Room Design Method Allowed for Hotel Room?

10/14/2025

I am working on an NFPA 13 hotel where the most demanding guest room is protected by 3 sprinklers: 1 sidewall (16x20) and 1 pendent (14x14) in the guest space, which totals 275 ft², and 1 pendent (14x14) in the bathroom.

If the room meets all the requirements for the room design method, am I required to pick up a 4th sprinkler from the corridor?

If not, then based on Section 19.4.1.3, would the sidewall sprinkler be allowed to use the listed flow, as the room area divided by 2 sprinklers would be less in this case?

Thanks in advance.

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9 Comments

Anthony

10/14/2025 08:21:00 am

Use the regular compartment method with residential sprinklers. you're never 'required' to use room design method.

Ensure all the sprinklers you're using are residential listed sprinklers. Also ensure you're flowing the correct end head pressures.

Connor R

10/14/2025 09:56:49 am

Regarding the listed flow, NFPA 13 2025 requires you to calculate the greater of the listed flow or the minimum to cover the area. As the compartment is less than 800 sq ft, each sprinkler can be calculated at either the listed flow or the area of each room divided by the number of sprinklers times 0.1 gpm/sq ft, whichever is greater.

19.3.1.3
The minimum required discharge from each design area sprinkler shall be the greater of the following:
(1)
In accordance with minimum flow rates indicated in the sprinkler listings

(2)
In rooms or compartments greater than 800 ft2 (74 m2), calculated based on delivering a minimum of 0.1 gpm/ft2 (4.1 mm/min) over the design area in accordance with the provisions of 9.5.2.1

(3)
In rooms or compartments 800 ft2 (74 m2) or less calculated based on delivering a minimum of 0.1 gpm/ft2 (4.1 mm/min) over the room or the compartment using the area of the room divided by the number of sprinklers in the room

Jose Figueroa

10/14/2025 10:06:27 am

Exactly that

10/15/2025 05:52:30 am

Hello. I may be misunderstanding something... If you have a sidewall spraying 20'x16' and 2 pendents spraying a space smaller than 12'x12'; you are saying to simply add the spray area of the 3 sprinklers and simply divide by 3 and use this area as your area per head? The sidewall is going to require a lot more gpm and psi than those pendents

Jesse

10/14/2025 11:57:43 am

A morning of meetings so I'm late to the party! Anthony and Connor covered it well. What they said!

Mark Harris

10/15/2025 01:24:39 pm

S. As Connor notes you have to meet minimum listings. Your extended coverage sidewall will determine starting pressure and then your pendent sprinklers will overdischarge as the calc pressure at the pendents will typically be higher than required to meet minimum design. With the area the pendents cover even 7 PSI would provide more than .10 GPM/SF but you don't mention what EC sidewall listed minimum pressure is but going to assume much higher than 7 PSI.

10/16/2025 07:43:42 am

i appreciate your answer and I realize this, but my question was about taking the 3 sprinklers, adding up the total square feet and simply dividing the area by 3... with an extended coverage head as shown, how can that answer be correct... by evenly dividing the area by 3, haven't you just reduced the required area of protection of the extended coverage sidewall. this is where my confusion is.

James Art, FPE

10/15/2025 02:44:20 pm

Doing it with extended coverage sidewalls, as shown,
is code legal.
However, might not be in the best interests of the building.
In several actual incidents,
fires near the windows, have spread outside to floors above.

Also consider the required sprinkler design parameters for protection of the hallways.
Section 11.2.3.4.2 suggests it should be 7 sprinklers since they form a line down the corridor.

Section 11.3.1.1 suggests that it should only be 4 sprinklers if they are residential-type.

For some codes: With an automatic sprinkler system: If the building is equipped throughout with a supervised automatic sprinkler system, the required rating for WALLS separating guestrooms may be reduced to 1/2-hour.

Ryan S

10/16/2025 10:46:13 am

If you are using residential sprinklers, as per 19.4.1.1 (NFPA 13 - 2019), the design area shall be the area that includes the four adjacent sprinklers that produce the greatest hydraulic demand. If you only have three sprinklers in one compartment, you must include another adjacent sprinkler.

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Room Design Method Allowed for Hotel Room?

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