Story Above Grade Plane and item #2- 12' interpertation

[arch82]

Hello forum,
I am an Architect and would like to request a little feedback on this scenario:

Trying to correctly determine the number of stories for application of TABLE 504.4 ALLOWABLE NUMBER OF STORIES ABOVE GRADE PLANE
I am currently designing the building as TYPE VA & 4 stories but would much rather call it 3 stories and VB.
Currently no issues exist with the AHJ and frankly they are going to look to me to make the case.

Using 2020 NYSBC = 2018 IBC (looks to be the same language for definition)
[BG] STORY ABOVE GRADE PLANE. Any story having its finished floor surface entirely above grade plane, or in which the finished surface of the floor next above is:

1. More than 6 feet (1829 mm) above grade plane; or
2. More than 12 feet (3658 mm) above the finished ground level at any point.

My project : Wood frame on PC foundation
Floor 3 & Floor 2 -R2 Apartments
Floor 1 - R-2, S-2 parking, small amount of M.
Basement - utility/ storage and 10% of area will have a fitness room for apartment tenant use only.
The property is flat on two sides and clearly presents as 3 stories there. The other two sides are sloping including a main road. (-10' in 166')

The calculated average grade plane around the building is 6' or less meeting item #1.
The grade around 13% of the building perimeter (80' of 645') is more than 12' (12' to 16'). potentially(?) making it 4 stories if #2 is strictly applied.

A code commentary for this section (found on this forum and attached) seems to imply wiggle room on the item #2:
"Although the criteria for establishing the first story above grade plane in Item 2 indicates that such a condition occurs where the 12-foot (3658-mm) limitation is exceeded, the application of this provision is not that simple. It is not the intent of the code to classify a story that is completely below grade except for a small entrance ramp or loading dock as a story above grade plane, provided there is no adverse effect on fire department access and staging. An analysis of the impact of such limited elevation differences is necessary to more appropriately apply the code’s intended result"

If needed I can add retaining walls and build up the grade but would rather not for other reasons.
I realize it looks like an AHJ interpretation but they are a little weak in these gray areas and I am trying to get as much backup info as possible.

If it were to be strictly applied as a 4 story building would the VA (allowable by table 504.4) be required throughout or is there away to just apply it to the part of the building over the item #2 12'. (fire walls would not really be practical but possible)

The VA construction type while appearing easy looks like a potential minefield of details depending on who is looking at it. (Based on this forum)
No extensive information on this type seems available...

Thank you In advance.

Eric

 

[Tim Mailloux]

More than 12 feet (3658 mm) above the finished ground level AT ANY POINT seems pretty cut and dry to me. You have yourself a building with 4 stories above grade plane. FWIW I am going through the same exact thing on a school we have in design and I am stuck with IIA construction.

 

[Jay Smith]

A building with a concrete structure for the first story and wood framing above would usually be Type IA with a three-hour separation supporting three stories of Type VB, based on section 510.2.

 

[Paul Sweet]

I wonder whether changing "at any point" to "not over 5% (or some other reasonable %) of the perimeter" would make more sense.

When the building is on a hillside and all entrances need to be close to grade for handicap accessibility it's difficult to meet the 12 foot limit on non-residential construction.

 

[arch82]

Thank you, forum, for your inputs.

- I realize the "12' at any point" seems cut and dry but then the commentary suggests otherwise.
("They" say cmmentary it is not "code" but it is sold by the company that writes the code so how come it is not the code?.)

The commentary should be free to all and expanded to explain many of the obscure and convoluted code sections ICC has created and keeps changing every three years. You can not in my humble opinion restrict access to code/law related information/knowledge to only people with money. (end rant).

-I will have to revisit the podium concepts again but it is a wood floor above the basement with stairs and elevators penetrating so the 3 hour seems difficult
(I think it would not make financial sense to construct an elevated reinforced podium slab and supports (concrete columns/beams) in this (NY) region for the size project & only 3 stories (36 units).

I also notice that there is very little information (other than on this forum) as to what constitutes VA construction
(on the surface it seems easy but I see many minefields as highlighted on some of the posts I see)

Thank you again for the feed back

Eric

 

[bill1952]

("They" say cmmentary it is not "code" but it is sold by the company that writes the code so how come it is not the code?.)

The code is developed by concensus with many opportunities for public review and input and then adopted by legislative bodies. ICC does not write it. The commentary are opinions, I believe written largely by ICC staff, and not reviewed by public until after publication.

Recently the commentary was the basis for an unfavorable and inaccurate interpretation of a code section which was proposal I had submitted 15+ years ago. I challenged the interpretation and ICC issued a statement admitting the commentary was wrong, and of course they will correct it in the next edition.

So unless someone calls my attention to the commentary, I ignore it. But then I deal with some very specific sections which I have had a hand in developing, and understand why a generalist might find the commentary useful and beneficial.

 

[Jay Smith]

Moving up to Type VA construction isn’t bad. The unit separation walls, corridor walls and floor assemblies already had a fire rating requirement in VB. When you move up to VA it’s all the bearing walls, too. The gypsum board for the whole project will be 5/8” Type X and Type C gypsum board.

 

[arch82]

Bill- Thanks for the background on it.....I find the phrase "inaccurate interpretation" entertaining.

Jay- Yes thanks, I diving into requirements for bearing wall door jambs exterior, wall openings (jambs & sills?).
probably adding wood members for char time. penetrations by dryer/air ducts, etc. It all seems doable.

My local AHJ (very smart but not enough budget and training/support) will just give me a blank stare on these topics (rightly) expecting me to have it figured out.

If I reason with the AHJ a point suggested by the commentary and they accept my reasoning (even if it is flawed in other peoples opinion) than that
makes it an "accurate interpretation" v a potential "inaccurate interpretation". Not really a question but thinking to much.