From 2013 NFPA 13D all commentary
I would say you basically have a basement::
Residential sprinklers are generally not listed for use under exposed wood joists installed close together, which is a common ceiling configuration in an unfinished basement.
NFPA 13D requires these unfinished basements to be protected with sprinklers because such spaces are frequently used for storage or the installation of mechanical equipment, which can be an ignition source. Also, there is a possibility that basements or portions of them will be finished in the future and incorporate bedrooms, family rooms, or similar living and sleeping spaces. Subsection
8.2.4 provides guidance on how to provide sprinkler protection for these spaces in a reasonable manner, even though sprinklers are not specifically listed for use under exposed wood joists.
Residential sprinklers are not typically allowed for use under exposed wood joists, because the joists might delay the activation of the sprinklers and create a situation where the residential sprinklers do not activate in time to provide the necessary level of life safety. However, because the basement is unfinished, the probability is relatively low that someone is sleeping in the basement, and the greater level of sprinkler protection is not likely to be needed. It is expected that the residential sprinklers under the exposed wood joists would activate in a time sufficient to control the fire and allow occupants the time necessary to evacuate from other portions of the dwelling.
Where the basement is converted into a livable space where people could be sleeping, it is expected that the basement ceiling would be finished with sheetrock or tiles to cover the exposed wood joists. Having the sprinklers positioned in anticipation of a finished ceiling allows the basement to be converted without a sprinkler contractor having to come back and relocate the sprinklers. Of course, prudence needs to be exercised when installing the ceiling to make sure that the existing sprinklers are not damaged.
The requirement regarding the type of pipe in
8.2.4 ensures that this section is not used to violate the listing of special types of pipe material. Metallic pipe is not required to be protected, so it can be installed exposed below the joists. However, nonmetallic pipe is generally required to be protected (covered) unless its listing allows it to be installed exposed. So, in order to apply this provision with nonmetallic pipe, the provisions of the pipe’s listing need to be followed.
FAQ: Does the homeowner need to state an intention to finish the basement in order to use
8.2.4?
The assumption of
NFPA 13D is that the potential exists for all unfinished basements to someday be finished. Therefore, a homeowner is not required to specifically state that they are going to someday finish the basement in order to apply
8.2.4. When bidding and planning the sprinkler installation, the sprinkler contractor can assume that the basement will someday be finished and that a ceiling will someday be installed to cover the exposed joists.
8.2.4 Basements Without Ceilings.
In basements where ceilings are not required for the protection of piping or where metallic pipe is installed, residential sprinklers shall be permitted to be positioned in a manner that anticipates future installation of a finished ceiling.