Sprinkler for Very Sloped Residential Ceiling?

7/15/2022

I cannot find a residential sprinkler that will allow for sloped ceilings greater than an 8/12 pitch.

How can we approach this and still provide proper protection in a residential property?

Most log cabins have ceilings with a pitch up to 12/12. Thanks in advance.

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6 Comments

7/15/2022 08:18:46 am

In NFPA 13-R 2019 there is a code reference:

6.4.4* Where construction features or other special conditions exist that are outside the scope of sprinkler listings, listed sprinklers shall be permitted to be installed beyond their listing limitations.

It is further explained within the appendix:

A.6.4.4 Construction features such as large horizontal beamed
ceilings, sloped ceilings having beams, and steeply sloped ceilings exist that are outside of the current listings. In these situations, sprinklers can be installed in a manner acceptable to the authority having jurisdiction to achieve the results specified in this standard. In making these determinations, consideration should be given to factors influencing sprinkler system performance such as sprinkler response characteristics, impact of obstructions on sprinkler discharge, and number of sprinklers anticipated to operate in the event of a fire.

I have never used the code reference, but it seems to apply for your situation.

There is also the path of using quick-response sprinklers as per 13-R. However a hydraulic calculation using QR sprinklers is likely to be much more demanding and may exceed the typical residential water supply.

Alex

7/15/2022 10:28:40 am

Hi,

I didn't post the original question but glad someone did! I have never noticed 6.4.4 allowing the installations of sprinklers beyond their limitations.

Learn something new everyday!

Alex

Jesse

7/15/2022 08:40:24 am

Our colleagues on 13R thought of this. We can never fully address ever scenario in construction and architects like to continually challenge us.

In 13R it discusses: 6.4.4 *
Where construction features or other special conditions exist that are outside the scope of sprinkler listings, listed sprinklers shall be permitted to be installed beyond their listing limitations.

So, while indeed you won't the exact right sprinkler, this could be your path forward.

Eric

7/15/2022 08:53:34 am

JI has the right code reference for you.

In this situation you will have to design from a performance based approach.

You will want to consider the protection goals of NFPA 13D, and also consider how steeply pitched roofs effect the installation parameters of sprinklers in NFPA 13/13R systems.

If I was working on this project I would probably consider expanding the design area to include an additional sprinkler head similar to the 30% area increase in NFPA 13. I would also likely reduce the sprinkler spacing so a sprinkler would more likely be near the ignition point of a fire. This would also have the added benefit of reducing the overall water demand to help counter-act adding in the third design sprinkler.

I would also potentially space the sprinklers closer together running perpendicular to the roof pitch vs up the pitch. Though you would still need to use the flow/pressure requirements based on the longer separation.

I hope these ideas help!

Dave

7/15/2022 11:38:44 am

I haven't checked in a while, but the latest version (2018) of the old Viking Residential Sprinkler Guide seems t still address greater than 8:12
https://www.vikinggroupinc.com/sites/default/files/documents/080190_0.pdf

Reliable's design guide offers some guidance on page 8 of their design guide, including the possibility of flowing additional sprinklers, as has been suggested, and some AHJ's I know require this.
https://www.reliablesprinkler.com/files/pdfs/Residential.pdf?x31060&x95937

I think I've seen an informal NFSA interpretation on this but I can't find anything on their website now.

7/15/2022 04:37:09 pm

I recently completed a project with sloped ceilings greater than an 8/12 pitch. I talked to the AHJ and they asked that I a add an extra sprinkler to my hydraulic calculations per NFPA 13D, 2016 10.2.4.

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Sprinkler for Very Sloped Residential Ceiling?

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