Omit Ceiling Sprinklers Entirely with All In-Rack?

12/19/2022

We have a project with a Class IV commodity rack storage area. The building has a roof slope around 24% (5.5 / 12).

Based on NFPA 13 2022 Edition, Section 20.9.1, one option for this case is "where storage is protected with in-rack sprinklers in accordance with one of the options in Section 25.6, provided no storage is placed above the highest level of in-rack sprinklers."

The question is: if a horizontal barrier and a level of rack sprinklers are installed above the last load level, and there is not going to be any storage above this level, can a system design be done based on 25.6 omitting the ceiling sprinklers?

The gap between the top of the load and the roof is about 6.5 meters in the highest area.

Thanks in advance.

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9 Comments

Glenn Berger

12/19/2022 08:11:20 am

Got a few questions to be answered prior to giving an opinion.

Is this "horizontal barrier" acting as a complete ceiling above the highest level of storage? Is this barrier fire rated? Is the space above the barrier accessible?

Eric R

12/19/2022 08:49:46 am

Not having any ceiling level sprinklers at all seems like a pretty far stretch unless a full drop ceiling was installed at the bottom of the trusses. Especially with what looks like pretty wide aisles, I'd be worried that a fire starting in product left in the aisles would not have sufficient coverage from sprinklers in the racks.

I'd recommend reading the phase 3 report from the NFPA Research Foundation on storage under sloped ceilings. NFPA 13-2025 already has some proposed revisions to cover these situations that you can also check out on NFPA's proposal platform.

Link for Research Foundation report: https://www.nfpa.org/-/media/Files/News-and-Research/Fire-statistics-and-reports/Suppression/rfslopedceilingPhase3.ashx

Link for 2025 proposed changes: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=13&tab=nextedition

Eric R

12/19/2022 09:08:00 am

Having a few more minutes to think about this, and I don't see any way ceiling sprinklers could be removed completely.

Some possible options:

1. Install a drop ceiling across the entire area to make your ceiling flat with sprinklers hung below that drop ceiling. Then you can follow the normal designs and may not need in-racks at all.

2. Use your proposed idea for covering all the racks per 25.6. Then provide a non-storage occupancy design for the ceiling system that covers all the floor area hazards not directly inside the racks. Following the rules for 25.6 I don't think you'd have to add the two system demands together, so this wouldn't increase your overall water requirement beyond what you already needed for your in-rack design. Ceiling design could probably be EH1 or maybe OH2 depending on what commodities are being stored in the facility.

3. Ask for a variance to follow the proposed changes for 2025 and the guidance from the research foundation. This might significantly reduce the design demands of the in-rack system compared to 25.6, but you'd really want to bone up on the limitations of the testing report and compare your storage commodity and arrangement to what they used in the report.

Franck

12/19/2022 10:18:03 am

The answer is definitely no.
Normally with such a slope, you can’t protect storage occupancy per NFPA 13, unless you provide a false ceiling (flat) with sprinklers underneath.
In some circumstances, it is accepted, for rack storage, to allow the slope with ceiling sprinklers + in-racks. That way it is like protecting a limited storage height with ceiling sprinklers. But they can’t be omitted. Even with in-rack above the last level.

In addition, with storage, there are many possibilities to have some storage not in the racks (between the racks, for receiving/dispatching) where the ceiling sprinklers will control slightly, but not the in-racks.

Jesse

12/19/2022 10:46:52 am

In this case, I don't see you being able to omit ceiling level AS

Alex

12/19/2022 02:28:48 pm

As others have mentioned above, I do not see a way to omit ceiling sprinklers here.

Mike Meyers link

12/19/2022 05:19:21 pm

I agree with all, never leave out the overhead sprinklers.
As a Fire Inspector I can tell you signs do not stop companies from stocking above a designated height.
It always becomes a policing problem when allowing so called grey area exceptions.

Alan Larson

12/21/2022 01:58:26 pm

Look at Section 25.8. If the top of the rack had a horizontal barrier with the first complement of in-rack sprinklers directly below that barrier, with in-rack sprinklers placed appropriately from there towards floor level, what would the ceiling level sprinklers be protecting? I realize the notion of no sprinklers at the roof deck is novel, but it seems this section may allow that.

Eric R

12/21/2022 07:21:43 pm

My intent is for this to come across in the spirit of good natured debate!

Your line of reasoning could easily be applied to many storage design criteria that seem strange at first. Like, why do we need to sprinkler a warehouse full of filing cabinets? Or better yet, a warehouse full of sheetrock! (I've actually had to handle the sheetrock example).

The answer is the same as it's always been, fully sprinklered buildings massively reduce the likelihood of casualties or property damage from fire. Sprinklers installed along the ceiling are 100% guaranteed to be above the height of any stored commodities. They are going to be where the hot gasses from a fire collect, and their spray is going to cool the air closest to the structural elements (if not soaking them directly), which will help prevent weakening or collapse.

A rack with a top horizontal barrier will need to have enough structural strength to at-least support the weight of the barrier and the topmost sprinkler piping. That's a whole lot of free real-estate to throw those extra bundles of cardboard boxes used for shipping. They don't weight to much, so go ahead and put them way up on top!

And then not much longer: Oh hey, that shelf up there is actually pretty sturdy. Lets put the pallets of empty 5 gallon buckets up there too. They take up a ton of space that we could really use to store all the extra product that's been piling up with these containership delays backing up the supply chain! We can move them back once things return to normal.

Which eventually(hopefully) leads to: What do you mean your giving me an abatement order!?! That stuff has been up there for years and you've never had a problem with it before! No, I can't just take it down, I don't have anywhere else to put it You're gonna put me out of business!

Now, if you want say that the criteria for the ceiling system is for a Class I entirely non-combustible commodity, and protect it at (checks quickly) 0.17 density using high temp 5.6k uprights, you can probably make that argument. Not having any protection at all though just creates to many opportunities for human behavior to get itself in trouble.

Omit Ceiling Sprinklers Entirely with All In-Rack?

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