Does 60-ft Military Hangar Need K-11.2 Sprinklers?

3/20/2025

We are working on hydraulic calculations for a military hangar, and we are referencing UFC 4-211-01, which calls for the design area to be 0.20 over 5000 sqft.

The hangar is 60 feet tall at its peak. To prevent overflow, we are proposing K5.6 sprinklers for the area.

Are K5.6 sprinklers allowed, or does UFC 3-600-01 apply where buildings 45-ft up to 60-ft would require minimum K11.2 sprinklers?

The area is overflowing by around 600 gpm. Any advice on this would be helpful. Thanks.

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11 Comments

Pete H

3/20/2025 06:47:27 am

I see no reason 3-600-01 chapter 9 wouldn't additionally apply as those seem to be general requirements. Specifically Table 9-3.

I realize the requirements of UFC 4 211 01 3-6.15 does increase the design area to 5000 square feet from what is required in that table, but I'd still give them the 11.2 heads required for that height/hazard in 3-600-01.

That said, new codes to me, so I can be completely incorrect.

Glenn Berger

3/20/2025 08:13:43 am

Your project will need to be in compliance with both UFCs. You can try to submit an RFI explaining the situation.

Jesse

3/20/2025 09:05:13 am

Uggggg UFC....

I don't think you'll be able to use K=5.6 here. Yes, it will may very well work. Yes, it may very well calc. Yes, you can make a rational reason to do it.

But UFC is a monster.

I had a convenience store on a DOD installation that wowuld have worked fine - but eneded up needing a pump because of the UFC requirements

Jack G

3/20/2025 09:35:01 am

I m wondering why nfpa 409 doesn t come into play.
For closed head water systems it specifies a .16 over 5000 sq. Ft.
Also foam water, and oscillating monitor nozzles. Depending in type of hanger.
It also indicates k factors of 5.6, 11, 8.0.
It looks like it is also listed in chapter 35, IBC, under NFPA phamplets
Nfpa indicates following nfpa 409 for aircraft hangers.
The type of hanger-- type 1,2,3,or 4.
Need more informatiin.

CHRIS LIZAKOWSKI

3/20/2025 10:33:09 am

It is a Class II Hangar. The UFC overrules NFPA 409.

Jerry Clark

3/20/2025 10:01:05 am

We need to know if this is a Group I or Group II hangar. That will dictate the type of system required.

CHRIS LIZAKOWSKI

3/20/2025 10:30:56 am

It is a Class II hangar

Steven A Waidelich

3/20/2025 01:05:46 pm

UFC 4-211-01, change 3 requires 11.2

Brett

3/20/2025 01:53:47 pm

If UFC 4-211-01 doesn't specifically alter the requirements of UFC 3-600-01 then UFC 3-600-01 applies. UFC 4-211-01 doesn't mandate a specific k-factor so you have to follow UFC 3-600-01.

Essentially what's happening here is UFC 4-211-01 is overriding the design area requirement from UFC 3-600-01 but it is not altering the k-factor requirement.

It still wouldn't hurt to RFI the QFPE or DFPE (not sure if you're the QFPE or contractor).

Chris Cahill

4/2/2025 01:50:11 pm

The Chief FPE of the AF has ruled k5.6 is acceptable on multiple occasions, pre and post Sundown Policy.

Chris Cahill

4/2/2025 02:39:08 pm

Sorry, didn't complete thought...this was as recent as two weeks ago.

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Does 60-ft Military Hangar Need K-11.2 Sprinklers?

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