It's a question that comes up again and again. Roughly 4 percent of new homes all over the country are being sprinklered, a figure that is on the rise. If the basements in these homes are “finished” - complete with gypsum board or acoustical tile ceilings - then certainly the type of sprinklers to be used in conjunction with this type of construction is listed residential pendent sprinklers or, more commonly, residential pendent “concealers.”
Meanwhile, if the basement is an “unfinished” basement, then you will logically want to turn to the code for answers. The trouble is, you won't find any.
First and foremost, the basement is considered part of the dwelling unit for any NFPA 13D installation. You must sprinkler the basement. Due in part to the omission of anything concrete relating to basements in 13D, there was a time when many contractors and “authorities having jurisdiction” (AHJs) alike thought that basements were actually exempt from the sprinkler requirement. In certain jurisdictions, single-family homes were sprinklered without any protection in the basement to speak of. It was the standard practice.
Thanks to that interpretation meltdown hundreds of homes today remain in that state of noncode compliance.
The source of much of the confusion can be traced to the code's basic intent. 13D emphasizes life safety over property protection. As a result, residential sprinklers are designed to provide homeowners 10 minutes to evacuate. The code's focus is on rooms in the home where people may congregate, sleep, eat or just relax. Not requiring sprinklers in small bathrooms and closets, for example, reduces the “level of protection” by a small percentage, but more importantly shifts the focus on properly designed coverage for areas such as the kitchen, living room and bedrooms.
This philosophy extends into the listing requirements for the residential heads. A residential sprinkler, which comes equipped with a “fast-response” thermal element, forms a “high-wall” uniform wetting pattern that consists of fine water droplets in a very flat spray. To be listed, quick-response sprinklers need not possess this “tenability” quality, and thus discharge water at a more direct angle in an “umbrella” pattern. The intent of the quick-response, standard spray sprinkler is to control a fire until the firefighters can arrive on the scene.
Section 7.5.1 of NFPA 13D states that listed residential sprinklers shall be used, except when dry pendent or dry sidewall sprinklers are extended into unheated areas - and inside mechanical closets, where quick-response heads are permissible for installation. Because of the way section 7.5.4 is worded, quick-response sprinklers are not to be used in any area of a 13D installation except for mechanical closets.
Code-Induced Coma: I happen to have a basement that is partially finished. In approximately half of my basement the ceiling consists of 2 x 10-inch wood joists spaced 16 inches on-center. Many new homes are built with completely unfinished basements, so how are engineers supposed to design the sprinkler piping?
The 13D code has only one thing to say about unfinished basements, and this is found in Section 8.2.5, which reads: “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.”
This tells us essentially nothing. The reason for the inclusion of this section is that, despite the fact that the term “residential upright sprinkler” is peppered throughout 13D, there exists:
• no known listed residential upright sprinklers anywhere in our galaxy, and;
• no residential sprinklers listed for the type of 2 x 10-inch wood joist construction mentioned above. Almost all residential sprinklers are listed for ceilings that are “flat, smooth and horizontal.”
So, let's move ahead to another deliberately loose section (8.2.3), which states, “sprinklers other than residential sprinklers shall be positioned in accordance with the positioning criteria specified by NFPA 13.” This definitely does not recommend or require compliance to NFPA 13 in its entirety. The subsequent section (8.2.4) notes that the positioning for these nonresidential sprinklers shall be such that response time and discharge are not unduly affected by obstructions such as beams.
Here's the kicker: The appendix for that section reads that “where obstructions occur, additional residential sprinklers are necessary to achieve proper response and distribution.” Again, the emphasis is on tenability and, please note, the authors of this code would be much more specific about unfinished basements if they considered them to be viable “living space” rooms where people might frequently gather.
What all of this rigmarole means is that what the code really wants the engineer to design and the contractor to install in an unfinished basement is exposed piping in the joist pocket, supplying a residential pendent with a deflector that hangs at least 1-inch below the bottom of the joist.
So that's fine and dandy - if the basement happens to be 10 or 12 feet high. But with most basement heights, it's only going to be a matter of time before some tall friend bonks his skull on one of these sprinklers. Then he's going to have a nice bump or laceration on his head and you might have a nice lawsuit on your hands. Oh, and don't forget - the installation of a headguard on that residential pendent sprinkler will violate its listing.
You're probably wondering why some sprinkler manufacturer just doesn't come out with a listed residential upright sprinkler. After all, it's obvious that the NFPA would heartily welcome that technological development. The answer is not so much a mystery as it is a stalemate.
The problem is the limited demand for those heads. Most homes being sprinklered at present are large and expensive ones, with finished basements. The number of more modest “unfinished basement” homes, in which sprinkler protection is required, does not represent a substantial market share.
Sprinkler manufacturers would love to market an upright residential sprinkler designed for use under smooth, flat ceilings because that would be an easy listing to obtain. However, things get tricky in terms of sprinkler response time when the ceiling is neither smooth nor flat. If a manufacturer does obtain a listing for such an upright sprinkler, the cost for the necessary approvals will run somewhere in the six figures. That's a big investment for such a small return.
So, it looks as though this situation is not going to be resolved in the near future. When it is, look for the first residential upright sprinkler that arrives on the market to run more than $50 each, since the manufacturer will have to cover all listing and testing expenditures.
Muddling Through: Although residential upright sprinklers are referenced throughout 13D, they are not produced by any manufacturer. This is what I strongly recommend for unfinished basements: Install either residential pendents (with a headguard - to heck with the listing), or standard spray uprights or sidewalls.
The option (see 22.214.171.124) to install standard upright heads on exposed piping must comply with the coverage criteria (spacing, positioning, etc.) in NFPA 13. This means that the maximum spacing coverage must be reduced to 130 sq. ft., and calculate to the densities noted in NFPA 13 (use 0.15 gpm/sq. ft.).The heads can be fast-response, but not (per 7.5.4) quick-response types. A.8.1.2 indicates that a system calculation for “beamed” ceilings “could require special design features such as larger flow, a design of three or more sprinklers to operate in the compartment, or both.”
The operative word being “could.” Once again the person performing the calculation is left with only vague direction. For instances like this, 13D also states that “guidance should be obtained from the manufacturer.” But to consult with an engineer representing the fire sprinkler manufacturer to determine the required flow demand for the calculations will only lead to more chatty discussions and no palpable instructions in writing. The wisest choice is to open three heads in the calculation and leave it at that.
This issue is a quagmire, and has caused all kinds of flagrantly misguided armchair interpretations from coast to coast. The nagging reality is that AHJs or consulting engineers must always seek to back up their reasoning with actual code documentation in spectacular black and white. In 13D, that's not available in consummate language.
I understand - the one thing we don't want to do in this business is to operate without guidelines. But before we get overly hung up on codes and listings, let's not lose sight of the fact that any residential basement sprinkler protection is a thousand times safer than the zillions of basements in this country without any whatsoever.
Nothing in the code firmly addresses required practice for sprinkler usage in unfinished basements. The code's primary premise is that the occupants have ample opportunity to escape. But bear in mind that if the basement is unfinished, the importance of this safety concept is, to a degree, diminished. Your best bet is to hope that the basement built for your project is 100 percent “finished.”