(This discussion is based on the laws of the Commonwealth of Massachusetts,
but applies to most other parts of the country as well. Please check the
code(s) in effect your region before relying on or using this information).
SPRINKLERS SYSTEMS FOR RESIDENTIAL BUILDINGS
Whether or not a sprinkler system is required is usually determined early in
the design of a building. A code book is opened, an architect or engineer
flips to the appropriate chapter, and a decision is made. Sprinklers are required because of the nature of the occupancy, the size of the
building, the number of people expected to occupy it, and/or for other
reasons. The determination is usually straightforward.
Another one of the first steps in the design of a building is
determining how large it will be. Based on the type of construction and
the use group (i.e. occupancy) classification, limits for the maximum allowable area and
height are provided in a table in the building code. For the
most part, stronger, more fire-resistant structures and use groups with lesser
potential for loss of life are allowed to be built larger and taller.
For most use groups, the maximum area and height are allowed to be increased if certain other "features" are incorporated
into the design of the building. One such adjustment has to do with whether or not the building has an automatic
If you are an architect, or you hire architects to do work for
you, chances are you've utilized sprinkler systems so that you can make your
buildings larger and taller. In our experience, the biggest mistake that architects make is
assuming that all sprinkler systems are created equal.
essentially two types of sprinkler systems - residential systems, and non-residential
systems. The building code allows residential systems to be used in
residential buildings if certain criteria are met. The most important
point of this discussion is to emphasize the fact that BUILDINGS CANNOT BE MADE LARGER (I.E.
AREAS CANNOT BE INCREASED BEYOND THE LIMITS IN THE AFOREMENTIONED TABLES) WHEN A RESIDENTIAL
SPRINKLER SYSTEM IS UTILIZED. The building code is very clear on this point, yet it is
very often overlooked.
For the purposes of this discussion, residential
sprinkler systems are those that are designed in
accordance with NFPA 13R, "Standard for the Installation of Sprinkler
Systems in Residential Occupancies up to and Including Four Stories in Height".
What you may or may not realize is that there are important differences between
systems that are designed in accordance with NFPA 13R and those that are designed in
accordance with NFPA 13 (less the "R"), "Standard for the
Installation of Sprinkler Systems". NFPA 13 (less the
"R") covers the installation of
sprinkler systems in MOST types of buildings. NFPA 13R covers the installation
of sprinkler systems ONLY in residential buildings up to and including four stories
NFPA 13R was introduced in 1989 in an attempt to provide an
economical solution to the growing problem of fire-related deaths in the
home. NFPA 13R
systems are aimed more at saving lives than protecting property.
Although NFPA 13R systems
inherently provide a certain level of property protection, they are not intended
to save the building. They are intended to allow occupants sufficient time
The biggest advantage of NFPA 13R is that it allows a weaker
water supply. In many cases where an NFPA 13 (less
the "R") system would require a strong city water supply or an
expensive fire pump, an NFPA 13R system is achievable without either. NFPA
13R also allows the omission of sprinklers from attics and certain bathrooms and
closets. Fewer sprinklers means lower cost, and
attics in particular can get very expensive to protect because special measures
need to be taken to prevent water-filled piping from freezing. The
omission of sprinklers from these areas acknowledges statistics that show a low
loss of life in situations where fires start there. That's
not to say that fires don't start in these areas - indeed they do. And
without sprinklers, fires that start in these areas can grow and cause major
and/or complete destruction.
If you take one thing away from this article, let it be this -
you need to know what TYPE of sprinkler system is being installed in your
building. If you are building a residential building, you very well may be
given (or desire) an NFPA 13R system. If the system is to be designed in
accordance with NFPA 13 (less the "R"), then you needn't be so concerned
about the "increases" or building code "exceptions" you or your
architect are taking. Don't get caught making your building larger
with an NFPA 13R system though. We all know it is much more expensive to go back
and fix problems later.
An important fact to note is that under some circumstances, a
residential building CAN be made one story higher when a NFPA 13R system is
utilized (at least in Massachusetts). There are specific requirements and
it is important to be aware of and understand these requirements. Again,
in NO circumstance can the area of a building be increased when an NFPA 13R
system is utilized.
The effect of using an NFPA 13R system goes beyond the size of the
building. While this article will not cover the additional implications in
detail, it will mention a few topics that professionals in the State of
Massachusetts should note for further review. This list identifies some,
but not all requirements that are "relaxed" when you utilize an NFPA
13 system, but not if you utilize an NFPA 13R system. These include:
* No reduction in required separation
between use groups
* No decrease in fire resistance
rating of non-loading bearing exterior walls and no increase in
maximum area of exterior wall openings
* No omission of fire dampers where
ducts pass through one-hour fire rated walls
* No reduction in dwelling unit
separations (unless sprinklers are installed in all closets that border tenant
separation walls AND in all bathrooms)
* No relaxation of requirements for
accessible means of egress components such as exterior stairs and elevators
* Special auto-unlocking of doors in
means of egress not allowed (i.e. all egress doors must remain unlocked at all
This list should not be considered exhaustive, but rather as
an indicator that there are several areas where the use of an NFPA 13R system
may create issues.
Should you have any additional questions regarding residential
sprinkler systems please contact us. We can provide substantiation for the
statements made in the previous paragraphs
by providing excerpts from the Massachusetts Building Code.