Douglas Krantz - Technical Writer - Describing How It Works

Do we need horns and strobes in a building shell?

A building shell won't be used right away by anyone. However, because people can use the area without a building permit, so a building shell requires horns and strobes just like any other occupied area.

Do we need horns and strobes in a building shell?


You were such a help with the last question we asked. Thanks!

I have an architect who is questioning whether we need the strobes in a Building shell. I designed the Fire Alarm System showing Horn Strobes throughout and Strobes only in the bathrooms. I assumed that the building would be occupied at any given time as bathrooms are there. I would like to be a more informed designer. How would you look this up?

Reguards, N C

The fire alarm system is there to detect fire and warn people of the fire.

Shell Space Occupancy

Well, when designing a fire alarm system, the first thing is to know what kind of occupancy is going to be in the area with the fire alarm system. The occupancy types are determined in the International Building Code (IBC) or the NFPA101. Which set of codes or guidelines will be used is up to the government of the area. The type of fire alarm system used will be determined by how the area of the building is occupied.

A shell of a building implies that the owners don't really know what the occupancy is going to be, exactly, so whatever fire alarm system is installed has to take that unknown factor into consideration.

Lots Can Be Changed

Between the time that the shell is completed and the time the final occupants move in, a lot could change. If the shell space is originally designed for retail space, the final occupancy could be repurposed as a school, as an office, as a retail store, or even as storage or as a warehouse.

Basically, the repurposing of the shell space could involve lot of remodeling, a little remodeling, or no remodeling. If there's no remodeling, there won't have to be any need for a building permit so the fire alarm system will remain the same as it was installed in the first place.

Sometimes, when we design fire alarm systems and we don't know what the building is going to be used for, we have to add a lot of common sense.

Who Knows What the Shell Will Be Used For

Because no one knows what the shell is going to be used for, we have to understand what we are dealing with.
  • The shell has some sort of ventilation; the shell is designed so that people can be in the space.
  • The shell has bathrooms; the shell is designed so people can stay in the space for an extended time.
  • The shell could be used as a temporary warehouse; the shell could be occupied by people until a final repurposing and remodeling of the shell requires an upgraded fire alarm system.

Once the shell is finished and everyone walks away, the owner can, and probably will, use the space for other purposes until it is finally repurposed. Basically, the shell space is occupiable as it is and the whole fire alarm system should be designed as if the shell space will be occupied.

Sprinkler System

Common sense also says the shell space will be protected with a sprinkler system even though no one can think of anything that will be in the open space. This building-wide complete coverage sprinkler system is required because, in the future, someone may store something in the area without remodeling the shell space.

A complete fire alarm system, including proper warning devices (like horns and strobes), should be installed because, in the future, someone may occupy the area without remodeling the shell space.

Detect and Warn

The NFPA Code is interpreted differently by different people, but to be a complete fire alarm system, the system must detect fire (the waterflow switch on the sprinkler system) and warn people of the fire (horns and strobes). This detect and warn includes the shell area because the shell area can be occupied.

Douglas Krantz
Life Safety
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