Code Definitions: Balcony vs Deck

[NW Architect]

The 1994-and-later UBCs have different live load requirements for residential balconies vs residential decks (See Table 16-A, line 12). SOMEWHERE in the code the two are defined. As I recall, a balcony is a cantelevered structure and a deck has supports under its outer edge. I cannot locate those definitions to save my life.

Where in the UBC are "balcony" and "deck" defined?

Are there similar distinctions in the IBC? Where are the IBC definitions found?

[Mark G]

Re: Code Definitions: Balcony vs Deck

In CA, which is based on the IBC, the definitions are at the beginning of the chapter on structural design, Chap 16, 1602.1. Hope that helps.

[stamcon]

Re: Code Definitions: Balcony vs Deck

In the 06 IBC, it's 1602.1 and your definition is basically what the IBC states.

steve

[Dick Seibert]

Re: Code Definitions: Balcony vs Deck

NW:

I did about an hour's searching and finally found something I didn't think I would find, so I'm giving all my research until eureka!

Hmmm, I know nothing about the I Codes, but the 97 UBC:
1006.3.2.1 General. An exterior exit balcony is one the components of the exit discharge. It is defined as a balcony, landing or porch projecting from a wall of a building and used for egress purposes.

Sec. 1602 (16-96-1 and 203-96-1). Definitions important for the use of Strength Design (LRFD) and ASD are provided. The proposed definitions are derived from the ASCE 7 standard, but have been modified as needed.

New definitions of "exterior balconies" and "decks," referred to in Table 16-A, will clarify the appropriate uniform loads to apply to these structures. This will facilitate uniformity of enforcement in live load design requirements for exterior balconies and decks. The definitions were located in Chapter 16 to clearly identify that these definitions apply to the load criteria and not to other provisions, such as exiting.

UCC Code Apps Chapter 16:

Q: Please differentiate between the loading criteria specified in Item 12 of Table 16-A as they relate to a residential exterior balcony and deck. Please address the rationale for the difference in the design loading.

A: The issue of determining the appropriate design live load for an exterior deck has been addressed in the past. The code has no size limitations for residential exterior balconies, and reviewing the dictionary definitions of "balcony" and "deck" does not provide much assistance. The American Society of Civil Engineers ASCE 7-88 document entitled Minimum Design Loads for Buildings and Other Structures has a table that is similar to UBC Table 16-A which specifies 60 pounds per square foot (2.87 kN/m2) for balconies. The ASCE table restricts a balcony designed for 60 pounds per square foot (2.87 kN/m2) to one that does not exceed 100 square feet (9.3 m2). This size criterion may be used by the building official to determine whether the 40- or 60-pound-per-square-foot (1.92 or 2.87 kN/m2) live load is appropriate for a specific structure.

The rationale for the higher design loading of small balconies is based on the potential of the smaller balconies being subject to a higher actual loaded condition. Therefore, a residential exterior balcony could be described as a residential structure of a size where a higher load is likely to occur.

UBC Code Apps Chapter 5

Q: Does Exception 1 to Section 509.2 allow 36-inch-high (914 mm) guardrails for outside decks and balconies in residential occupancies?

In Group R, Division 3 and Group U, Division 1 Occupancies, outside decks and balconies are permitted to have 36-inch-high (914 mm) guardrails. In Group R, Division 1 Occupancies, only the interior of individual dwelling units and guest rooms are permitted to have 36-inch-high (914 mm) guardrails. Outside decks and balconies of Group R, Division 1 Occupancies are required to maintain the 42-inch (1067 mm) height requirement.


UBC Chapter 4:

405.2 Guardrails. All unenclosed floor and roof openings, open and glazed sides of stairways, landings and ramps, balconies or porches that are more than 30 inches (762 mm) above grade or floor below, and roofs used for other than service of the building shall be protected by a guardrail.

UBC Dhapter 2:

SECTION 203 - B
BALCONY is that portion of the seating space of an assembly room, the lowest part of which is raised 4 feet (1219 mm) or more above the level of the main floor and shall include the area providing access to the seating area or serving only as a foyer.

BALCONY, EXTERIOR EXIT. See Section 1006.3.

UBC Handbook Chapter 14

The requirements of Section 1402.3 are intended to protect wood members used in the framing of balconies and landings from dry rot. Where the balcony or landing is sealed underneath, water and moisture are not allowed to dissipate, and dry rot is the eventual result. These areas should have a minimum slope of 1/4 unit vertical in 12 units horizontal (2% slope) to help ensure adequate drainage.

UBC Handbook Chapter 32

SECTION 3204 - BALCONIES, SUN-CONTROL
DEVICES AND APPENDAGES

The code permits the projection of balconies, unroofed porches and the other items listed in this section above a height of 8 feet (2438 mm) in accordance with Figure 3204-1. The intent of the code is that no projection should be permitted near the sidewalk level and up to 8 feet (2438 mm) in height so that free passage of pedestrians along the sidewalk will not be inhibited.

Above the 8-foot (2438 mm) height, projections are permitted as long as they do not interfere with public utilities. It is generally assumed that utility lines for telephone and power will not occupy this zone except for the service entrances to the buildings. There are jurisdictions that have high-voltage power lines running along the sidewalk, and the regulations of the agency that regulates the power companies generally require certain clearances from these lines. Therefore, in addition to the requirements shown in Figure 3204-1, power-line clearances should also be checked, and the requirements of the National Electrical Coder should be checked when it is adopted by the jurisdiction.

UBC Dhapter 11

1106.2.3 Changes in level. Changes in level of not more than 1/2 inch (12.7mm) in height shall comply with CABO/ANSI A117.1.
Changes in level greater than 1/2 inch (12.7 mm) in height shall be accomplished by a ramp, elevator or wheelchair lift complying with CABO/ANSI A117.1.

EXCEPTION: Where exterior deck, patio or balcony surface materials are impervious, the finished exterior impervious surface shall be 4 inches (102 mm) maximum below the finished floor level of the adjacent interior spaces of the dwelling unit.

UBC Dhapter 16 HA HA!

SECTION 1602 - DEFINITIONS

BALCONY, EXTERIOR, is an exterior floor system projecting from a structure and supported by that structure, with no additional independent supports.

DECK is an exterior floor system supported on at least two opposing sides by an adjoining structure and/or posts, piers, or other independent supports.

My bill will be in the mail.

[NW Architect]

Re: Code Definitions: Balcony vs Deck

God Bless ya' Ricardo. THOSE are the definitions I remember having been shown once upon a time BUT I'm staring at Section 1602 - DEFINITIONS of a 1994 UBC and the only things defined are Dead Load, Live load, and Load Duration - nothing defining decks and balconies. Weird, huh? I sense one of those major re-formats that dropped things through the cracks. So I check 1991 UBC, but no structural sections - they were printed separately. (I've got UBCs back to the 1960's - but they all are published without the Structural sections. GAAAAAHHH!!!!)


So, Dick, before you close out your timesheet, in what edition of the UBC did you find the above?


Stamcon, IBC 1602. Got it! And thanks, I got frustrated NOT finding it in UBC and just punted on the IBC. Appreciate the lift up.

Where would we be without the internet and this forum??? You guys (and gals) are the best!

[Dick Seibert]

Re: Code Definitions: Balcony vs Deck

That's the '97 UBC.

[NW Architect]

Re: Code Definitions: Balcony vs Deck

Dick,

Reread your post . . . 1997 UBC. 10-4

But, like a mongrel with a bone, I couldn't let this go.

It would seem that the FIRST appearance of the deck and balcony definitions occurred in 1997 UBC. As stated above, the definitions do not appear in Chapter 16 of the 1994 UBC. So I looked at my 1991 and 1988 UBCs a bit more closely. Those were editions PRE-renumbering. The structural stuff in those editions appeared in chapter 23, and the Definitions had only the three definitions I list for 1994, in the post above. Tables 23-A, in those editions, however, DID NOT have different live load requirements for Residential decks vs Residential balconies.

SO I CONCLUDE, that the renumbering of 1994, meant to be just a renumbering to get all the chapter numbers of all the then-extant model codes to be the same, ALSO INCLUDED some subtle changes. The live load business being one of them. So, in 1994, until amended at some point, or until rewritten in 1997, the UBC had different live load requirements for residential decks and balconies - that were things undefined.

TA-DAH! Entertain with THAT tidbit at your next cocktail party!!!!

[NW Architect]

Re: Code Definitions: Balcony vs Deck

Oh what the hell. I pulled out my 1952 UBC. Section 2301 has definitions only for Dead Load and Live Load. Table 23-A has the good ol' 40psf live load for "Dwellings" and "Hotels"

I kinda liked the requirement for the structural design:
"Sec 2303 Any system or method of construction to be used shall admit of a rational analysis in accordance with well established principles of mechanics"

(And, no, there's no typos there. What the eff does "shall admit of" mean???)

[Dick Seibert]

Re: Code Definitions: Balcony vs Deck

NW:

I think "shall admit of a rational analysis" means that the building official is required to accept "a rational analysis in accordance with well established principles of mechanics", meaning that the BO has to accept the design professional's analysis, and can't require the 60#.

I've always thought that Chapter 16 should have been incorporated into Chapter 23 so we all would know what was going on, not put Chapter 16 into another volume which is only purchased by engineers. I even wonder how many architects actually buy Volume 2?

It's my understanding that the IRC completely disregards decks, even with the well publicized deck collapses.