,600|
Note: Costs exclude annual maintenance costs
6.3 Application of Costs to Building Types in Standard 2.15
6.3.1 Table 3.1 highlighted that the majority of applications for relaxations (to date) relate to conversions of either attic space or two flats to form a maisonette. Table 6.3 shows that regardless of the water system adopted, there are very considerable costs associated with the installation of a water suppression system into this type of conversion. The cost benefit analysis will be undertaken for the two maisonette conversions.
6.3.2 Table 3.1 also shows that there were four extension projects to ground floor flats, of between 14 and 35m2. It is very difficult to provide example costs for extension projects as the configuration of the system will depend on the size of the extension, the configuration of partitions and the use of the space. However, total costs in Table 6.3 are relatively high for the formation of a maisonette or one or two flats, particularly if a pump and tank are required. It is therefore expected that the costs would also be relatively high for an extension to an existing building for domestic residential purposes as the effects of economies of scale on unit cost are not likely to exist for an extension project. No specific extension project will be analysed in the cost benefit assessment, but broad conclusions will be drawn from the conversion results.
6.3.3 There have been no applications (to date) for a relaxation of the Standard for HMOs. It has not been possible to obtain costs for the conversion of a large property into a HMO, but the cost of installing a fire suppression system into this type of property is assumed to be similar to the costs of converting a maisonette into two flats. The cost benefit analysis will therefore adopt the maisonette to two flats costs when considering HMOs.
6.3.2 There have been no applications (to date) for a relaxation of the Standard for social housing. As stated previously, social housing is more a description of the ownership/occupiers of the dwelling than a building type per se. There is no reason to believe the costs of installing a fire suppression system into a building which would be used for social housing would be different to the costs of installing a system into a building to be used as mainstream housing. The cost benefit analysis will adopt the cost estimates in Table 6.3 for small and large commercial conversions to flats for the assessment of social housing.
6.3.4 There have been no applications (to date) for a relaxation of the Standard for care homes to date. The analysis will consider the costs of the two care home examples in Table 6.3.
6.3.5 There have been no applications (to date) for a relaxation of the Standard for sheltered housing. No specific costs were provided for sheltered housing projects, but the analysis will adopt the costs for conversion of commercial buildings into flats.
Retail – Enclosed Shopping Centres
6.3.6 There have been no applications (to date) for a relaxation of the Standard for enclosed shopping centres. As a project relating to an enclosed shopping centre would be a commercial project the fire suppression system would have to meet BS 12845:2021. This is a more onerous standard and the cost information obtained from the system supplier is not applicable to projects required to meet this standard. No specific cost benefit assessment will be undertaken for retail.
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