You asked the following questions: “A new is building being built that is adjacent to an existing building. The existing building has a wet sprinkler system and the new building will have a wet sprinkler system with a separate riser. Both risers feed off the same looped fire line that circles the property. The AHJ wants to consider it one structure since the buildings are adjacent. The issues in question are: 1) Is there anything in NFPA 13 that restricts a building to having only one riser or that states that multiple systems must be fed from the same riser? 2) Does the water supply have to be sized to account for two remote areas discharging simultaneously?” In response to your questions we have reviewed NFPA 13, 1999 edition that you
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The floor area for a single riser is limited to 52,000 sq. ft. for light or ordinary hazard occupancies and 40,000 sq. ft. for extra hazard and storage occupancies. The standard does not have a restriction on the number of risers that can be located in a building. The design approach is left to the discretion of the designer. They can select a single feed into the building with a manifold arrangement as a supply for multiple risers or each riser can have its own separate feed. The systems are designed for a single fire originating within the building. This concept was well understood by the industry until it was brought into question and included into the standard starting for the 2010 edition. The commentary regarding this issue from the 2013 edition Handbook states, “Prior to the 2010 edition, this standard was silent on the issue of multiple ignition sources because a single ignition scenario was assumed but not stated. The lack of such a statement led to increasing discussion and varying interpretation of the standard with regard to multiple ignition sources. One side of the discussion maintains that multiple ignition source fires, if not accounted for in the system design, could overwhelm the sprinkler system water supply. However, adding such a statement within the standard would still leave unresolved the determination of how many ignition sources should be considered and their appropriate location within the building. Attempting to resolve such wide-ranging variables would result in an overdesign of the system at considerable expense, with little technical justification. Therefore, the addition of 1.1.2 in the 2010 edition, now 1.1.3, clarified that the intent of the standard is to only consider a single ignition source fire for sprinkler system design. The volume of the
The floor area for a single riser is limited to 52,000 sq. ft. for light or ordinary hazard occupancies and 40,000 sq. ft. for extra hazard and storage occupancies. The standard does not have a restriction on the number of risers that can be located in a building. The design approach is left to the discretion of the designer. They can select a single feed into the building with a manifold arrangement as a supply for multiple risers or each riser can have its own separate feed. The systems are designed for a single fire originating within the building. This concept was well understood by the industry until it was brought into question and included into the standard starting for the 2010 edition. The commentary regarding this issue from the 2013 edition Handbook states, “Prior to the 2010 edition, this standard was silent on the issue of multiple ignition sources because a single ignition scenario was assumed but not stated. The lack of such a statement led to increasing discussion and varying interpretation of the standard with regard to multiple ignition sources. One side of the discussion maintains that multiple ignition source fires, if not accounted for in the system design, could overwhelm the sprinkler system water supply. However, adding such a statement within the standard would still leave unresolved the determination of how many ignition sources should be considered and their appropriate location within the building. Attempting to resolve such wide-ranging variables would result in an overdesign of the system at considerable expense, with little technical justification. Therefore, the addition of 1.1.2 in the 2010 edition, now 1.1.3, clarified that the intent of the standard is to only consider a single ignition source fire for sprinkler system design. The volume of the