Avoid Sprinkler in Above-Ceiling Space with OSB?

7/24/2023

We have an original 17,000 sqft building built during the 1970's which has a masonry deck on OSB boards on steel structure. The original building had a continuous gypsum board ceiling at the bottom of the trusses, and no sprinkler system. Lay-in ACT ceilings have been added over the years and a lot of the gypsum board has been damaged or removed.

Due to the exposed OSB boards, we've listed the structure as Type V-B. As part of the new project in the building, we will be adding a sprinkler system.

Is there a code-compliant way to avoid sprinkler protection above the ceilings?

Perhaps a post-factor spray-on fire retardant?

Thank you for your input.

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

7 Comments

Glenn Berger

7/24/2023 08:08:13 am

This is a discussion point with the AHJ and others having interest in the building.

Sprayed-applied fire coatings may appeased those who are the decision makers.

Dan Wilder

7/24/2023 08:42:30 am

This will likely be an AHJ call so I'm speaking on what would likely happen in my neck of the woods...it's going to be sprinklered above and below. If the deck was fire-treated, those chemicals are not forever and I would hardly call an entire roof deck "limited" or "minimal". The space is deeper than 6". The access needed for hanging also presents an issue as the will need to be access holes for the field to install the hangers to the structure. The costs would be better spent for all installing trades to have clear access to the structure by demo of the lower gyp board in lieu or access & repair.

Even if there is an acceptable spray on application available, there is still the need for access to the structure for applying it, i.e. demo and I'm betting uprights are a cheaper option.

Jon N

7/24/2023 10:03:04 am

By definition in the codes, fire-retardant treatments for (fire-retardant-treated - FRT) lumber can only occur during the manufacturing process of the lumber. To the best of my knowledge, there is no after-market spray, brush, or roller-applied products that will make ordinary lumber into FRT lumber.

There are products that will reduce the flame-spread rating but this is different than making it FRT. There are also intumescent coatings that will swell up when exposed to heat and can protect the wood. The downside is that these products have a shelf-life, very specific application instructions and may be susceptible to weathering conditions. The intumescent coatings tend to be somewhat expensive (likely cheaper to do above/below sprinklers).

Be very cautious of after-market products claiming to be able to make combustible materials (like wood) non-combustible. Also, be cautious of any product claiming to be able to make wood FRT. These products can reduce flame spread ratings but cannot make wood non-combustible or FRT. Very easy to get confused with similar-sounding terminology. Beware of companies claiming to have some magic "pixie-dust" in their product that can make things non-combustible or FRT.

7/27/2023 04:51:46 pm

What about NFPA 13-2019 omission allowances:

9.2.1.7 Concealed spaces filled with noncombustible insulation shall not require sprinkler protection.

9.2.1.8 Concealed spaces within wood joist construction having noncombustible insulation filling the space from the ceiling up to the bottom edge of the joist of the roof or floor deck shall not require sprinkler protection.

Todd E Wyatt

8/1/2023 08:43:10 am

You are correct ... NFPA 13 permits ommissions of an automatic sprinkler system (ASPS) including "concealed spaces."

The post includes (2) related but independent issues : Type of Construction (TC) and the scoping requirements for an Automatic Sprinkler System (ASPS).

Type of Construction
The original design may have used a listed floor/ceiling or roof/ceiling assembly (" ... original building had a continuous gypsum board ceiling at the bottom of the trusses ...") that provided the required fire-resistance rating (FRR) as required for the building's Type of Construction (TC). The TC will determine the "allowables" (building area, building height, number of stories) along with the Occupancy Classifications (OC) and whether the building is protected by an ASPS.

Adding Spray-Applied Fireproofing Materials (SFRM) to individual components (beams, trusses, columns, etc.) of the building's structural system is a valid solution to meet the minimum fire-resistance ratings (FRR) per its TC. The SFRM does not affect the requirement to protect this area with an ASPS, however.

ASPS Scoping
The scoping Code (e.g. 2021 IBC) will determine IF an ASPS is required based on the building's Occupancy Classification (OC) per Chapter 9 Fire Protection and Life Safety Systems, Section 903 Automatic Sprinkler Systems, 903.2 Where Required. The IBC references "NFPA 13 Standard for the Installation of Sprinkler Systems" as the standard for sprinklers' installation, testing, & maintenance. NFPA 13 Section 9.2 contains a consolidated list of specific locations where sprinklers can be omitted. This Your post includes (2) related but independent issues : Type of Construction (TC) and the scoping requirements for an Automatic Sprinkler System (ASPS).

Type of Construction
The original design may have used a listed floor/ceiling or roof/ceiling assembly (" ... original building had a continuous gypsum board ceiling at the bottom of the trusses ...") that provided the required fire-resistance rating (FRR) as required for the building's Type of Construction (TC). The TC will determine the "allowables" (building area, building height, number of stories) along with the Occupancy Classifications (OC) and whether the building is protected by an ASPS.

Adding Spray-Applied Fireproofing Materials (SFRM) to individual components (beams, trusses, columns, etc.) of the building's structural system is a valid solution to meet the minimum fire-resistance ratings (FRR) per its TC. The SFRM does not affect the requirement to protect this area with an ASPS, however.

ASPS Scoping
The scoping Code (e.g. 2021 IBC) will determine IF an ASPS is required based on the building's Occupancy Classification (OC) per Chapter 9 Fire Protection and Life Safety Systems, Section 903 Automatic Sprinkler Systems, 903.2 Where Required. The IBC references "NFPA 13 Standard for the Installation of Sprinkler Systems" as the standard for sprinklers' installation, testing, & maintenance. NFPA 13 Section 9.2 contains a consolidated list of specific locations where sprinklers can be omitted. This includes "concealed spaces" which the original listed floor/ceiling or roof/ceiling assembly probably met and may have permitted the omission of an ASPS in these concealed areas. Now that the listed floor/ceiling or roof/ceiling assembly does not define a concealed space, it may have to be protected with an ASPS. which the original listed floor/ceiling or roof/ceiling assembly probably met and may have permitted the omission of an ASPS in these concealed areas. Now that the listed floor/ceiling or roof/ceiling assembly does not define a concealed space, it may have to be protected with an ASPS.

Todd E Wyatt

8/1/2023 08:43:57 am

REFERENCES

2022 NFPA 13 Standard for the Installation of Sprinkler Systems
Chapter 9 Sprinkler Location Requirements
9.2 Allowable Sprinkler Omission Locations.

ENHANCED CONTENT
Section 9.2 contains a consolidated list of specific locations where sprinklers can be omitted. It was developed to consolidate all the specific allowances that were scattered throughout Chapter 8 of the 2016 edition.

Section 9.2 can be expected to be a very active part of NFPA 13 during future revision cycles. It is the one section where the basic principle of NFPA 13—that sprinklers must be installed throughout the premises—is allowed to be altered. During each code development cycle, the Technical Committee on Sprinkler System Installation Criteria acts on inputs and comments seeking to “excuse” a specific portion of a building from the requirements of sprinkler protection due to a special situation. The case is typically made that, under certain conditions, the presence of sprinklers does not provide any greater protection, and the omission of sprinklers in those specific areas and spaces within a building should be permitted. (Section 9.3 identifies those spaces and conditions.)

It is important to note the following two points regarding Section 9.2:
It is imperative that when the elimination of sprinklers from a space based on Section 9.2 is being considered, the space must comply exactly with the description and requirements found within the applicable paragraph(s). In other words, any deviation from the description in an applicable paragraph negates its application, and, as a result, the space must be sprinklered.
If a space is not specifically detailed in Section 9.2, it is intended to be protected by sprinklers under 9.1.1(1).

9.2.1* Concealed Spaces Not Requiring Sprinkler Protection.

ENHANCED CONTENT
The paragraphs and subparagraphs of 9.2.1 specify conditions where sprinklers are not required in concealed spaces that normally would require sprinklers. Sometimes the building is modified to meet one of those exceptions to avoid installing sprinklers in the space. Not all the exceptions provide an equivalent level of fire safety, because some of the exceptions simply recognize that the installation of sprinklers in the space is not physically practical. This difference in level of fire safety is especially true of 9.2.1.3 , 9.2.1.4 , and 9.2.1.5, which primarily exist to cover situations where sprinklers are retrofitted into existing buildings.

NFPA 13 is a minimum standard for the protection of property as well as for life safety. Many authorities having jurisdiction recognize the “Murphy’s Law” aspect prevalent in the experiences of the fire service, in that a lightning strike could start a fire in such a concealed space.
It is important to note that omitting sprinklers in these spaces might require an increase in the area of operation of the sprinkler system as determined in 19.2.3.1.5. Therefore, A.9.2.1 provides a pointer to ensure a complete evaluation of the impact of omitting sprinklers.

ASK THE AHJ
Are fire sprinklers required in combustible concealed spaces that are entirely on the outside of the building, such as the spaces formed at the eaves of a truss roof or at false facades on the side of the building, where there are no ignition sources?
Yes, unless one of the exceptions in 9.2.1 can be applied.

9.2.1.1*
Concealed spaces of noncombustible and limited-combustible construction with minimal combustible loading having no access shall not require sprinkler protection.
9.2.1.1.1
The space shall be considered a concealed space even with small openings such as those used as return air for a plenum.
9.3 Special Situations.
9.3.17 Concealed Spaces.
9.3.17.1 Concealed Spaces Requiring Sprinkler Protection.
Concealed spaces of exposed combustible construction shall be protected by sprinklers except in concealed spaces where sprinklers are not required to be installed by 9.2.1.1 through 9.2.1.20 and 9.2.2.
9.3.17.1.1* Concealed Space Design Requirements.
Sprinklers in concealed spaces having no access for storage or other use shall be installed in accordance with the requirements for light hazard occupancy.

9.3.17.1.2 Localized Protection of Exposed Combustible Construction or Exposed Combustibles.
When otherwise noncombustible or limited-combustible concealed spaces that would not require sprinkler protection have localized exposed combustible construction, or contain localized areas of exposed combustibles, the c

Todd E Wyatt

8/1/2023 08:45:00 am

REFERENCES continued ...

2022 NFPA 13 Standard for the Installation of Sprinkler Systems

9.3.17.1.2 Localized Protection of Exposed Combustible Construction or Exposed Combustibles.
When otherwise noncombustible or limited-combustible concealed spaces that would not require sprinkler protection have localized exposed combustible construction, or contain localized areas of exposed combustibles, the combustibles shall be permitted to be protected as follows:
If the exposed combustibles are in the vertical partitions or walls around all or a portion of the enclosure, a single row of sprinklers spaced not over 12 ft (3.7 m) apart nor more than 6 ft (1.8 m) from the inside of the partition shall be permitted to protect the surface. The first and last sprinklers in such a row shall not be over 5 ft (1.5 m) from the ends of the partitions.
If the exposed combustibles are in the horizontal plane, the area of the combustibles shall be permitted to be protected with sprinklers on a light hazard spacing. Additional sprinklers shall be installed no more than 6 ft (1.8 m) outside the outline of the area and not more than 12 ft (3.7 m) on center along the outline. When the outline returns to a wall or other obstruction, the last sprinkler shall not be more than 6 ft (1.8 m) from the wall or obstruction.

Avoid Sprinkler in Above-Ceiling Space with OSB?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES