Site Fire Flows

[TravisMack]

This is a follow up to the previous question on height and areas as it is for the same project. Again, this is not in my scope, but we get thrown in the middle when the building department approved everything, then the fire department comes in and rejects the project and our deferred submittal because they believe the code study was incorrect.

When determining the values to use in site fire flow calculations, do you use the largest (or most demanding) single building on a project, or the floor areas of ALL of the buildings on the project site? For example, there are multiple apartment buildings on this site. The total area would require more site fire flow than is available at the site. If it is just the largest building on the site, then the water would be adequate. This comes into play with the 13 and 13R question from before because this jurisdiction does not allow a reduction in site fire flow requirements when an NFPA 13R system is used. They only allow a 50% reduction when an NFPA 13 system is used.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[stookeyfpe]

Travis:

I couldn't find any amendments for fire flow on the City of Phoenix website. It must be some informal interpretation. They have the authority to make that determination per 2012 IFC Section 507.3.

 

[TravisMack]

It is in their published Fire Code. It is a 50% reduction for 13 and no other modifications. B105.2

https://codes.iccsafe.org/public/chapter/content/461/

If we base site fire flow on most demanding single building, the municipal supply can handle that. If we base site fire flow on all of the buildings on the site, then the site fire flow can not handle the demand. This would then require the 50% reduction allowed and drive everything to an NFPA 13 system.




Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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[cdafd]

One fire at a time/ one building?

Unless unusual buildings set up?

 

[TravisMack]

Yes. I have always gone by largest building. But, I wanted to just make sure. This has been an interesting project with all of the interpretations from everyone involved.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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[MGXFP]

Appendix B of the IFC generally references a single structure or portions of a structure that are separated by rated fire walls.

The ISO manual for fire flows also indicated the formulas are used for a single structure.

Generally speaking the principle is a single fire exists at any one time in the built environment.

Multiple fires simultaneously are generally a sign of natural disaster or arson.

 

[stookeyfpe]

Travis:

I wasn't able to read the amendment in the PHX Fire Code (apparently I need some off-brand reader).

If a jurisdiction adopts Appendix B of the IFC, Section B104.2 is applicable:

Portions of buildings which are separated by fire walls without openings, constructed in accordance with the International Building Code, are allowed to be considered as separate fire-flow calculation areas.

One can use a fire wall to establish the boundary for calculating the fire flow. The limitation is the wall can't have openings and that's hard to do an apartment building that may have different heights, areas and different construction classifications. It get's even messier because the IBC allows openings in fire walls, and in certain cases requires openings, i.e., Horizontal Exits.

In cases like this one strategy I employ is to emphasize that openings in fire walls is common in these "City In A Box" style of construction and that in podium construction, the IFC says nothing about penetrations (i.e., gravity waste chutes, plumbing piping, etc.) yet prescribes no penetrations in the horizontal plane. Radiant heat transfer is a function of distance and materials rather orientation. If corridor sprinklers aren't required you may be able to use these for equivalency. Of course, that get's messy if one building has open-ended corridors under the IBC and is designed to NFPA 13R (no sprinklers required depending on the corridor design) versus a building protected by a NFPA 13 sprinkler design.

I wish I could offer a better answer but it's the best I can do on an internet forum.

 

[TravisMack]

Scott:

We are using the largest building on site to determine the site fire flows. It turns out that a lot of this back end work was done, it had just "gotten lost" by others. You have to love how some of this plays out

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[stookeyfpe]

Travis:

We constantly preach and require that all of these details need to be documented. I'll state that this level of detail isn't required for a 5,000 square foot tenant finish out of a Donut-Taco Palace in a sprinklered strip center. But when it comes to large, mixed-occupancy, mixed-construction, and phased construction design, all of the basic design conditions must be agreed to up front. It gets even more complicated when the project involves hazardous materials or high-piled combustible storage.