The International Residential Code (IRC) is the predominant model residential code in the U.S. The IRC as a model code, requires sprinklers throughout one- and two-family homes and townhouses, however, several jurisdictions remove the fire sprinkler mandate. This short guide considers the mandate but accounts that jurisdictions do adopt the IRC without sprinklers in new construction.

This guide is useful to sprinklered and unsprinklered IRC users as it locates each fire sprinkler benefit in the IRC, summarizes the benefit, quotes the IRC section number (as it pertains to the 2021 edition) and identifies which edition of the IRC the benefit was first introduced into the code and remains in the IRC up to the 2021 edition.

IBC Occupancies in the IRC

• The following International Building Code (IBC) occupancies are permitted, by the IBC to be built to the IRC, when sprinklers are installed per P2904/NFPA 13D throughout:
  • Live/work units located in townhomes. 2
    • 2009 edition
  • Owner-occupied lodging with five or fewer guestrooms (IBC 310.4.2). R101.2
    • 2012 edition
  • A care facility with five or fewer persons receiving custodial care within a dwelling unit. (IBC 308.2.4 and 308.5.4)
    • 2012 edition
  • A care facility with five or fewer persons receiving medical care within a dwelling unit. (IBC 308.3.2)
    • 2012 edition
  • A care facility for five or fewer persons receiving care that are within a single-family dwelling. (IBC 310.4.1)
    • 2012 edition

Exterior Walls

• Exterior walls in homes with sprinklers can be built closer to lot line. Projections, openings in walls and penetrations into dwellings with sprinklers are permitted more than unsprinklered dwellings. Table R302.1(2)
• Residential subdivisions where all the dwellings are equipped throughout with an automatic sprinkler system the fire separation distance for exterior walls that are not fire-resistance rated and for fire-resistance-rated projections is permitted to be reduced to 0 feet, and unlimited unprotected openings and penetrations, where the adjoining lot provides an open setback yard that is 6 feet or more in width on the opposite side of the property line. Table R302.1(2)
  • 2009 edition

Townhouses

• The common wall between townhomes can be reduced from 2-hr to 1-hr fire-resistance rated wall where dwellings on both sides of the common wall are sprinklered per P2904/NFPA 13D. R302.2.2
  • 2015 edition
• Sprinklered townhouse units built to the IRC are not required to be structurally independent from one another. R302.2.6
  • 2021 edition

Two-Family Dwelling

• Dwelling unit separation wall can be reduced from 1-hr to 30 minutes where sprinklered per P2904. R302.3
  • 2021 edition

Through Penetrations

• Wet fire sprinkler piping is permitted as a through penetration where the annular space is filled with an approved material. R302.4.1
  • 2021 edition

Membrane Penetrations

• Wet fire sprinkler piping with metal escutcheons covering the annular space installed in fire-resistance rated walls or ceilings protect membrane penetrations. R302.4.2
  • 2021 edition

Fire Protection of Floors

• Fire sprinklers eliminate ½ inch gypsum or 5/8-inch wood panel on underside of floors. R302.13
  • 2012 edition

Residential Subdivisions

• Residential subdivisions where all homes are sprinklered can have nonrated exterior walls and unprotected openings/penetrations with a zero feet lot line. Adjoining lot line setback shall be six feet minimum. Table R302.1. (2) Footnote a
  • If attached garages have exterior walls adjacent to the lot line, garages shall have sprinklers. R309.5
    • 2009 edition

Emergency Escape Windows in Basements

• Fire sprinklers eliminate emergency escape and rescue openings in every basement sleeping rooms where one of the following are present: R310.1
  • One means of egress according to R311 and one emergency escape and rescue opening, or
  • Two means of egress according to R311.
    • 2018 edition

Photovoltaic Systems

• Provides alternative setback options for photovoltaic systems when an automatic sprinklers system is installed. PV systems are permitted to occupy 66% of the total roof area with only an 18” setback from the horizontal ridge, while increasing to a 36” setback when occupying more than 66%. The 36” setback is required at 33% coverage on a non-sprinkled dwelling. R324.6.2.1
  • 2018 edition

Mezzanines

• Open and unenclosed mezzanine area can be increased to one-half (an increase from one-third) of the floor area of the room of sprinklered dwellings. Cannot be combined with enclosed mezzanine exceptions in R325.5. R325.3
  • 2018 edition
• Mezzanines in buildings up to two stories, having two or more means of egress are not required to be open to the same room as the mezzanine where sprinklers are installed according to NFPA 13R and NFPA 13D. R325.5
  • 2015 edition

Habitable Attics

• A habitable attic is not considered a story above grade plane when it is not greater than 50% of the floor below when equipped with fire sprinklers. R326.3 Ex. 1.2
  • 2021 edition
• Sprinklers permit a habitable attic located above a third story on a dwelling unit and townhouse. R326.3 Ex. 4
  • 2021 edition

IRC sprinkler benefits in the IFC

• Fire flow (Appendix B of the IFC and needs to be specifically adopted by the jurisdiction)
  • Single-, two-family, townhouses, Group R-3 and Group R-4. IFC Table B105.1(1) 2015 edition
    • Sprinklered buildings of 0-3,600 sq. ft. have a min flow of 500 gpm for 30 minutes vs. unsprinklered of 1,000 gpm for 60 minutes
    • Sprinklered buildings 3,601 sq. ft. and greater have one-half the gpm (fire flow) for 60 minutes maximum.
• Fire hydrant spacing (Appendix C of the IFC and needs to be specifically adopted by the jurisdiction)
  • Fire hydrant spacing is increased for distance between hydrants and road frontage to hydrants by 25%. IFC Table C102.1 footnote g. 2015 edition
  • Fire apparatus access roads (Appendix D of the IFC and needs to be specifically adopted by the jurisdiction)
    • One- and two-family developments
      • Two separate fire apparatus access roads are required where there are more than 30 dwelling units, however where sprinklered to NFPA 13D, access from two directions is not required. IFC D107.1 2015 edition