Regarding moisture and building envelopes, maybe it’s time to repost this, a presentation I erroneously poo-pooed before giving it a fair shake when it was first shown to me by way of this site. This one’s worth making the time for, in my opinion…maybe watch it over lunch, or something. It’s Joseph Lstiburek’s lecture at, ironically enough, Berkley. Link
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Based on their observations, city staff recommended that the Berkeley City Council adopt new and modified regulations to enhance the safety of all current and future buildings in Berkeley.
The recommended changes would make new balconies and other sealed areas that are exposed to weather subject to stricter requirements on materials, inspection and ventilation. The proposed rules would also require regular maintenance inspections for all such spaces for future and existing buildings.
"I'm going to propose, similar to San Francisco, owners get a structural engineer to inspect the buildings every five years," Eric Angstadt, director of Berkeley's Planning and Development Department, said at a press conference Tuesday.
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If the balcony was indeed 4ftx6ft as stated somewhere above and the code in force at the time of construction required 60psf design live load, then the balcony was in fact overloaded at the time of the failure if there were 13 people on it as reported in some of the articles linked above, since 4x6x60/13 = 110lbs per person and people weigh more than 110 lbs.
It is interesting to note that the 2012 IBC, currently in effect in many locations, has reduced the balcony live load to "same as occupancy served", which for multifamily buildings like this one, is 40psf for private rooms. The 2006 IBC required 100 psf for balconies serving private rooms of multifamily buildings like this one and allowed the use of 60psf for balconies serving 1 and 2 family dwellings if the balcony was less than 100sf. This reduction from 100psf to 40 psf was quite significant and unconservative in my opinion, and I will not be surprised to see it revert back to 100psf in future editions of IBC. Does anyone know what is required by 2015 IBC on this?
Nevertheless, from the photo posted above, it seems rather obvious that the cantilevered joists were pretty deteriorated from rot caused by water infiltrating into the building envelope and that rot was a significant contributing factor to the collapse of the balcony.
Several of the comments calling for requiring regular inspections seem well intentioned and sound good politically, but a meaningful inspection of this type of construction would be impossible since the framing is all concealed within the building envelope.
does anyone believe that the gypcrete was placed at 2% slope per plan and that it might had inadequate slope or even the wrong way? water test might have been useful to see if water actually drains off the balcony.
I agree with gte447f. I am all for supplementary reviews, however, a meaningful review would include dismantling the architectural finishes which is rarely done during periodic visual structural reviews. Perhaps for critical components, the architectural finishes would have to be thought out in advance with access ports or other such removable panels.
wouldn't a city stipulation imposed upon owners for a sealed engineering survey of balconies every so often, say 5 years as proposed in article, or maybe yearly for 1st five years, make owners think twice about wanting balconies and cause them to require architects to design system facilitating simple routine structural observations?
"Perhaps Hammurabi had a good idea. Use this law and the problem should take care of itself.
Quote (Hammurabi)
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."
Not really, since it's often more than just a single factor that causes these things; a lazy, or malevolent, owner is not exactly a rare thing.
As for inspections, that's just going to be another tax that will jack up the cost of living. I'm forced to do a backflow valve test every year, which is $25, so not that bad, but a structural exam is going to cost $200?
TTFN
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IRstuff - over time all those lazy, malevolent owners will be killed since their balconies would have all fallen and killed someone.
We'd be left with diligent, nice owners.
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faq731-376
1. Periodic inspections would not solve a hidden problem like this. They would just create, as Irstuff said, another tax.
2. Failures rarely occur due to overloading, they occur due to defects. So changing code live loading will have little effect.
3. The statement above that the flashing should have been turned out above the topping slab is wrong. The topping slab is for protection of the membrane, not to serve as such.
(Despite the somewhat unclear plans photo, I will weight in on what seems to be a problem so designers will avoid it.)
That drawing seems to show a saw cut top chord of the cantilever lumber. This would probably change the grading of the lumber and if pressure treated, would remove the treated wood and open it up to moisture intrusion. It also opens up endgrain right at the area where the flashing most likely leaks at the face of wall.
The slab doesn't protect the membrane, which stops a large distance before the wall. In fact, it stops just about where the wood rotted. The slab does serve to funnel water that runs down the wall directly to the open edge of the membrane. Had the membrane been continued and terminated under the door sill above the concrete, there would be no opportunity for water to get under the membrane and from there to the wood.
3. The statement above that the flashing should have been turned out above the topping slab is wrong. The topping slab is for protection of the membrane, not to serve as such.
Here's what I'm looking at - in the first I've exaggerated the positions; I think the filler board will eventually get compressed, and not rebound, leaving a gap and with it a reservoir of water. In any case, it cannot form a bond with the concrete, so water will bypass it and be directed as shown, with the first place it contacts the wood in the offset of the barrier where the moisture barrier doesn't exactly follow the flashing, leaving at least a small reservoir of water that cannot evaporate, but will be consumed by fungus to drive rotting.
The next shows the moisture barrier under the metal flashing, protecting the potentially exposed portion of the barrier. The barrier is continuous and water is prevented from contacting the wood, while being able to be absorbed and evaporated through the concrete.
Some details are omitted from both images - the filler board, the caulk, and the door details.
