Monday, June 29, 2015


In a recent article I wrote about the effects Airbnb and other short term rental websites create on the construction industry. In a nutshell, I suggested that these short-term rentals are taking regular-long term rental units off the market, because landlords, home owners and many other "short-term rental managers" are using regular long-term units for short term rentals. This creates two effects.

One; the need for more long term rental units, i.e. more apartment buildings, and there is a boom in multi-unit entitlements and construction, which is great for us design professionals. Two; cities losing money because of the lack of collecting hefty hotel or transient taxes. And you know money talks.

I did not think action would be taken so fast.

Case in point, recently the city of Santa Monica outlawed short-term rentals of less than 30 days, period. The effects of this, of course, are yet to be seen. Proponents of home renting state that enforcing such a law will be extremely difficult and instead of forbidding a very lucrative money making opportunity in this "sharing economy" a compromise should have been made.

I don't think this is the end of this story. I think people will find a way around this "obstacle", but it highlights the challenge cities will face as they try to impose traditional regulations on a fast evolving industry. It may be a short sighted old method of trying to deal with a new world digital technology. I think it is under estimated, how quickly this digital world can adjust. As they say: "Follow the money..."


Okay, we live in Hollywood and everyone’s a film critic. Including me. SO, I would to write a few words about the movie that just hit the theaters "San Andreas". Many of you know that I'm a "young" (ha-ha-ha...) father again with two little creatures (one 3 years old and the other 4 months old) to take care of, which leaves me no time at all to go to the movies. In fact I have not been to the movies over the past 3 years, but this was a movie I had to see for obvious reasons. I design structures for earthquakes and I wanted to see what will happen to my buildings when the dreaded San Andreas hits.

So I went to see the movie. Well, I got far more than I was asking for and I’m now considering a move to Riggins, Idaho.I knew that a disaster movie has to have improbable scenes, breathtaking visual effects to keep people on the edge of their seats. I remember similar movies from the 70’s like the "Poseidon Adventure", "The Towering Inferno" and many others. But I think this was a little bit over the top.

Why? For several reasons.

Can a large, devastating earthquake happen at any time along the San Andreas Fault? Yes of course it can and it will as I’ve warned many times before. It is not the "if" but the "when" we have to ponder. Can it be a 9.3 or 9.5 as it is in this movie? No. By seismologist experts the San Andreas is capable of producing an earthquake in the magnitude of 8.3 to 8.5 max.

Can the San Andreas produce a canyon like the one in the movie, almost as big as the Grand Canyon? Not really. The San Andreas is a fault line where tectonic plates, like the Pacific plate and the North American plate, are moving side by side, parallel to each other not perpendicular to each other. Trenches may be created by earth collapsing on the surface, but very insignificant in size.

Can the San Andreas produce a tsunami at all? Very unlikely. The San Andreas is mostly on land and earthquakes created on land do not produce tsunamis. Tsunamis are created when an earthquake happens under the ocean floor and the ocean floor is moving up and down. This is not the case with the San Andreas, because this is a vertical fault moving only horizontally, roughly north and south, not vertically, up and down. Of course it can have some vertical component, seismologists do not know everything about the San Andreas, but a tsunami is very unlikely. The tsunami in the movie made the parting of the Red Sea from the Bible look like a kid's wading pool.

Can a tsunami, by the San Andreas or any other earthquake, create waves that crash onto the Golden Gate Bridge’s roadway, which is roughly 250 feet above the water level? The answer is a resounding no, because a really big tsunami is "only" about 30-50 feet high. Also in the movie this tsunami comes in like a big cresting, surfing wave which would not happen. Tsunamis come in like a rising sea wall of water. Remember the gruesome video footage of the Indonesian earthquake-created tsunami about 10 years ago, or the more recent devastating Fukushima earthquake-created tsunami.

Can a large earthquake created by the San Andreas cause this type of devastation with so many skyscrapers collapsing? Not at all. The movie exaggerates the scale of destruction, especially for tall buildings. Recently designed modern high rises are less likely to collapse. They will sway, some of them 10-15 feet at the top, but not collapse. We are going to have pockets of destruction, pockets of collapse and causalities, but it's not going to be an Armageddon. The toppling of buildings is very rare.

So what is the moral of the story? The movie is a good reminder that we live in earthquake country and we have to live our normal happy life, but we have to be prepared for the "Big One" (and for the smaller ones too). Earthquake retrofitting of vulnerable buildings is a must and earthquake preparedness should be taken very seriously. And when the San Andreas is awakened, then structural engineers will have a lot of work to do. As in the parting scene in the movie, the wife, Carla Gugino asks: "What do we do now?" Our hero of the movie Dwayne Johnson answers: "We start rebuilding our life" ... and we will need a lot of structural engineers... Dwayne, call me.


I assume everybody has seen in the news of the tragic accident that happened in Berkeley, where a balcony of an apartment building broke and fell to the ground killing six people. Indescribable tragedy, which I'm sure will be followed by lawsuits. But who is really to blame?

Preliminary reports say that the balcony, supported by the cantilevered floor joist, was designed properly. The code requires that balconies be designed for a "live load" supporting people, at 60 lbs./sq.ft. -- 50% more than floor loads of the same floor. Then what was the problem? Structural engineers visiting the site and looking at photographs said there were clear signs that the joists supporting the decks had rotted due to water exposure by the phenomena called "dry rot".

Dry rot is a condition of wood in which a fungus breaks down the wood fibers and renders the wood weak and brittle. Excess moisture is the root cause of dry rot. Dry rot is often confused with termite damage, because it is similar in appearance. Termite damage is, of course, visible by live termite galleries, termites swarming, termite droppings and it happens mostly in dry wood. In the case of balconies, the most likely scenario was that the waterproofing at or under the balcony door was insufficient, allowing moisture to penetrate this area and causing dry rot.

Is this avoidable? During my illustrious career I've been involved in numerous construction defect lawsuits -- mostly as an expert witness and not an engineer being sued. The majority of these lawsuits involved water leaking claims and damages caused by dry rot. Of course if a window is leaking and causing wood damage by dry rot, is not life threatening. It is a completely different situation with decks and balconies.

There were incidents in Santa Barbara and San Francisco before, where decks collapsed due to dry rot damage, injuring and killing people. Is there a way to avoid this? Yes and this is what I propose.

Everybody knows that if you build a flower bed you use pressure treated wood or "green wood" (not to be confused with the phrase "going green in construction" which is so popular these days). Pressure treating is a process that forces a preservative deep into wood products, preventing moisture from penetrating. These days there are no more "green wood" products, because the chemical used before is not "chromatid copper arsenate", but a less toxic borate based material. There are some other safer products as well. Arsenic is of course very toxic. (Do you remember the play by Joseph Kesselring, "Arsenic and Old Lace"?) Needless to say this process makes the wood quite unappetizing to all vermin, insects and fungus. So what am I saying with this? If pressure treated wood is more resistant to dry rot why not use it in construction in areas where it is more likely to get in contact with moisture? If Noah's Ark was made from this stuff, it would still be cruising the Mediterranean!

So, let's update the building code to use pressure treated wood products for all decks, bridges, balconies and similar areas, where potential damage by dry rot, termites, etc. can cause accidents injuring, or killing, people. It’s a safer, simpler, inexpensive way of construction!