automatic sprinkler system increase(s) 504.2 and 506.3
would anyone mind helping me understand what is meant in the code in 506.3 when it says there is a 200% (Is = 2) increase “for buildings with MORE THAN ONE STORY ABOVE GRADE PLANE” and 300% increase for “buildings WITH NO MORE THAN ONE STORY ABOVE GRADE PLANE”?
i have the 2015 commentary but it is too hard to try to use this since it has changed so much from 2012.
the language is a little convoluted by also i worked overseas and this definition of “story” trips me up since they handle this differently (not even going to try to explain since am so confused at the moment). i do understand i use the value (2 or 3) to plug into equation 52   i am just not sure which value i use on what sized/“story” buildings.
ALSO, i think someone was kind enough to allude to this on another thread i have here somewhere. BUT  once you run your Tabular Floor Area Increases using Equation 51 (with Is and If) you now have a NEW Tabular Floor Area Value which is larger but you have the (assume for a moment) SAME number of stories. so, if this was Type IIIA, 5 stories and 37,500 sf per story  maybe the floor area increase gets you to 50,000 sf per story.
at this point was the total allowable square footage (not a number with a variable or even apparently treated in chapter 5 2012?)  is it still the 5 stories x 37,500 sf per story? or does it increase to 5 stories x 50,000 sf per story i guess?
and then when you factor in 504.2 which gives you an additional story (you get this in ALL cases i guess irrespective of original number of stories)  you are increasing the number of allowable stories but you are restricted to the original allowable area PER floor (as a max per floor?) and you are restricted to the original TOTAL “allowable area” (in this case 50,000 sf x 5 stories).
do those make sense and if so would anyone mind stitching them up for me?
THANKS

Let me try to straighten this out for you, it's simple:
1) Table 503 is the Allowable Area Per Story. So, however many stories you are permitted to have in the building, including when you get to add one for a sprinkled building, each one can be as big as the number you are about to calculate.
2) To start, let's say Table 503 says that, per floor, you can have 10,000 SF. You also have a fully sprinkled building. So now we have to calculate how much more area the sprinkler system will allow us per floor.
3A) If your building is one story, you are permitted to add 3X the amount per Table 503 on top of the amount already indicated in Table 503  meaning this: 10,000 + [3(10,000)] = 40,000 SF/floor.
3B) If your building is more than one story, just change the 3 above to a 2. So you'd only get 30,000 SF/floor using the same equation.
4) Don't forget as well that you also get an increase for Open Perimeter Frontage. Won't get into that  not part of your question. Just know though that whatever you calculate from that also applies to the allowable area per floor.
That's really it, no need to think anything further about it. I promise you 100% that's how you go about this. I've done this over a hundred times in my office.

thanks a ton david.
so “no more then one story above grade” is a ground floor building /one story and “no more than two stories above grade plane” is a two story or more building.
on the TOTAL building square footage  in your example this would be 5 stories (for instance) x 40,000 sf per floor?
can i please ask about the /additional/ story you get by adding a sprinkler? would this mean 200,000 sf TOTAL but you get 6 stories instead of 5 (per 504.2)? i mean, you don’t get to add /another/ 40,000 sf when you add the additional floor  is that right?
THANK YOU 
1) Yes, "no more than one story above grade" is a ground floor building with a roof on top. No second floor. That is when you can apply the 300% rule. All other buildings  apply the 200% rule.
2) You are not correct on your added story thinking. If it's 40,000 SF total per floor, that number applies to however many stories you are allowed in the building, including the one you get to add because you're sprinkled. So, using your example, if Table 503 says that you can build a 5story building, but because you're sprinkled you get to add a 6th floor, you get 240,000 total GSF in the entire building @ 40,000 SF per floor.
Try to keep these two concepts separate, if that makes sense. If it helps, tackle the number of stories you're allowed first. Then figure out Allowable Area Per Floor and know that that number applies to the number of stories you calculated.

hey man. thanks a lot. i may have to figure out a better way to thank you than just saying "thank you".
can i just follow up here with the hopes that it is /also/ helpful to others at some point?
right now i only have the straight code (i got chapter 5 2012 from the library) the "prezi" presentation and the link benjaming just posted. and my 2015 commentary is no good for this. i have to review the last two but i have managed to scare up a 2010 CHING building construction illustrated at the library so i've xeroxed chapter 5.
this example is confusing me. can i ask you at /some/ point to take a look at it?
i see that the second two examples to the RIGHT appear to be simply showing "formal" examples that would be possible once you arrive at your CHOSEN building form per the Allowable Area (Aa) as they show on the left? is that right??
1. what is the top example? it is saying that given a hypothetical project with Group B, Type IIIA, 28,500 sf for At (Allowable Tabular Area per floor) [and 65'/5 stories per Table 503]  that IF YOU CHOSE TO MAKE IT 3 STORIES it would be 85,500 sf? i mean, what is the "3" where i put the red dot? you are allowed 5 stories but for some reason the client chose 3 stories and with this number of stories the buiding is 85,500 sf total area?
2. this example is assuming the /same/ 3 stories, applying the 506.2 Automatic Sprinkler System Allowance  and changing the At from 28,500 sf to 57,000 sf per the THREE STORY sprinkler increase (200% 506.2 increase)? then they are taking this 57,000 sf and saying  well, i guess since our /program/ says THREE stories we have are going to multiple this by 3 to get a total building area of 117,00 sf?
if so (and assuming i wanted to run a "maxed out" example)
A. 28,500 sf x 200% Is sprinkler increase for TWO STORY OR MORE building is 57,000 sf. Tabular Area Per Floor (At per 506.2)
B. five story allowable building (503) is 57,000 sf (At) x 5 (five stories) = 285,000 sf total building area
C. apply 504.2 Automatic Sprinkler System Increase and add 1 story at 57,000 sf to arrive at a total building area of 342,000 sf Total ALLOWABLE Building Area?
i know this is sort of in the "code weeds" but it would be super nice to know if i am on or off target with this if you get the head for it at some point. the example in Ching I find confusing and i am not sure that there are many examples to run since ASC, Ballast, Ching and everyone else seem to be showing chapter 5 2015 which has changed in a major way...
THANKS

Jonathan,
I've read all of this a few times now and am totally lost  no clue what you're asking here. I think you should simply learn how to use the tables, as I've described above, and that's it. If an example in this book sounds confusing, it's probably written poorly and is not going to serve you well. I've read it a few times  without me actually sitting there with the book in front me, it's hard for me to react to the images you posted.
The question that you'll get on the ARE regarding this will be straightforward. It will test your ability to identify the construction type and the use group of a building, and then use these tables to find out maximum building height and maximum area per floor. They'll tell you if it's sprinkled or not. Hope that helps  it will be simple enough to figure out if you just understand how to use these tables.

sorry. quick one here please? er, sort of quick.
way at the end 506.4 is area determination based upon building height (2 stories is Aa X 2 and 3 or more stories Aa X 3).
but earlier you determine Aa using Is from 506.3 of either Is = 2 for one story or Is = 3 for two or more stories.
this means you arrive at Aa (modified tabular area from 51) /before/ you get to 506.4.
so you have to decide how tall your building will be 1, 2, or 3 or more /before/ you get to 506.4 don’t you? well, actually i guess you just have to run the two Is values so you have a one story option but you can also calculate a two story or a three or more story option when you get to 506.4.
does that make sense?
i mean, it seems like you need to work a 1 story example in 506.3 (Is = 3) AND work an example with two or more stories (Is = 2) so that you can arrive at 506.4 to have a one story value (previously arrived at), a two story value (Aa X 2 per 506.4) and a three story value (Aa X 3 per 506.4).
does that make sense? i mean if you are looking to determine your formal options you have to run two Aa values and then run two 506.4 increase to have three formal examples:
1 story
2 story
3 or more stories. 
hi david,
just one point here that may have gotten lost in the shuffle of my questions (again THANKS for all the help).
506.3 lets you apply a /multiple/  for adding sprinklers  to your Tabular Area (At) by letting you multiply the tabular area by a sprinkler increase (Is) of either 2 for a two story building (Is=2) or by 3 for a one story building (Is = 3).
this effectively gives you 3 x At (the Tabular Area) when calculating your allowable per floor area (Aa). effectively when you look at equation 5  1 this gives you 4X the tabular area for a one story building [Aa = At + (3 X At] or it allows you 3X the Tabular Area for a two story building [Aa = At + (2 X At)].
but it is only when you get to 506.4.1 when you start looking at multiple story buildings three stories or beyond.
so (per 506.4.1)  in the case of a THREE story building you get the /full/ per floor area (Aa) for /each/ floor. but when you get to a fourth or a fifth floor your Total Allowable Building Area (i'm calling it Ab because the code has no variable for it) you are limited to a total allowable building area (Ab) of THREE times your per floor area (Aa).
so when you add the fourth or fifth story you have to effectively allocated the total allowable building area into the 3X per floor area for the Allowable Building Area.
basically you can have three stories at the full amount
or you can have two stories at the full amount and a third and fourth at half of the per floor area each
or five stories with the first two at the full per floor area and floors three through five as a total accounting for one per floor area.
you can slice it any way you need but the total never exceeds 3X per floor allowable area (or the total Allowable Building Area Ab) per 506.4.1.
total code work weed wacking but thought to mention it.

Jonathan, I'm going to add one more wrinkle. Your comment about the third and fourth floors being half, so that the total area is 3xAa applies when not sprinklered. 506.4.1 Exception 2 allows the maximum area to be maximum allowable area per floor times number of stories. So your sprinkler increase applies to all stories, not the 2 or 3 times for single occupancy multiple story buildings.
EDIT this doesn't appear to be supported by the commentary. It talks about allowing a residential to be higher, but doesn't really make "sense".

hey matthew
thanks a lot. i actually used my ICC membership today on this.
help me here?
i hope they adopt a designation for total allowable building area. it would make it a lot simpler.
also, the exceptions in some cases are hard to incorporate. they sort of read like double negatives.
what is 2 saying again please? say if we were thinking formally? it is saying what david said and i am missing? is it directly contradicting the earlier portion of that section of the code? i’d like to dig into it but it’s a bit dense (or at least i’m feeling that way) with that one.
THANKS 
i see. 506.4.1 applies globally to UN sprinklered buildings but if you have a sprinklered building where you’ve increased the At using Is  then you use exception 2 and it gives you /full/ floor area (Aa in the case where you may have had a frontage increase) for ALL allowable floors?

I'm reading the commentary now, and it makes it sound like what I'm saying is wrong. It gives an example with sprinkler, and still applies the 3x building allowable area. Something I've not had to deal with before, certainly a level of detail the exam hasn't gotten to either.
If it means anything, it looks like they've changed this as well in 2015. Seems like it would be the (At + NSxIf) x Stories (Sa), not the exceed 4 (so a 5 story building would still only allow 4 times the floor area).
Sa = Actual number of building stories above grade plane, not to exceed three. For buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.2, use the actual number of building stories above grade plane, not to exceed four. Just looked up 903.3.1.2, and that's for residential (NFPA 13R). So stick with 3x for max area.
Makes me wonder how high rise buildings work now...

/thanks/ matthew.
mind if i follow up with you briefly on this tomorrow?
i just ordered 2012 commentary because 2015 is useless for any of this.
also, unless i am mistaken, ALL versions of ching (2010/2012/2015) have bad typos on frontage increase. also, this 2012 ching page posted above (that i had to have someone send me) on the whole building area frontage sprinkler increase is at a minimum so schematic as to be almost impossible to follow.
at the same time if i review that exception 2 it does sort of sneak in a reference to 506.1 which may sort of throw a wrinkle in the wrinkle (as it were). but barring the commentary that exception is /almost/ a triple negative if it is an exception referencing a code section. that’s almost too hard to follow.
i /would/ like to leave a proper bread crumb trail if only for others that may come along later.
but that said, is it a fair question to ask how far into this one should get? Aa = At + (At x Is) + (At x If) and the If = (P/F  0.5) x W/30 with W being 30’ where all Wn are greater than 30’. or should one also be able to run the “W Weighted Average” where any W /under/ 20’ is NOT counted and any W /over/ 30’ is recorded as 30’? or presumably that last one is unlikely to be needed.
appreciate the help a great deal. apologies for the long winded posts but sort of killing two birds with one stone.
Please sign in to leave a comment.
Comments
16 comments