Use 2-Hour Gyp. Chase for Standpipe Protection?

3/28/2025

Section 9.2.2 in NFPA 14 allows protection for a standpipe that is not in a stairway to be "the piping is enclosed in fire-rated construction with a rating equal to that of the enclosed fire-rated exit stairway."

In the Gypsum Association Manual WP 3910 for a chase wall with staggered studs has a rating of 2 hours.

Does such a 2-hour rated chase meet the intent of NFPA 14 when the standpipe is not in the stair?

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11 Comments

Dan Wilder

3/28/2025 07:51:25 am

Possibly....for some projects we have dealt with in the past

If the standpipe resides between two of these wall assemblies, then yes it complies assuming the top and bottom wall caps and floor/ceiling-roof deck meets the same rating for the construction.

If the intent is to run the standpipe within the wall then no as the rating is based on a symmetrical rating utilizing both sides of the wall.

A better option would look closer to a rated shaft wall or soffit with an asymmetrical rated wall construction (all the gyp board on one side) as this allows construction without access to one side of the wall/soffit system and maintains rating.

Look at UL Design V497 for examples or WP7125 looks similar to what I have seen in the past.

Paul Pinigis link

3/28/2025 08:15:00 am

You can build an enclosure with this wall construction, but you cannot install the pipe within the wall because that would not provide the required 2-hour protection. The 2-hour rating of this wall is from one side of the wall to the other, not from one side of the wall to the interior of the wall.

Additionally This wall would either have to be free-standing from the slab-on-grade or would have to be supported by 2-hour floors that are supported on 2-hour structure.

Glenn Berger

3/28/2025 08:18:08 am

A 2-hour fire-rated chase can be constructed to meet the requirements in NFPA 14. Additional detailing will need to be completed to achieve compliance with the reference provided.

Adam

3/28/2025 08:42:43 am

In Ontario, fire-rated walls are based on the fire resistance of one side to the interior, but they need to be constructed with an equal rating on either side.

Once the fire has penetrated the membrane of the wall, the structure is then in direct contact with the fire. The gypsum on the opposite side of the wall does not have support once the studs have burned away.

The two layers of Type-X give you a 2-hour rating on the side that it is installed, but having two layers on each side does not achieve a 4-hour rating because the structure starts to burn once the exposed side is compromised.

I would say that installing the pipe within the wall is acceptable.

Paul Pinigis link

3/28/2025 08:47:32 am

I am not aware of any calculation that equates two layers of Type X gypsum board to a 2-hour fire-resistance rating. The listed endurance for 5/8" Type X gypsum board is 40 minutes, so 2 layers provides 80 minutes of protection. You could use thicker gypsum board, but the detail provided utilized 5/8"

Adam

3/28/2025 08:58:59 am

The Ontario Building Code describes the "component additive method" which takes into account the framing and any insulaton as well. This can bring you up to 115 minutes with insulation - just shy of 2-hours. In addition to this calculation, the OBC provides approved fire- and sound-rated assemblies in their supporting documentation. Many of these assemblies, rated for two hours include two layers of type-X. It's also not uncommon to find UL-listings that allow this (similar to the example in the OP). So while a calculation method might not bring you to two-hours, the right listing or documentation will allow it.

Jack G

3/28/2025 10:27:57 am

It is my understanding that in fully sprinklered buildings a 1 hr enclosure is required, 4 or greater 2 hour.
So any rated enclosure appropriate for the standpipe can be used.
The enclosure is also included for laterals ( to hose valves, laterals of class 1 standpipes shall be protected with a degree of fire protection equal to that of an exit stair, exception being fully sprinklered buildings. Here’s the sticky part. IBC definition of laterals is from the 2013 edition of NFPA 14, which , by the IBC will require lateral and supply enclosure of the piping if not enclosed in the exit stair.
Later editions ( NFPA 14) do not require the enclosure for laterals/ supplies for standpipes, but the IBC definition is stuck with the 2013 definition.
Horizontal standpipes ( single story) are another animal and can be fire wrapped.

Jesse

3/28/2025 11:21:38 am

The short answer is "yes".

The longer answer is that the GC needs to ensure the standpipe main is in a chase that really is 2-hr rated. We had a project we designed like this in a hotel renovation where the GC provided 1-hr rating on both sides of the chase - and 1hr + 1hr = 2hr right??

Jeff Ayers

3/28/2025 11:57:51 am

The short answer is ACTUALLY NO. Because 2-hour shaft enclosures are typically only required for multiple stories and the wall type shown is for 1 level.

Why? Because the standpipe for the FHV is penetrating more than one floor ceiling assembly. The wall detail you show is designed to be installed from slab to ceiling, not continue up multiple levels.

The 2-hour shaft will be installed UNINTERRUPTED from the second floor up through all subsequent floors. (Most shaft walls can stack up to 45' and 1 UL assembly allows up to 65' vertical stacking.

In IIIA (5 level) and podium projects up to 2 levels (2 levels max to avoid being classified as a high-rise at 75' from apparatus access) the shaft will start on top of the podium and extend through the top level. The shaft wall is typically UL U428 and it sits in front of the corridor demising wall, allowing an opening in the floor at each level for the shaft wall to stack.

Note that some AHJ's want the horizonal runs from the standpipe in the stairwells to be 2- hour- running laterally to the vertical standpipe. Others allow the horizontal to be run in the truss spaces which is a 1-hour floor ceiling assembly.

The wall assembly you show would only work at 1-story assemblies. In that case the lateral being fed through the ceilings will turn down into the 2-hour wall you have shown.

Todd E Wyatt

3/31/2025 10:06:33 am

The fire-resistance rating (FRR) of an Interior Exit Stairway (IES) should be determined by the Design Professional (e.g. Architect). The FRR of the IES is determined by both the number of stories it connects (1-Hour <4 stories or 2-Hours >4 stories) and the FRR of the Floor Assembly it penetrates :

IBC-2024
Chapter 10 Means of Egress
Section 1023 Interior Exit Stairways and Ramps
1023.2 Construction
Enclosures for interior exit stairways and ramps shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both. Interior exit stairway and ramp enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more and not less than 1 hour where connecting less than four stories. The number of stories connected by the interior exit stairways or ramps shall include any basements, but not any mezzanines. Enclosures for interior exit stairways and ramps shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.

The "Protection of Piping from Fire Damage" has (4) methods listed ...

NFPA 14-2024
9.2.2 Protection of Piping from Fire Damage.
Class I and Class III standpipe system aboveground piping shall be protected from fire damage by one of the following methods:
1. The piping is enclosed in a fire-rated exit stairway.
2. The piping is enclosed in fire-rated construction with a rating equal to that of the enclosed fire-rated exit stairway.
3. Listed fire wrap or other insulating material is applied directly to the pipe with a rating equal to that of the enclosed fire-rated exit stairway.
4. Other methods acceptable to the AHJ.

... but IF the building is already protected by an automatic sprinkler system (ASPS), then "horizontal standpipes" not located in a FRR stair enclosure are req'd to be protected :

9.2.2.4*
Where buildings are fully sprinklered in accordance with NFPA 13 or NFPA 13R, feed mains, express mains, express risers, HORIZONTAL STANDPIPES, and branch lines that are not located in rated stair enclosures shall not be required to be protected from fire damage.

Here are other exceptions for NOT protecting standpipes from fire damage :

9.2.2.1
Where exit stairways are not required to be enclosed in fire-rated construction, standpipe systems shall not be required to be protected from fire damage.
9.2.2.2
Class II standpipe system piping shall not be required to be protected from fire damage.
9.2.2.3
Where additional standpipes are provided outside of stair enclosures to meet travel distance requirements in non-high-rise buildings, protection of additional standpipes from fire damage shall not be required.

Todd E Wyatt

4/3/2025 01:40:27 am

CORRECTION ...

... but IF the building is already protected by an automatic sprinkler system (ASPS), then "horizontal standpipes" not located in a FRR stair enclosure are NOT req'd to be protected ...

Use 2-Hour Gyp. Chase for Standpipe Protection?

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