Sprinkler Age A Publication of the American Fire Sprinkler Association
Protection Requirements
Sprinkler protection in NFPA 13R, Standard for the Installation of Sprinkler Systems in Low-Rise Residential Occupancies, would appear to be straightforward, but with architects getting more creative with their designs, we are forced to seek assistance in navigating the nuances of the standard. The committee members have taken a big step in defining how to protect garages. This article will discuss the three possible design bases, but the main point is clarification that has been added in the 2019 edition. There are several factors that must be considered before being able to determine the proper protection scheme for garages. The most significant one is: are the garages accessible by just one tenant or are they publicly available to anyone who lives in the building? Most of the allowances we discuss here have been in the standard since the 2002 edition of NFPA 13R with some minor revisions along the way.
When it comes to garages that have to be sprinklered under the guidance of NFPA 13, Standard for the Installation of Sprinkler Systems, what are the driving factors that require a full-size system? Let’s start this discussion assuming a minimum remote area of 1,500 ft2. These garages will be accessed by more than one dwelling unit. These garages receive a higher level of protection by applying specific design parameters from NFPA 13. This is still an NFPA 13R system and the determination of what areas are to be protected is still defined by NFPA 13R. Sprinklers shall be spaced per ordinary hazard occupancies. There are a few things we need to look at, such as: can we use a wet system with quick response sprinklers for a remote area reduction per NFPA 13 section 11.2.3.2.3.1? While this is not explicitly stated, it is allowed provided we meet all five of the items listed. For example if the garage has a ceiling height of 10 ft that’s a 40 percent reduction in remote area size from 1,500 ft2 to 900 ft2. If our sprinklers are spaced at 125 ft2 per sprinkler, we have moved from discharging 12 sprinklers in our calculation to just eight sprinklers. That can be a huge benefit if water pressure is an issue or to prevent having to use larger sized pipes. Conversely, if the system must be a dry system, this drives our design area to 1,950 ft2. A question that occasionally comes up is: can we use a standard response sprinkler in lieu of a quick response sprinkler since we are designing to an ordinary hazard occupancy? The answer is “no” since NFPA 13R section 6.2.2.1 says sprinklers located outside the dwelling unit shall be quick response except as permitted by section 6.2.2.2. This section allows residential sprinklers to be installed outside the dwelling unit in eight different areas, one of which is inside garages per section 7.3.3.1(1). Currently, all information leads us to quick-response sprinklers. For 2019, though, a new section allows us to use standard response sprinklers when using NFPA 13 criteria. The committee statement was: “Currently all sprinklers outside the dwelling unit must be quick response or residential. In garages, many times it is difficult to route wet sprinkler piping to the limitations of a standard spray quick response sidewall sprinkler. In some configurations a dry system has to be installed. Allowing standard response sprinklers will give the user more options.”
Let’s now look at another possible option for areas outside the dwelling unit (garages). Section 7.2.3.1 allows us to use a “hybrid” room design method in compartments 500 ft2 or less. This is very much like a room design method from NFPA 13, only doors are not required to be rated and rated construction is only 30 minutes even for ordinary hazard occupancies. You are still limited by the size openings, but we can ignore the opening from the overhead door in that assessment. You must meet all of the five items listed. But the payoff is a maximum of four sprinklers. This option will not likely come into play very often since smaller garages will typically be serving only one dwelling unit (which allows the next option).
Let’s move on to garages protected by NFPA 13R with the lowest required system demand. If the garage is not an open space and is separated into individual garages serving a single dwelling unit, it can be protected per the requirements of section 7.3.3. It states: “ … shall be considered as part of that dwelling unit” (basically an extension of your living room). We can use either residential or quick-response sprinklers including quick-response extended-coverage sprinklers at a density of 0.05 gpm/ft2 per section 7.3.3.1 flowing no more than four sprinklers. Is this telling us that just because the unit serves only one unit, that the level of protection is equivalent to that typically required for a garage? Section A.7.3.3 explains that residential and quick response sprinklers discharging 0.05 gpm/ft2 have not been tested for use in garages, but field experience has shown they will activate and sound an alarm while discharging water assisting in controlling a fire. This philosophy was borrowed from NFPA 13D, Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes. This is an amazingly casual thought for the technical committee in this situation. The provisions of section 7.3.3.1(3) allows us to use a density less than light hazard occupancies, but if you do the math a 5.6K sprinkler operating at a minimum of 7 psi would be all but impossible to actually achieve the 0.05 gpm/ft2 density obvious answer is to use a smaller K-factor sprinkler to limit the over discharging in the garage. This raises the question when using spray sprinklers (since smaller K-factors can only be used in a light hazard occupancy) can it be applied in a garage (which is an ordinary hazard Group I)? The obvious answer is “yes,” but since the standard doesn’t explicitly say that be prepared to point out that the very low density confirms the intent is to allow smaller K-factors. Additionally, residential sprinklers can be used with no restrictions and most have a K-factor less than 5.6, so why would we limit the k-factor on one and not the other? The biggest issue that we’ve seen with this option is can it be applied to a private garage where the access door of the garage opens into a public corridor? This issue has been cleaned up in the 2019 edition. Previously, the typical interpretation (that we’ve always argued against) is that to apply this option, the garage had to be attached (share a common wall with a door into the garage) because section 7.3.3 states: “Garages that are accessible only from a single dwelling unit …” Now the committee revised the standard in the 2019 edition with a new section 7.3.3: “Garages that serve only a single dwelling unit shall be considered as part of that dwelling unit.” The old criteria was retained as section 7.3.4. While the wording is similar to the old criteria, its intent is for garages accessed by only one dwelling unit regardless of the separation. To confirm that, you can look at the 2019 edition section A.7.3.4 that states: “Garages serving a single dwelling unit include garages that are directly connected to the dwelling unit and garages that are served by a common corridor with access limited to a single owner or tenant.” The thought behind this is that the fire loading inside the garages are no different than if the garage was directly accessible from within the dwelling unit itself.
In closing, there are three options that can be applied to sprinkler protection in garages. It’s pretty black and white when and where the different options can be used. The primary driving variable, though, is whether or not the garage serving more than one dwelling unit.
ABOUT THE AUTHOR: Tom Noble, CET, CFPS, is technical programs specialist for AFSA. He has 23 years’ experience in the fire protection industry. Noble is tasked with writing AFSA’s informal interpretations on technical questions, as well as co-teaching AFSA’s Beginning Fire Sprinkler Planning School. Noble serves on the NFPA 13 Installation, NFPA 13D, and NFPA 13R committees, and is a member of NFPA’s Certified Water-Based Systems Professional (CWBSP) certification advisory group.
IMPORTANT NOTICE: The article and its content is not a Formal Interpretation issued pursuant to NFPA Regulations. Any opinion expressed is the personal opinion of the author and presenter and does not necessarily present the official position of the NFPA and its Technical Committee.
