In this column, I will reprise the column which appeared in the July 2009 edition of Plumbing Engineer, updated to current codes.

At the start of a design of a building, the plumbing engineer may receive a call from the architect asking this very question. Since the plumbing engineer is responsible for the design of the fire sprinkler system, the architect may presume that he or she should be able to answer this question easily. It is not always the case as the decision to provide sprinklers for a building can be based on factors beyond the control of the plumbing engineer. 

Let us assume the jurisdiction is using the 2018 edition of the International Building Code (IBC) and the 2018 International Fire Code (IFC). Let us also assume that the local jurisdiction has not made any amendments to these codes affecting sprinkler requirements. 

This column will attempt to outline many (but not all) areas in the codes where sprinklers are required or used to take advantage of the many trade-offs giving architects and builders flexibility and possibly cost savings in the design and construction of a building. Armed with this information, the plumbing engineer can be ready to assist the architect in answering this question. 

The plumbing engineer should be familiar with IBC Chapter 9, dealing with fire protection systems. In this chapter, Section 903.2 identifies several instances where sprinklers must be provided. The sprinkler requirements in this section are based on occupancy. In the case of high-hazard (Group H), institutional (Group I) and residential (Group R) occupancies, sprinklers are required across the board, although there are some exceptions. 

Regarding R occupancies, in many jurisdictions, one- and two-family dwellings do not fall under the building code but rather are covered by a separate residential or housing codes. The plumbing engineer will need to check those codes to determine if sprinklers are required. Again, be aware of any local amendments, as many jurisdictions are removing mandatory sprinkler requirements from their residential codes.

For other occupancies, Section 903.2 requires sprinklers when the building exceeds a certain floor area or when some special condition exists. For example, a retail store (Group M occupancy) with a fire area over 12,000 sq. ft. will require sprinklers.

When reading code language, read every word. When required, sprinklers are typically required “throughout the building.” However, there are instances where that is not the case. For example, Section 903.2.1 and its subparagraphs dealing with various Group A occupancies only require sprinklers “throughout all stories from the occupancy to and including the levels of exit discharge serving that occupancy.” It is also the case for stories or basements without openings (IBC Section 903.2.11.1). 

IBC Table 903.2.11.6, Additional Required Suppression Systems, similarly identifies other areas of the IBC where sprinklers will be required. Several items in this table are from IBC Chapter 4, including requirements for covered-mall buildings, high-rise buildings, buildings with atriums, underground buildings, hospitals, stages, special amusement buildings and aircraft hangers. The last row of the table reminds one to check Section 903.2.11.6 of the International Fire Code (IFC).

Beyond Chapter 9

IBC Chapter 9 does not provide all the answers to the question of whether sprinklers are needed in a building. A requirement for sprinklers can result from the type of construction selected for a given occupancy; it’s the number of stories or building area. Before the 2015 edition of the IBC, an increase in the basic allowable floor area of 200 percent for multistory buildings and 300 percent for single-story buildings was granted for sprinklers for most situations. One then had to calculate the total permitted area per floor and the building. 

The same allowances are still permitted but one no longer has to do the math. All the information is consolidated into Table 506.2, Allowable Area Factor. The table lists allowable areas per floor for the nonsprinklered condition, sprinklered one-story buildings and sprinklered multiple-story buildings. One can opt for sprinklers to get a larger building without an upgrade in the type of construction. 

Note that the value from this area can be further increased by the frontage allowance permitted by Section 506.3. The total area for the building can then be determined by applying the equations from Section 506.2. From the table, you can see no increases are allowed when NFPA 13R sprinkler systems are used in residential occupancies.

One can also use a standard NFPA 13 sprinkler system to add one story in height to the building and increase the maximum allowed height by 20 ft. using the requirements in IBC Table 504.3, Allowable Building Height and Table 504.4, Allowable Number of Stories. This provision can be taken advantage in addition to the area increases.

Please be reminded that when working with any tables, always check the footnotes.

Once used by the UBC and IBC as another sprinkler trade-off, the fire-resistive substitution was deleted starting with the 2015 IBC. It allowed for sprinklers to be “substituted” for the one-hour fire-resistance ratings required for Type IIA, Type IIIA or Type VA buildings. 

If one used the fire-resistance substation, it could not be used to substitute for exterior wall fire resistance or if sprinklers are required by other provisions of the IBC, such as to obtain an area increase or an increase in building height. According to the ICC publication, Significant Changes to the IBC 2015 Edition, the fire-resistance substitution was deleted “based upon its extremely limited applicability … along with the significant potential for misuse.” (And I might add confusion).

Sprinklers in combination with large open yard spaces around the building can also play a role in allowing certain occupancies in unprotected (i.e., no fire-resistance requirements) noncombustible or combustible construction to be of unlimited areas under the provisions of IBC Section 507. 

Reducing Requirements

The use of sprinklers can help with requirements for the protection of openings in exterior walls. IBC Table 705.8 limits the number of openings in exterior walls based on whether the opening is unprotected-nonsprinklered, unprotected-sprinklered or protected and the fire separation distance. 

In this case, the term “protected” means the opening has an opening protective assembly, such as a fire door or window or fire-rated glazing. As can be seen from the table, the unprotected-sprinklered condition has the same allowances as the protected condition, except, however, for Group H-1, H-2 and H-3 occupancies where the unprotected-sprinkler condition cannot be used.

Chapter 8, Table 803.13 shows a reduction in interior finish requirements when the building is sprinklered. Typically, a reduction of one class level is allowed. This chapter includes a requirement for sprinklers under certain conditions when textile wall coverings, expanded vinyl wall coverings and expanded vinyl ceiling coverings are used for interior finish. Section 804.4.2 permits a reduction in requirements for interior floor finish when sprinklers are provided.

IBC Chapter 10 on means of egress provides several areas where sprinklers can be used to reduce requirements, including: 

• For other than Group H and I-2 occupancies egress capacities are increased (Section 1005.3).

• Increased travel distances within the exit access to an exit for certain occupancies (IBC Table 1017.2).

• Corridor fire-resistance rating is reduced or eliminated for certain occupancies (IBC Table 1020.1).

• Dead ends for most occupancies are increased from 20 ft. to 50 ft. (IBC Section 1020.4, Exception 2).

• Common path of travel in certain occupancies may be increased (IBC Table 1006.2.1).

• Remoteness of exits. The separation of exits is reduced from 1/2 the diagonal to 1/3 the diagonal (IBC 1007.1.1, exception 2).

• Except for R-3 occupancies, emergency escape and rescue openings are not required for Group R-1 and R-2 occupancies (IBC Section 1030.1, exception 4).

If the IFC applies in your jurisdiction, there are several situations where this code may establish a requirement for sprinklers or make the addition of sprinklers desirable.

In IFC Section 503.1.1, which pertains to fire apparatus access to buildings, the fire chief is allowed to grant an exception to the 150 ft. requirement if sprinklers are provided. 

In IFC Section 508.5.1, exception 2 allows the distance requirement for a fire hydrant on a fire apparatus access road to increase from 400 ft. to 600 ft. if sprinklers are provided.

If the fire flow requirements of IFC Appendix B apply to your jurisdiction, IBC Section B105.1 allows an exception to reduce the fire floor requirement for one- and two-family dwellings by 50 percent if the building is fully sprinklered. Section B105.2 allows a reduction of up to 75 percent but not less than a minimum fire flow of 1,500 gal./minute, in the case of buildings other than one- and two- family dwellings.

In the case of high-piled combustible storage, IFC Table 3206.2 provides information as to when sprinkler protection is required.

This column identifies many of the sprinkler-related code provisions based on the IBC and IFC model codes. As is always the case, the engineer must check for variations in the codes adopted in the jurisdiction to ensure that a given item is still applicable. And remember, do not forget to read the footnotes.

By becoming familiar with the provisions of the IBC and IFC pertaining to sprinklers, not only those in IBC Chapter 9, the plumbing engineer can help the architect answer the question, “Are sprinklers required?”