Fire Sprinkler Requirements

When do you need to sprinkle?

There has always been a level of confusion when it comes to plan review and what type of sprinkler system to provide in a particular structure or even within a particular use.  Massachusetts makes this a bit more confusing with its amendments and MGLs. Here is a walk through of the sprinkler system types, requirements, and exceptions under the code. This info will not cover every and all of the requirements, but it will present the core of what is required.

First, we must understand that we have a couple of documents to guide us as well as trigger the requirement for installation of fire sprinkler systems. The International Building Code , in Massachusetts the base code amendments, and NFPA 13: Standard for Installation of Sprinkler systems. 

Think of it this way:

The building code tells you what is required 


NFPA 13 tells you how to do it.

There are five primary locations within the current edition of the International Building Code (2015) that dictate triggers and requirements.  

  1. IBC Chapter 4 Special Detailed Requirements Based on Use and Occupancy gives us requirements for structures such as high rises, mall buildings and hazardous storage. 
  2. IBC Chapter 9 Fire Protections Systems is where you will find all the thresholds for sprinkler installation based on the size of the structure as well as the use and occupancy.  
  3. Here in Massachusetts, we also need to look at Chapter 9 of the Massachusetts IBC amendments, which has a significant number of amendments.  
  4. We also find sprinkler requirements in IBC chapter 5 General Building Height and Area. 
  5. Last but not least, Mass General Laws contain a number of modifications or amendments to the national sprinkler thresholds.

Types of systems

There are three types of sprinkler systems that we will consider: NFPA 13D, NFPA 13R, and NFPA 13.  Here are the primary differences for discerning one system from the other.

  • NFPA 13R and 13D systems are life safety systems only. They provide sprinkler coverage to assist in safe egress. These not considered to be fully sprinklered structures.
  • NFPA 13 is a system designed to protect life and property. They will allow for safe egress in addition to being designed to protect and save the structure.

Where can each system be used (generally)?

NFPA 13D can generally be used in one and two family dwellings under four stories. (Hold that thought.) Massachusetts has an amended allowance for the use of 13D in three family dwellings and townhouses under four stories and no more than 12,000 SF in total area.  (The code defines a townhouse as three or more attached.) 

This system can be served by a tank(s), domestic water supply, or a dedicated fire service line.

NFPA 13R serves residential building up to four stories in height with the highest occupied floor no higher than 60 feet. This requires a dedicated fire service line. 

NFPA 13 is allowed in all occupancies. It requires a dedicated fire service, and the building is considered fully sprinklered.

Now, we go into the weeds.

A  lot of confusion exists with the application of sprinkler requirements in one and two family dwellings as well as townhouses. This will help us segue into IBC Chapter 5 General Height and Area thresholds for sprinkler requirements.

The IRC and MA amendments pertain to one and two family dwellings as well as townhouses under four stories. Once you go above four stories you switch to the IBC for design and construction of these types of structures. Townhouses under four stories can be designed as single-family dwellings regardless of how many units area attached. It is the fire protection that changes based on the number and size of units. In townhouses with three units up to 12,000 SF of total area you can utilize a 13D in each individual unit or one system for all three units. If you were to exceed either three townhouse units, three stories (type five wood), or the 12,000 SF of area threshold then you will need a 13R system. 

Now, single family and two family dwellings….Chapter 5 General Height and Area dictates how many stories can be built in a structure based on the use and type of construction. A standard wood frame single family is allowed to be three stories in height. The only way to get to a fourthstory is by adding a sprinkler. You are not allowed additional stories with a 13D. You must utilize a 13R to gain additional stories. The same holds true for townhouse units.  

Significant Amendments and MGLs

As cited above, IBC MA Amendments allow buildings of three residential units or less under four stories to utilize a 13D system.

All townhouses with three or more must be sprinklered, regardless of fire separation.

Townhouses under three stories, regardless of how many are attached, can be constructed utilizing the IRC. However, the sprinkler requirements will be dictated by the IBC and MA Amendments to the IBC.

Nationally a B-Business Occupancy is allowed to go up to 12,000 SF before a sprinkler system is required. M.G.L. c. 148, § 26G drops that number to 7500 SF before sprinkler coverage is required.

Author: Michael Yanovitch

Building Department Manager, Code inspector, Plan Reviewer, Land Use Consultant, Hockey coach and most important of all... Dad

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