Room Design / Less than 4 sprinklers / Residential heads

[LayoutLabor]

thread184-303963

It's seems this topic was touched on but not was not completely defined. Currently working on 4 story hotel, a project for Marriott using the Module 14 guidelines. Half of the guest rooms can be protected with 3 sprinklers in them and the other half have 4. Residential sprinklers have been selected using a .10 density per Mod 14. Increasing the spacing in the smaller guest room allows for one less sprinkler but at a higher pressure using (SxL) at .10.

Can the room design method be used for residential sprinklers?
Can a design area ever be less than 4 sprinklers? (using the room design method)

Provided each guest room is surrounded by a 1 hour wall, has a automatic closing door and separate calculations are provided for each of the guest rooms.

NFPA 13, 11.3.1 specifies a 4 sprinkler design area, but does not exclude the room design method.
NFPA 13, 11.2.3.3 defines the room design method but does not exclude the use of residential sprinklers or a room designed with less than 4 sprinklers.

It appears that the room design method can be used for most any hazard classification so why not residential sprinklers.

Thank for your time and this forum.

Steven Davis

 

[TravisMack]

Remember that if you have a small room, you don't have to use SxL. You can use the area of the room divided by the number of sprinklers in the room to get the area per sprinkler. You then take that x 0.10 to get the minimum density. If using residential sprinklers, you compare that to the listing of the sprinkler at the spacing indicated and use the greater of the two. (reference NFPA 13, 2013 11.3.1.3 which leads you to 8.5.2.1 or 8.6.2.1.2)

For example, you have a room that is 500 sq ft protected by 3 sprinklers. The area per sprinkler is 167 sq ft. So, you must do a minimum of 16.7 gpm. If you sprinklers are spaced 8' or less off walls and 16' or less on center, the minimum from the data sheet for 4.9k sprinklers is 13 gpm. You would have to use 16.7 gpm for your calcs. If you are 18' spacing, then you would use 17 gpm from the data sheet. If you are 20' spacing, you are going to use 20 gpm.

I think most don't use the room design because Chapter 11 - Design approaches has the specific instance for residential sprinklers. Also, IMO, if you use room design, and not 11.3.1, you can't get to 8.6.2.1.2. (8.6 is for standard spray. You can only use it because 11.3.1 points you there Therefore, you would have to use SxL. So, with room design, if I were 10' off the north and 10' off the west wall, I would have to calculate 40 gpm per sprinklers. That would force me into larger k-factors and higher pressures. In my example above, the same situation of 10' off two walls would only mean 20 gpm. I would bet calculating the 4th sprinkler would likely be better. I can have 3 at 40 gpm for a total of 120 gpm, or 4 at 20 gpm for a total of 80 gpm. It seems the residential allowances would give me smaller pipe sizing and less water demand.

So, I am not positive that you can't use the room design method with residential sprinklers. However, I don't know that it will be of any benefit to you.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[dssprdesigner]

I'm not sure what Module 14 is, but if it is a 4 storey building, could it not be designed to NFPA 13R?

13R allows you to calculate a compartment up to 4 sprinklers.

 

[LayoutLabor]

Mod 14 is the Marriott Module for fire protection. They have some specific guidelines for location of valves, inspector tests, type of sprinklers used, and density adjustments. One of these is all guest rooms are factored at a .10 density another being Exhibit/Ball Rooms are a .15 density.

Travis gave me a great idea, using the provision provided in NFPA 13, 2013 11.3.1.3 leading to 8.5.2.1 or 8.6.2.1.2. I haven't been excited about something in a while and this provision really made my day when it worked for all of the guest room calculations. Especially when this project requires that the 4th floor be fed from the 3rd floor using what we like to refer to as a bird cage. (3rd and 4th floor are separate system per Marriot Mod 14)

Still not 100% sure about these 2 questions, even though they are no longer applicable.

Can the room design method be used for residential sprinklers?
Can a design area ever be less than 4 sprinklers? (using the room design method)

NFPA 13, 11.3.1 specifies a 4 sprinkler design area, but does not exclude the room design method.
NFPA 13, 11.2.3.3 defines the room design method but does not exclude the use of residential sprinklers or a room designed with less than 4 sprinklers.


Thanks for the prompt replies.

 

[TravisMack]

dss:

Be careful with applying 13R to all residential buildings 4 stories or less. You must first follow the building code. Assuming you are in IBC lands, you must look at IBC Table 503 for allowed areas. If the architect has used the sprinkler increase to get the size of building footprint that is required, then you are mandated to do NFPA 13, not NFPA 13R.

If you have Type VA construction of 3 stories and 26000 sq ft per floor, there is no way to make that an NFPA 13R system per the IBC.

Area modifications are in section 506. 506 states that if the building is fully sprinklered in accordance with Section 903.3.1.1 then you can increase the area 200% per floor for a multi-story building or 300% for a single story building. So, in the example above, that building is going to be NFPA 13 all day long.

I see way too many architects that don't get this correct. People often skim these sections and just see sprinkler increase gives area increase. If you don't read the fine details, you are going to run a high liability for a system that is not in compliance with the adopted building code.

I will admit that I see a lot of sprinkler contractors apply NFPA 13R to these buildings incorrectly as well. As sprinkler guys, we often only focus on NFPA requirements, but you also have to be aware of the governing building codes as well.

Remember, code trumps standard.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[TravisMack]

Layout:

I believe you can use the room design with residential sprinklers. The question would likely be "Why would you want to?" You will be limited to SxL, so you may as well use Ex Cov sprinklers and get the larger orifices they offer. I'm sure there will be the rare case where the small room rule would be beneficial. However, like with a typical hotel room, you don't have self closers going into the bathrooms, so you would calculate the sprinklers in the sleeping area and the bathroom. But, I am sure there is a case where it would be beneficial. I have just not run across them in a long time - if ever.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[stookeyfpe]

Be careful with applying 13R to all residential buildings 4 stories or less. You must first follow the building code. Assuming you are in IBC lands, you must look at IBC Table 503 for allowed areas. If the architect has used the sprinkler increase to get the size of building footprint that is required, then you are mandated to do NFPA 13, not NFPA 13R.

If you have Type VA construction of 3 stories and 26000 sq ft per floor, there is no way to make that an NFPA 13R system per the IBC.

Actually, you can. If one subdivided the building with a 2-hour fire wall, one can create two buildings for the purposes of IBC (or Canadian Building Code). For the purpose of sizing the means of egress, this two-hour fire wall can be used as a Horizontal Exit, which introduces the issue of requiring a Standpipe hose valve on both sides of the wall - IF - your interior hose lay distances exceed code prescribed limits.

I have many buildings in my jurisdiction (primarily Cities in a Box) that are a mix of NFPA 13 and 13R because the building is divided with 4-6 fire walls.

 

[dssprdesigner]

I'm not in IBC land, and our building code is more relaxed in defining where we can use NFPA 13R in lieu of NFPA 13.

To really simplify it:

-Does the building require sprinklers - yes or no
if yes then go to NFPA 13 - unless -

it is a residential occupancy not more than 4 storeys or a care occupancy that has sleeping accommodations for not more than 10 ppl and not more than 6 ppl are non-ambulatory​

then go to NFPA 13R - unless -

the building is a residential occupancy not containing more than two dwelling units​

then go to NFPA 13D

 

[TravisMack]

Scott:

We are seeing architects do that quite a bit now.

I was trying to point out that not all 4 story or less residential buildings are ok for 13R.

DS:
If you are not under the IBC, then you may have lesser requirements. For those of us governed by the I-codes, then we can't just jump right to 13R. However, most I come across try to make that jump.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[TravisMack]

This thing comes up very often. Just a few minutes ago, I had to show an architect again where IBC states for the area increase you must go to 903.3.1.1 which is 13. All too often people just think residential and up to 4 stories is NFPA 13R. That is not always the case. Be careful as you are going through projects.

I am curious as to what area dssprdesigner is working where they are not following the I-codes. Not that I question it, but just wanting to learn about the areas in the US and abroad. That does give more flexibility in these residential projects.

Travis Mack
MFP Design, LLC

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