Sprinkler Omission Requested for a Small Group C Office in a Combustible Building
A three-storey office building of 900 m² per floor is of combustible construction with a permitted area that is only adequate if the building is sprinklered. The owner wants to omit sprinklers on the third floor because it will be used only for storage of paper files and will be unoccupied most of the time. The building currently has a full sprinkler system designed to the applicable standard, and the third floor is within the same building. The designer is asked whether the third floor can be deleted from the sprinkler coverage while keeping the rest of the building sprinklered, and what effect that has on the building's compliance basis.
1. Can the third floor be removed from sprinkler coverage while the building relies on sprinklering for area and height compliance?
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No. The building's compliance with the allowable area and height provisions depends on the entire building being sprinklered. If the third floor is removed from coverage, the building is no longer a sprinklered building for the purpose of those provisions, and the permitted area and height must be re-evaluated without the sprinkler credit. For a combustible three-storey office of 900 m² per floor, the unsprinklered permitted area is likely to be exceeded, so the omission would render the building noncompliant. In addition, the third floor's storage of paper files is a higher fire load than an office, which increases the risk rather than justifying omission. The correct answer to the owner is that partial sprinklering that is relied upon for code compliance is not permitted; the system must protect the whole building, and any change in storage use should be assessed for sprinkler design density rather than removal of coverage.
2. If the owner insists on reducing sprinkler coverage, what alternative paths could the designer explore, and what are their trade-offs?
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The designer could explore three alternatives. First, retain full sprinkler coverage but adjust the third-floor design to a higher density appropriate for the file storage, which preserves the building's compliance basis and addresses the increased fire load. Second, if the owner truly wants no sprinklers on the third floor, the building would need to be reclassified as unsprinklered, which likely requires reducing the building area, adding fire separations, or changing construction to noncombustible to meet the unsprinklered permitted area; this is usually more expensive than sprinklering. Third, the third floor could be separated as a distinct building by a fire wall, but that only helps if the separated portion itself complies as an unsprinklered building, which it probably does not at 900 m² of combustible construction. The designer should present these options with cost implications and note that any change requires re-submission and approval, since the original permit was based on full sprinkler coverage.