So, why did the balcony collapse?
The building was built in 2006, therefore the 2003 International Building Code applies. The balcony was on the 5th floor and not the 4th floor as indicated. We know that portions at least of the whole building are wood frame. After viewing this photo: Berkeley Balcony Collapse Photo, you will see that this balcony is on the fifth floor of a mixed use / mixed occupancy commercial building. As the entire building is required to be built to the most stringent occupancy classification of a mixed type, which would be type B for business or type M for mercantile, this building cannot be built out of wood frame construction (which it appears to be) and you cannot mix building types.
The fifth floor balcony fell on the fourth floor balcony because of water intrusion due to missing flashings, (wall abutment and fenestration flashing at the door sill, or what is called a pan), both of which are required. These missing required flashings caused the wood to rot as water intrusion is evident.
This is why we have building codes but for some reason perhaps to save money some people don’t think it is necessary to comply. Yet others in professional fields choose to turn a blind eye. Too bad because these deaths are a direct result of poor construction and even poorer code enforcement. Gross negligence comes to mind.
The Building Code prohibits wood frame construction in excess of three stories in height. The Architect, Engineer, Contractor, Building Official, Building Inspectors and Plans Examiners are all required to know the building code.
Wood frame decks need to be roofed with a required wall abutment flashing. The door needed to have a flashing pan under it. The ends of the joists / trusses are required to be blocked over the wall and clearly are not. These are just first observations.
Whenever I opine I insert the Code References or Authoritative Documents for all to see and read for them, as an opinion without support is of no value and has no basis in fact. In other words, cutting and pasting is what gives an opinion authority and relevance.
International Building Code:
CONVENTIONAL LIGHT-FRAME CONSTRUCTION
2308.2 Limitations. Buildings are permitted to be constructed in accordance with the provisions of conventional light-frame construction, subject to the following limitations, and to further limitations of Sections 2308.11 and 2308.12. 1. Buildings shall be limited to a maximum of three stories above grade plane. For the purposes of this section, for buildings assigned to Seismic Design Category D or E, cripple stud walls shall be considered to be a story.
1403.2 Weather protection. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in Section 1405.4. The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water resistive barrier behind the exterior veneer, as described in Section 1404.2, and a means for draining water that enters the assembly to the exterior. Protection against condensation in the exterior wall assembly shall be provided in accordance with Section 1405.3.
1403.3 Structural. Exterior walls, and the associated openings, shall be designed and constructed to resist safely the superimposed loads required by Chapter 16.
1405.4 Flashing. Flashing shall be installed in such a manner so as to prevent moisture from entering the wall or to redirect it to the exterior. Flashing shall be installed at the perimeters of exterior door and window assemblies, penetrations and terminations of exterior wall assemblies, exterior wall intersections with roofs, chimneys, porches, decks, balconies and similar projections and at built-in gutters and similar locations where moisture could enter the wall. Flashing with projecting flanges shall be installed on both sides and the ends of copings, under sills and continuously above projecting trim.
If you read the exception and follow the ASCE you will not find that this building qualifies, either protected or non protected for any exemptions to the above Codes. A home inspector who knows construction practices, should know that you cannot construct a building in this manner. Additionally this balcony is an “area of refuge” meaning you have to follow the floor design criteria for dead and live loading that applies to fire escapes as that is what an area of refuge is in this case. You are not allowed to reduce the load per the formula for this type of structure in the code. Looking at the photos you can tell that the deck extended one half the length of the 3’ door leaf on each side. That makes the deck 9 feet long. Given that a guard rail in this type of structure, also supported by furniture heights in other photos, is a minimum of 42” high. Looking at the photos you can see that the balcony extended out nearly 5 feet. That would make the area 45 square feet in size. Area of refuge loads are required to be 100 lbs. per square foot in design and are not allowed to be reduced. That means the balcony had to be designed to meet a 4,500 lb. load. 13 people would have to weight 347 lbs. average each to exceed this load. A person is considered taking up 3 square feet when standing. Which means you can fit 15 people on this deck. Two more could have been added.
One could build a 1,000 story building out of wood and although it would work (rational analysis) it does not make it right. Building Code is a minimum code. It is the absolute least you can do. The wood may have been fine if it hadn’t rotted due to the absence of the required flashings and pan, a Building Code Violation. Every home Inspector worth his salt knows where all the required areas of flashing are required. If he does not, may I suggest a different profession.
So what caused the collapse based on preliminary observations and photo evidence? Water intrusion at the door sill and wall abutment which rotted the structural members. There is no flashing present at the wall or sill. Now look at the photos closely and you will see that the deck below has water staining coming out from under the perimeter drip edge flashing indicating that the same condition is present on the deck below. The upper deck would have received more water than the lower deck as the upper deck was acting as a roof. The lower deck now being more exposed which will accelerate deterioration resulting in catastrophic failure of that deck too. Again; after calculating the deck size and loads, the thirteen people weighed less than the required design load, probably by one half. This failure is a direct result of missing required flashing on a deck which should not have even been wood due to the height and building classification and occupancy.
In addition, the stucco or EIFS system is not installed per ASTM 1063 as required weep screeds and expansion joints are missing. This may have contributed to the water intrusion.