Revisiting that sloped roof vs distances between heads issue

[ContractorDave]

One of the inspections I do is a school with an interesting architectural feature: the library is a tee-pee like affair, an 8 sided octagon 55' to each wall. The walls are vertical for 10', then angle off to rise to a peak some 40' above (with a nice little skylight way up there). The slope of course is quite dramatic. The sprinklers are about 12' on center along the pipe, but of course if you take a horizontal measurement, they are well inside the 6' minimum requirement. There are 42 sprinklers covering a floor space of roughly 3650 sq feet (if my math is correct). Pretty good density. I believe when we hashed this out before that the consensus was that NFPA said the ruling was to be applied along the slope. Would not this example be a prime candidate for an exception?

Regards
D

 

[cdafd]

so how far down is the first row or head down from the peak??

without a picture a little hard to make a call, but sounds like over kill

 

[MGXFP]

Personally I would take it up with the AHJ. A similar problem presented itself to me, only with a church of similar construction. Thankfully water pressures in the area were quite generous and a system was able to be worked out without a pump (this was a new addition to an existing structure, the riser being about 400' away and fed with 3" pipe).

Now, the second question is; are the sprinklers obstructed?

A thought experiment would indicate, given a fire, the heat would bank at the peak of the structure, setting off the uppermost sprinklers which then might lead to them cold-soldering the remainders, who might have activated otherwise.

In short, I would take it up with the AHJ and get something in writing.

 

[ContractorDave]

There are 2 sprinklers within the skylight at the top which is about an 8' peak. In each 'corner' of the octagon rising vertically are 12" beams and the sprinkler piping and heads have been installed on either side of every second beam with vertical sidewalls, so 8 lines with varying quantities of sprinklers... but mostly that's not relevant to my post. (leaves briefly to find earlier post...)

Actually cd it's your post of Feb 26/09 that began this... It was whether the 6' minimum was measured on the slope or horizontally.

After an interesting sequence of posts, SD2 quoted 13 / 8.5.3 and it seems to have been left at that.

I suppose this is a grey area that the FPE has to make a call on for a given situation: if the walls are vertical, then you only require sprinklers at the top. At what point past vertical will you add sprinklers for floor coverage vs. the requirements of 8.5.3 and does the 6' minimum ever come into effect?

Regards
D

 

[cdafd]

I just looked at my half barrel ceiling that is going up, and think the added lines is the correct call

lightecho

not a conceptual person , so hard to say without a picture

I have seen some crasy set ups for strange shaped ceilings, and some appeared correct and some appeared way off

 

[MaInspector]

In reading the first post I am wondering why the question is coming up, if it is being looked at during a required NFPA 25 inspection you should only be verifing that the system that was installed and approved works and not to see if it was installed incorrectly for coverage. Becareful siteing this in a inspection report. You may be taking liability for the entire system for no reason.

 

[ContractorDave]

Ahh , the infamous 'inspections to NFPA 25 quandary' that has so been bandied about here. Yes, we do the inspection to NFPA 25, using the ubiquitous AFSA format. We only call as a "deficiency" those things specifically listed as being a deficiency in 25.

That being said, I am a proffessional with specific knowledge in regards to public safety, and if I see an issue with how the system has been installed, I am obliged to notify the client. Liability is too often a cop out. If someone dies because you didn't say something, you're to blame whether others know it or not.

THAT being said, like most others on this forum, I merely pose interesting scenarios, real or fanciful, to learn what others think.

Regards
D