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Stories above grade plane...

R

Robert

Registered User
Joined
Jan 29, 2016
Messages
341
Location
Pinole, CA
Greetings...I hope everyone is staying healthy. I'm working on a fire rebuild (CA) of a tennis club, unsprinkled, complete rebuild. I am considering analyzing the whole building as an A3 occupancy rather than mixed use, separated. The ground level (locker rooms, pump room and office) is mostly subterranean. According to definition, it is not a basement but considered a story, but is NOT above grade plane. The floor above it is a story and is above grade plane. Am I correct that Table 504.4 will allow this: A3, unsprinklered, V-B) since the table is for "stories above grade plane" only? (assuming the area limitations have been met). Thank you.
 
How is it not a basement by definition?

Is the story next above more than 6 feet above the grade plane, or is the story next above more than 12 feet above the ground level at any point?

If it's neither of these two, then it is a basement by definition. If one of these does apply, then that level is a story above grade plane, and the story above it is the second story.
 
So how many sq ft??

Occupant load??

And you feel it does not need fire sprinklers?
 
Thanks. RLGA, yes, it is a story by definition because the floor above is 6' above grade plane. The definition for "story" is more than 6' above grade plane for more than 50% of the building perimeter. This is my condition. The definition for "story above grade plane" is more than 6' above grade plane for the entire building. This is not my condition. It's an important difference because table 504.4 is for the allowable number of stories above grade plane (and not the number of stories). So it is a 2 story building but only one of the stories is above grade plane. And if only 1 story is above grade plane, the table appears to allow the 2 story building for A3 occupancy unsprinkled. Your thoughts?

CDA...as far as I can tell, no sprinklers because building is less than 12000 sq. ft. and OL less than 300.
 
A tennis club and no drinking or eating?

Does the """ The ground level (locker rooms, pump room and office) is mostly subterranean.""" Meet 903.2.11 specific buildings, not to require fire sprinklers?
 
Since it is not a basement, it is a “story above grade plane” by definition and is included in the number of “stories above grade plane” when determining height per Table 504.4.
 
A little off topic, but just a note. As always Ron's graphic is spot on. The point that is often overlooked is the B dimension with underground parking. The problem that sometimes occurs is that the elevation of the ramp at the face of the building exceeds 12' and technically makes the underground parking the first story, always be sure to check the ramp. Just a random thought.

Ken
 
Thank you. I'm getting hung up on the verbiage for the definition of story which states "more than 50% of the perimeter". Ron. in your graphic, are you stating that if the floor above is 6' above grade plane at any point, or is it for at least 50% of the building perimeter? In my case, it is less than 50% of the perimeter, which is why I thought it is a story (rather than a story above grade plane). Maybe it is a basement? CDA, no food or drink...only an employee break room and kitchen. I'm getting close to 1500 sq. ft for the lower level so thanks for pointing out 903.2.11
 
Robert said:
...are you stating that if the floor above is 6' above grade plane at any point, or is it for at least 50% of the building perimeter?
Click to expand...
Note that the definition refers to grade plane and not finished grade. The grade plane will always be parallel with the floor, so you cannot have a story that is only 50% above the grade plane. Refer to the definition of grade plane in Chapter 2 to see how to determine the grade plane for your building. If you have a sloping site, then the grade plane may be above the finished grade on one side of your building and below the finished grade on the other side of your building--just like my diagram shows.

A story is considered either a story above grade plane or basement--there is no in-between.
 
Understood about the horizontal grade plane parallel to floor and the A dimension in your graphic. I'm not saying the story is 50% above grade plane, I'm saying that if the floor above is 6' above the grade plane around at least 50% of the perimeter of the building, then it is a story above grade plane. If less, it is a basement. Depending on where you cut your section around the building perimeter, the grade plane will be different (greater or less than 6' from the floor above). If it is 6' at any point around the perimeter of the building, then is it a story above grade plane? If so, what the heck is the 50% verbiage all about? I can cut sections all around my building and only find one spot that the floor above grade plane is greater than 6'. This is where I think the 50% comes in....
 
Maybe provide a sketch of your situation, because I don’t understand how a floor can be partially (i.e., 50%) above the grade plane—if one part is 6 feet above, then the entire floor must be 6 feet above.
 
My sketch would look just like your graphic, except that if I take the section in one part of the site, the "A" dimension is less than 6', while in another part of the site, the "A" dimension would be greater than 6' (the topography of the site). This is where I believe the 50% comes in under the definition....if the grade plane around 50% of the perimeter (where the sections are taken) is greater then 6', it is a story above grade plane. If less then 6', it is a basement. This takes the topography into account.
 
There is no 50% in the definition—I have no idea where that is coming from. The grade plane is the grade plane...it is set at one elevation. Topography only factors in when determining the grade plane. Once the grade plane elevation is determined, the floor next above is either at 6 feet or above, or it’s below 6 feet. No matter where you measure the distance between the floor and the grade plane, it will always be the same.
 
Having a simple mind and being lazy, I typically will take "spot" elevations around the building (or 6' off), add them up and divide by the number of elevations took, this should give you the "Grade plane". Note, as Ron mentioned, this will give you one constant elevation.

Ken
 
khsmith...yes, that's what I was seeking...the perimeter spot elevations need to be taken around the building, then averaging them to determine the A dimension. O.K. I feel better. Ron thanks for hanging in there with me. I do use your book but is at the office which is presently closed due to the virus. I am attaching a screenshot from the online 2019 cbc showing the 50% I was referencing to (at the bottom of definition of story)
...my screenshot didn't catch all of the definition. Anyway, I don't know where the 50% applies. Thanks for the help.
 
steveray said:
Watch for the windowless story stuff in Ch9 that also may drive sprinklers...
Click to expand...

Yes. As it turns out, after getting the grade plane correct, this lower floor is a basement. It does have an entrance into the locker room at grade, in addition to windows on one side. There are no parts of the basement greater than 75' from openings. However in section 903.2.11.1.3 (CBC), it states if walls or partitions block the hose streams, sprinklers must be installed. Does this apply where there is an entry into the basement from the exterior?
 
Sounds like it.....

[F] 903.2.11.1.3 Basements. Where any portion of a
basement is located more than 75 feet (22 860 mm)
from openings required by Section 903.2.11.1, or
where walls, partitions or other obstructions are
installed that restrict the application of water from
hose streams, the basement shall be equipped
throughout with an approved automatic sprinkler
system.
 
I'm wondering if that requirement applies to basements that have no exterior access (internal stairs only), so they would have to maneuver their hoses through windows, then the walls/partitions etc would be a major factor. Otherwise any basement with a single partition installed, would require sprinklers. Thoughts?
 
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