Shadow Area

[jjmoore73]

Attached is an apartment in a multi-family project. We have completed 100+ of these 2 story buildings over the years and this problem came up once 6 years ago and was resolved with the AHJ. It has not been a problem until this week when a sr. inspector said we needed to add a sprinkler head at the entry location. I do not know the details of the original agreement, and I cannot find a specific code to eliminate the sprinkler head. Each building has 16 - 24 units, right now it is the small 2 bedroom unit with the 29" soffit over the entry in question. Some units have a 6" soffit and other units have an 18" soffit. Is the 6" soffit ok? What about 12"? When does it become a problem? The only code I could think of to counter act was the shadow rule. Does anyone have any suggestions?

Adding 1 head does not seem like a big deal, but it will be almost one hundred heads on buildings in various stages of construction and many already have sheetrock installed, but not yet painted. Getting pipe to the sprinkler head is another challenge.

 

[cdafd]

13 or 13R system?

 

[cdafd]

Sorry I see 13R

 

[cdafd]

Appears you are hitting the floor area and providing for exiting.

I do not see a problem.

Can you pull the head that is five feet back farther back,so you get just a little more coverage?

Not near 13r book right now [pre][/pre]

 

[stookeyfpe]

As a AHJ I would accept your design. It meets the requirements of 2013 NFPA 13R Section 6.4.6.3.3. Secondly the fire loss data in Annex Table A.1.2 substantiate that fires originating at an entranceway only contributed to 0.3% of the total Civilian deaths in the 4 years period of fire loss history for Apartments. Fires originating at the dwelling/sleeping unit entrance that result in the death or injury of Civilians are pretty miniscule when you look at the data in comparison to other areas of fire origin in Apartments.

 

[MatthewJWillis]

We must remember that a sprinkler is not just for wetting the floor. It is designed to cool the gases gathering at the ceiling. This is more critical with residential sprinklers and the required wetting of within 4" of where the gases gather.
Also, the fire rated construction of these type units actually diminish the time to flashover.

The shadow is for floor area, not at the ceiling.
Having said that, I do not see much of a problem in that people typically do not block the door with stuff, except hoarders.

I agree with pulling the sprinkler back and decreasing the angle...


Oh BTW,

Annex Table A.1.2 tells me that people have died from entranceway fires... Just a thought...


R/
Matt

 

[jjmoore73]

Thank you for the comments. I agree that we are getting floor coverage based on the angle shown. Ceiling coverage and high wall area near the ceiling does not have coverage. Before I consult with the AHJ, I wanted to see if there was an actual code that might help convince my case. Shadow area is for floor space, if there is no other code should I base my argument on that premise? I could move the head about 6" back. Design is based on 16x16 and I am about 7'6 away from the back wall near the door... Again, thank you for the ideas.

 

[stookeyfpe]

It's 9 square feet of area which rarely has any fuel package of any size to contribute to a fire's growth. NFPA 13R doesn't require sprinkler protection in a 24 square foot closet provided its walls and ceiling are noncombustible or limited combustible materials. If this building is built in the US and is subject to the IBC, the whole room is constructed with noncombustible or limited combustible construction because gypsum wall board is the predominant wall covering (at least in my jurisdiction, which serves about 740K people).

Going back to the Annex, and speaking strictly to areas of origin, 2,120 fires occurred in a 4 year period in closets versus 520 at lobbies or entranceways. You've exceeded NFPA 13R because if I am looking at your plans correctly, you have a sprinkler immediately outside the front door.

You're in compliance IMHO.

 

[MatthewJWillis]

Let's ask the question..,
Where does it say in 13R that one is required in the soffit? Your sprinkler should meet the obstruction guidelines, nothing more.
13R is meant to do one thing, get people out. If they are able to get out, and the building goes to the ground, we win.

For some clarification ammo, look at the requirements in 13 for stairs. For some reason, it is believed that the sprinkler should be located above the door. Per code, it is required to be under the first landing which is where storage can/will occur. It is not designed to protect egress.

Ask for code reference.

R/
Matt

 

[cdafd]

also from NFPA 13 R 2013 and also in previous editions

6.4.6.3.6.3 Sprinklers shall be positioned with respect to an obstruction against a wall in accordance with Figure 6.4.6.3.6.3.

 

[jjmoore73]

I like Stookey's optimism and common sense. We need some more of that in our jurisdiction.
CDA... This is the code that concerns me most. I don't know how to bypass it. Per Figure 6.4.6.3.6.3 we are not in compliance. 6.4.6.3.3.3 is a newer code regarding architectural features not exceeding 18 sq.ft. or more then 2' deep. I could meet the requirements except my area is 5" too deep. (6.2.3.5.2 in 2010 edition)

 

[TravisMack]

I think it is reasonable to assume that you have adequate protection for an NFPA 13R system. However, it seems that by the letter of the standard, a sprinkler is required at the ceiling in question. 6.4.3.6.3 is one area to hang on if you can meet compliance. However, being 10' above the lower soffit, you won't be able to throw under it. Then, you have to go to the solid obstruction criteria ( commonly called beam rule) if you can't comply with the soffit rule. You aren't in compliance with this either. So, that small space would need a sprinkler per the exact letter of the standard.

I'm not sure how you could get down to that sprinkler location without the pipe being in a place that could potentially freeze.

I wish I had a better response for you.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[cdafd]

nfpa 13 r 2013 edition

more argue:


6.4.6.3.1* Except as otherwise permitted in 6.4.6.3, residential sprinklers shall provide complete coverage of the floor area within the compartments requiring sprinkler protection.




A.6.4.6.3.1 Modern multiple-family building floor plans incorporate certain architectural characteristics or features that can initially seem to make absolute coverage of every single square foot of floor area a challenge. These features include angled walls, wing walls, slightly indented walls, and various soffit configurations.
The “problem” arises when one erroneously considers water discharging from a residential sprinkler to travel only in an absolute straight line, as if it were beams of light. When this approach is taken, small [1 ft2 to 3 ft2 (0.09 m2 to 0.28 m2)] typically triangular “shadowed areas” can in theory be formed on the floor adjacent to their referenced architectural features. The shadowed areas are purely on paper and do not take into account the dynamic variables affecting sprinkler discharge and distribution. It is hardly conceivable that anything located within one of these areas could remain dry during adjacent sprinkler discharge. The committee recognizes that such small theoretically shadowed floor areas are not an issue. Residential sprinkler distribution patterns are specifically intended to provide superior wall-wetting capability. Survivability of the occupants is more dependent on such wall-wetting than on absolute floor coverage.
Though not specifically referenced as such, in fact, NFPA 13 already permits an appreciable amount of “shadowing” by way of the basic obstruction figures and tables for various sprinkler applications. Take, for example, Figure 8.10.6.2.1.3 of NFPA 13, Minimum Distance from Obstruction (residential upright and pendent spray sprinklers). Consider a residential sprinkler spaced 10 ft (3.05 m) off of wall. A 12 in. (305 mm) round column located in the direction of the wall and 4 ft (1.22 m) away from the sprinkler would create an allowable “shadowed” area of approximately 8.6 ft2 (0.8 m2), using the line-of-sight approach.
The intent of NFPA 13R is to provide economically viable, flashover-preventing, survivability-enhancing residential sprinkler layouts. It is not the intent of NFPA 13R to require additional sprinklers for these 1 ft2 to 3 ft2 (0.09 m2 to 0.28 m2) areas.

 

[jjmoore73]

Thanks CDA.... I keep coming back to this one myself only to look for another direction because they are talking about floor coverage. The shadow effect, in my opinion, seems to be the strongest defense, but as Travis said, the exact letter of the standard indicates a head is required. Thank you for everyone's input.