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NFPA #13 2013 Edition and composite wood joist construction in a hotel

NFPA #13 2013 Edition and composite wood joist construction in a hotel

NFPA #13 2013 Edition and composite wood joist construction in a hotel

(OP)
NFPA #13 2013 Edition and composite wood joist construction in a hotel

What I have is a four story motel with a sprinkler system designed per NFPA #13 because the architect took some trade offs in distances to exits and drawings are clearly marked NFPA #13.

We have 16" deep composite wood joists on all floors.

I've never had to deal with composite wood joists in a NFPA #13 system so I just want to make sure I understand this correctly.

If I am reading it right my design area has to be a minimum of 3,000 sq ft but the density would be reduced to .05 gpm over light hazard areas. Over ordinary hazard areas the design area would remain 3,000 sq ft but of course the density would increase appropriately.

Where this will impact the most is the first floor where we have a rather large lobby, a dining room and several meeting rooms.

I can not apply the quick response reduction for ceilings <20'. I am pretty much stuck at .05/3,000.

My question is what about the rooms on the second and third floor? The fourth floor has a conventional attic that will have sprinklers so the fourth floor is straight forward.

Second and third floor are mostly rooms and corridor but we will have an occasional janitorial space. The corridors themselves appear to have standard 2"x8" wood joists with drywall attached above a suspended ceiling so there appears to be nothing special here except for the rooms and what little janitorial spaces we have.

The way I understand it so far is the rooms themselves are treated as standard NFPA #13 dwelling spaces where I can use residential sprinkles but in accordance with the listing or a density of .10 whichever is more. As I understand it the reasoning behind this is the rooms themselves are compartmentalized and firestopped. Am I correct in this thinking or am I missing something?

I know, Google is my friend so I will start looking but I was wondering what the group here would have to say about it.

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

Let me try to break this down a bit. You are doing 3000 sq ft because you don't meet the criteria to exclude protection of the concealed combustible space without the design area penalty. As such, you have to do areas adjacent to the space. This includes areas above, below and to the sides.

I am doing this from memory, so I apologize if some is off, but I think I am going to be close.

1 - Using residential sprinklers, I believe there is an exception in 2013 or maybe 2016 that allows you do increase from 4 residential sprinklers to 8 for your calculation area.

2 - Please don't get confused on that 3000 sq ft penalty. It is to be applied AFTER all other modifications. So, you can not reduce to less than 3000 sq ft, even if you have 10' ceilings.

3 - In light hazard, you are "sliding up the curve" to get to 0.07 gpm / sq ft, not 0.05 that you mention. Look at the curves for OH1 and OH2 as appropriate for your areas.

In light hazard, may I suggest using 4.2k sprinklers. 158 sq ft at 0.07 gpm / sq ft gets you 7 psi. 5.6K sprinklers are 7 psi at 211 sq ft. You will be over-discharging most likely with 5.6k sprinklers in your light hazard areas. You are already dealing with a large design area, so you may as well do all you can to cut down the excess flow.

Now, assuming this is the framing for Level 02, 03 and 04, with standard roof trusses in the attic, you will have your 3000 sq ft pendent sprinkler design area on Level 01-04. The attic can be whatever is required per NFPA 13 for the construction type and slopes and sprinklers.

As far as using residential sprinklers in an NFPA 13 project, you can take advantage of some options to help out. Typically, you are dealing with small rooms per the definition in Chapter 3. Therefore, you apply the 0.10 density by taking the area of the room divided by the number of sprinklers in the room. You then compare that to the listing of the sprinkler for the spacing. Lets say you have a room that is 260 sq ft and you have 2 4.9k sprinklers located at 10' off the wall. The area per sprinkler for the 0.1 density is 130 sq ft or 13 gpm. However, you are 10' off the wall for each sprinkler. 20' spacing for a 4.9k pendent is 20 gpm. So you calculate those two sprinklers at 20 gpm each since the listing at 20' spacing is greater than the req'd density. Now, let's say you have this same room and only 1 sprinkler. Now the minimum flow is 26 gpm (260 * 0.1). This is greater than the listing so you must use that value.

Hopefully all of that helps to clarify. You could say I have done one or two of these smile. As always, you can call me if you need any additional help on this.

Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

(OP)
Travis, Yeah... I was going on the .05 from memory which isn't so good. .07 it is.

So on the second floor, almost all of which is rooms or corridor, I am still looking at 3,000 sq ft?

I never liked composite wood joists.

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

Yes. Unless you meet the requirement that the TJI are blocked into 160 ft3 (going off memory)volumes, then yes, you need to do the 3000 sq ft on any area that is adjacent to the TJI space.

Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

(OP)
Except for the corridors it appears everything is TJI space.

Yes, but the standard appears to be very specific as to blocking. how it is done and there's nothing on the drawings indicating anything of the sort. It's one of those drawings that leave lots to the imagination. Without a fire pump I am looking at some pretty good size pipe. Specs call for everything to be schedule 40 of course.

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

I'll offer one minor comment and it concerns protection of the concealed space. Travis Mack suggested the use of K 4.2 sprinklers. One consideration is if your protecting a combustible concealed space - AND - your design will utilize a dry pipe system, I have had issues arise because the designer failed to consider the pipe material requirement in NFPA 13, Section 8.3.4.4. That's all I have on this subject.

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

SprinklerDesigner2 - Everything Travis laid out is right on the money. As are you, when you say you are looking at some pretty good size pipe.

I'll only add one minor things to Travis's excellent post:

13-13 23.4.4.6.2 allows you to omit sprinklers in closets, washrooms and similar small compartments from your calculation when the design area is at least 1500 sq. ft. It's not uncommon to have 30+ heads in a light hazard calc in this scenario, so every head you can drop out of the calc helps.

I just submitted an extremely large NFPA 13 seniors home, all framed with TJI's, and a static pressure of 48 psi at the street. Quite a bit of 4" in light hazard on that one...

RE: NFPA #13 2013 Edition and composite wood joist construction in a hotel

Yes. I forgot the washrooms, closets and other similar compartments when shooting that out from memory. As soon I read it here, the light kicked on.

For the 4.2k sprinklers, I was assuming those would be on a wet pipe system feeding the ceiling sprinklers. 4.2k in a dry system doesn't work unless you have internally galvanized.

Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

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