Balcony Collapse in Berkley, CA 37

[MJB315]

See link:

http://www.latimes.com/local/lanow/la-me-berkeley-balcony-collapse-20150616-story.html#page=1

"We shape our buildings, thereafter they shape us." -WSC

 

[3DDave]

It looked to me like the detail put the flashing under the membrane and called for caulk to prevent water from funneling from the top of the flashing under the membrane. I think that one should never put an uphill-facing joint where water will drain. Membrane should have extended up the wall and under the door frame extrusion. If there is some requirement for metal flashing, that should go over the membrane so the gap faces downhill.

The rot seems to be maximum where the detail indicates the flashing would end. The lower balcony had some leakage but did not look rotted. Maybe the lower balcony had the flashing over the membrane; the membrane extended up the wall; the caulking was better for some reason; the upper balcony deflected the majority of water from that part of the lower balcony.

 

[RoopinderTara]

As a professional publication that covers engineering, design and architecture, I feel it is our duty to provide information to the public that provides an understanding of the possible causes of the failure so something like this can this can be avoided in the future. I am reaching out members of this forum to see if they would be able to write an article about the engineering aspects of the balcony collapse.
Requirements: Insightful, engineering analysis, 1200 words, minimum, 2 pictures, minimum. Need by: ASAP
Please reply back if you are available and interested. Any summary or thoughts on what you would like to develop in the article beyond what is suggested above would be appreciated. Also, do estimate how soon you could submit this article. With news stories, time is of the essence and we are already a little late with this one.
Roopinder Tara
Director of Content
ENGINEERING.com
rtara@engineering.com

 

[MacGruber22]

“It was definitely not large enough to be what the city would call an ‘open space balcony,’ where groups of people could stand outside,” said Carrie Olson, whose 14-year stint on the review committee termed out last year. “This was meant just to be a place where someone could stand out for bit, get a breath of fresh air. Not for something like 13 people.”

Well, that opinion makes me want to pull my hair out. Though, thank God their job title wasn't listed as building "engineer". We don't need more fuel to fan this fire:

http://www.eng-tips.com/viewthread.cfm?qid=180126

I look forward to reading the op-ed. Could you provide a link in this thread when it has been posted, RoopinderTara?


"It is imperative Cunth doesn't get his hands on those codes."

 

[hokie66]

RoopinderTara,
It would be irresponsible for any of us here to write the article you want. We can all speculate, and some things are obvious, but any detailed analysis of this collapse will have to be done by the investigators in Berkeley. In case one or more of our members are involved in the investigation, I think they will not be releasing a report any time soon.

 

[Ron]

hokie66....well stated.

 

[TXStructural]

What we generally find in investigations is that very few people (architects included) understand how water travels in building. They don't even seem to understand the two main principles of water usually-but-not-exclusively flowing downhill and humidity permeating any contained space. Repeatedly, balconies fail and walls rot because "that cut/tear/hole is not big enough to let _much_ water in..." The history of EIFS as one glaring example.

Someone mentioned the white deposits on the wood remnants. That is most likely salts coming out of the wood AND fungus byproducts, it is very commonly seen on wood that has been routinely or repeatedly wet.

 

[AUCE98]

Be curious to know what the condition of the other balconies on the top floor look like. It seems like from the photos above that the balcony which collapsed was shielding the one directly below, i.e. no signs of decay. Significant amount of roof run off, perhaps.

 

[1gibson]

Random thought, did previous occupants have potted plants out there that were watered daily?

 

[ChiefInspectorJeff]

Proposed new code:
Any wood structure exposed to the elements that is used as a deck, balcony,walkway,or any related purpose shall be constructed of pressure treated wood elements. If enclosed construction it is to be vented by an area of 1/180 s.f.of structure. Vents shall be removable for periodic inspections.

 

[theonlynamenottaken]

what do you think would be an appropriate code modification?

If a building code modification is in order then I had something in mind that is actually a combination of hokie66 and manstrom's ideas. Maybe something to the effect of:

EOR is to identify and designate any structure, or portion of a structure, that is determinate with respect to structural analysis and that is to be subjected to moisture, exterior exposure, or other conditions conducive of rot and degradation. EOR is to include these areas in the Special Inspection data for the structure. The responsible design professional shall ensure that these designated areas comply with one of the following:

a) The structural members and connections shall not be permanently concealed by architectural finishes and shall be left visible in their final, completed form.
b) Employ hatches, ports or similar devices in the concealing finishes to allow future inspections of structural members and connections.
c) Be designed for 200% of the loads set forth in ASCE 7-XX.​

However, I don't believe that code modifications are an effective way to address this issue. At the end of the day the people footing the bill for this collapse will be insurance. There would most likely be more real-world impact if insurance companies required inspections, offered rate discounts for inspections, or at the very least included some very specific smoking-gun questions in their application/questionnaire and seriously hike the rates depending on the answers. Changes won't happen until there is the threat of someone's wallet getting lighter...

 

[TXStructural]

I would also add that the EOR is usually not the right person to do envelope moisture control. That is the domain of the architect on most jobs.
At a previous employer, I investigated an entire school that was constructed such that the wall cavity held standing water, and in his wisdom, the architect had permitted (in writing) the builder to leave off the waterproofing on the exterior face of the wallboard behind the brick. It was so bad that the steel stud exterior framing was completed rusted through in many places. The entire exterior of the classrooms was removed - brick, stud wall, insulation - and replaced between the last day of spring semester and the first day of fall semester.

I am watching a cheap wood apartment complex going up near my house. (The structure is cheap, not the rent, based on what I see locally.) Not 20 minutes ago, I drove by and observed the balconies in various states of completion. 2x6 or 2x8 framing, a rim joist against the lap siding and/or EIFS, enclosed underneath with solid boards of reconstituted wood. Having watched the job go up from the recently cleared earth, including the spunbound polyolefin moisture barrier go on, I would lay odd that they will have water problems in short order. A lack of diligence in waterproofing is a pet peeve of mine. Shoddy construction costs us all a great deal.

(Now, if they had constructed it of reinforced concrete...;-)

 

[hokie66]

Amen, TX. Part of the problem is that architects have largely abdicated their primary responsibility of vapour and water proofing. They just make it the builder's responsibility, and many builders have no clue. However, many reinforced concrete structures have their problems with water as well. "Water is the greatest enemy of buildings". I forget who said it.

 

[ChiefInspectorJeff]

Here is a framing plan.

Inspector Jeff

 

[MacGruber22]

Looks like nearly a 1/1 back-span ratio. We certainly never go for that at my firm, regardless of how heavy-duty the uplift connectors are. Though, not sure how any of that really plays into the failure photos.

"It is imperative Cunth doesn't get his hands on those codes."

 

[Ron]

About 80 percent of the building failure investigations that I do have a root in poor waterproofing of the building envelope. I routinely see poor detailing and even worse construction. As I mentioned before, for wood framed balconies there is a need to provide drainage at the waterproofing plane of the concrete topping support. There is a nifty design for this using a device known as a "T-bar". It allows drainage at the waterproofing membrane plane and bleeds out the side of the balcony. The problem is that neither the architects nor the contractors seem to understand its function and routinely will specify a detail band around the balcony that the contractors will then proceed to construct incorrectly and block the drainage plane. In the past 4 major condominium envelope failures I've investigated all had similar issues. Fortunately none of them were cantilevered, so life safety was not an issue when found....but could have been in the future.

 

[Triangled]

ChiefInspectorJeff
Can you upload a clearer version of that structural plan?

 

[ajk1]

Even pressure treated wood has a limited life and will eventually rot. Galvanized steel connectors will eventually corrode. So yes p.t. wood should be used, but irrespective of that, there must be regularly scheduled inspections. Better yet, don't use cantilevered wood balconies.

About 20 years ago I had to recommend that all the cantilevered wood balconies on a 6 year old low rental housing be cut off due to rot found on some of them. I was a very unpopular person at the tenants's meeting called to explain the recommendation. However the recommendation was followed and they had no more balconies. Thank goodness.

 

[Jerehmy]

Having regular inspections sounds great, but this will never happen.

I'd be much more comfortable requiring stainless steel connectors and a higher preservative treatment. There are ones that last a lot longer than 20 years. Per AWPA U1 (Link), decks have a use category of 3B or 4A. They should increase it to 4C or even marine.

Per home depots website, pressure treated lumber has a chemical retention of 0.05 lb/ft3 using MCA. This seems low.

If you look at Table 15-5 in the wood handbook (Link), you can see that there are plenty of treatment options that will last longer than 20 years. Increasing the retention in most of the treatments resulted in NO failures after a substantial amount of time.

I'd rather have a certain level of preservative treatment and stainless connectors in conjunction with the inspections every so often.

 

[JAE]

Perhaps Hammurabi had a good idea. Use this law and the problem should take care of itself.

If a builder build a house for some one, and does not construct it properly, and the house which he built fall in and kill its owner, then that builder shall be put to death.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[manstrom]

Looking at the flashing detail in the article here, there is an expansion joint that allows water under the slab. The flashing should flow over the balcony, not under it.

http://www.berkeleyside.com/2015/06/19/no-smoking-gun-in-berkeley-balcony-design/

Regarding the backspan of the balcony beams and joists, 2:1 is best practice but not code required. The failure wasn't in the backspan lifting up, the beams and joists sheared off.


When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller