How to Accommodate Closely-Spaced Sprinklers?

12/3/2019

Attached is a sketch of an interesting design issue we’ve been dealing with.

We have a convenience stair connecting multiple floors of an office building. With this, we need to treat the opening as an Atrium opening. So we have told the architect that we need a draft curtain with closely spaced heads.

The sketch attached shows some limitations that we’ve been given.

My question is, how would you suggest we accomplish the required protection given the constraints of this particular stair?

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7 Comments

Wayne Ammons

12/3/2019 08:50:51 am

What is the code basis for requiring a draft curtain as well as a water curtain?

Marc Vieno link

12/3/2019 11:14:51 am

Not the OP, so don't know the AHJ requirements/applicable code editions, but I'm going to try to answer this question from an IBC perspective.

2015 IBC §1019 prescribes protection for exit access stairs. Typically these need to be enclosed, however 1019.3 provides options for alternate methods of protection. Option 4 is a very commonly used one, and it requires (among other things) "...the opening is protected by draft curtain and closely spaced sprinklers in accordance with NFPA 13."

Hope that helps!

Marc Vieno link

12/3/2019 11:32:50 am

Assuming this opening connects more than 2 floors, and your code analysis is all in order.

This is a really tough situation, and is a good example of where subs can add value earlier on in the design process. If the building needs to meet the 2015 or 2018 IBC, I don't think it can meet the architects requirements and still be compliant. You may need to get creative with an AM&M by providing additional exiting (either more than code or closer than code), smoke detection, etc. Risky you have to convince the AHJ....

Jonathan Joseph

12/3/2019 12:27:27 pm

You would want to space your standard spray sprinklers to be spaced 6 feet apart and 6 inches off of the soffit all around the opening

NFPA 2016 8.15.4

If its 3 stories or less you might be able to use the Communicating Space rules of NFPA 101 8.6 and maybe eliminate the smoke barrier/draft curtain

Cliff

12/3/2019 12:35:20 pm

Would it be possible to create a ceiling pocket on the room side of the stair that would give you the 18" required?

Mike

12/3/2019 06:08:45 pm

Try "stepping " the acoustic panel so it is higher closest to the stairs.

SFFD Lt. JC

12/2/2020 02:08:00 pm

I'm not sure of the terminology, the design may be called an "Inverted Soffit", "Ceiling Trench", or "Heat Pocketed Water Curtain" (?). The sprinklers are installed in the Fire Rated Trench's (hard lid) above the ceiling. Heat accumulates in the pocket, and should activate the sprinklers simultaneously. I've seen these before at communicating openings, between buildings on the Property line, and around intervening stairs. If the entire depth of 18" can't be above the ceiling, it will reduce the obstruction of the draft curtain below (maybe only 4" - 8"). If it's not be code compliant, it may qualify as a local equivalency. Consult with your AHJ prior to design commitment.

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