How to Verify If Garage Uses IRC 309.5 Exception?

8/24/2021

There always seems to be controversy about residential sprinklers in the garage.

I recently came across a section in the 2018 IRC under Section 309.5 and it states that private garages shall be protected by fire sprinklers (must be residential or quick response, designed to 0.05 gpm/sqft density) where the exterior wall has been designed based on Table 302.1(2) Note A.

This table addresses minimum fire resistance ratings for exterior walls. Note (a) allows fire separation distance for non-rated exterior walls and projections to be reduced to 0-feet, unlimited openings and penetrations, with a setback, where residential subdivisions are all sprinklered.

While looking at that table, I am not sure how to verify on the sprinkler plans if the garage meets that design method.

I have started asking the contractor to add a note on the plans regarding the design method and if they use this table and note to design the wall then sprinklers are required in the garage.

How would you interpret this section for compliance?

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3 Comments

Alex

8/24/2021 07:37:21 am

Hi Anonymous,

I’m not exactly sure what you are driving at here. I’ve tried to summarize my thoughts below. Please let me know if you are looking for my thoughts/interpretation on something else!

If you are asking if you need to protect the garage with sprinklers, my interruption of IRC and NFPA 13R is yes. NPFA 13R 7.3 states the design criteria for garages (closely aligning with IRC).

Is your question in regards to separation distance? If so, you are correct, this brings you to Table R302.1(2), summarized currently in the third paragraph of your question. “This table addresses minimum fire resistance ratings for exterior walls. Note (a) allows fire separation distance for non-rated exterior walls and projections to be reduced to 0-feet, unlimited openings and penetrations, with a setback, where residential subdivisions are all sprinklered.”

Overall, my interpretation of the code is the following:
- Residential garages require automatic sprinkler protection. NFPA 13R 7.3 discusses the design density and when you need to follow NFPA 13 or NFPA 13R. I would recommend reading through this code section.
- Separation distance can be decreased if automatic sprinklers are installed within all dwellings. Separation distance should come from the architect/developer, not the FPE

Hope this helps somewhat!
Alex

Pete

8/24/2021 01:31:59 pm

Can you ask for any of the design drawings besides the sprinkler plans for verification?

Specifically, the structural plans. As those would likely tell you the wall type and potentially the fire rating.

Johnathan Hurst

8/24/2021 01:41:49 pm

Hello Anonymous,
Whereas your code interpretation is correct, as is that of Alex, who has already replied, as a former Building Official / Fire Marshall, I would strongly advise that a note be placed on the plans stating the parameters of the code that allowed sprinklers to be omitted.
I have seen numerous times in housing tracts that a new homeowner would request a special modification to their home. These modifications could range from windows in the garage to changes in the house to garage separation. Having the specific note on the plans might have the benefit of the prevention of additional openings or perhaps the addition of sprinklers in certain homes where these modifications have taken place.

How to Verify If Garage Uses IRC 309.5 Exception?

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