Tag: The Really Big One

Home Earthquake Vulnerabilities: Hillside Home Recommendations

Home and building owners, as well as renters, in hillside neighborhoods need accurate information about their earthquake risk so they can make informed decisions.

Hillside homes can have high, even catastrophic, earthquake risk. The previous two posts discussed common geological and structural problems with hillside homes.

But if you live in or own a hillside home, what should you do? Move away? Just live with the risk, and hope “The Really Big One” doesn’t happen in your lifetime? Get the house seismically upgraded? Get more information?

Yes, those are the four options that come to my mind:

1. Move Away?

I’ll address this first, because many reading this are concerned about earthquake risk. Of those of you who own and/or live in a hillside home, I’m guessing a high percentage of you didn’t know how dangerous this type of home can be in an earthquake. It’s likely no one told you anything about earthquakes when you bought or moved into the house, in fact, it may not have even entered your mind at the time. But here you are, and now you are thinking of moving, perhaps.

Moving away makes sense if:

  • You are confident the house is dangerous, and
  • You’re confident that it would be too expensive for your budget to fix, and/or
  • You aren’t too attached to the home, or maybe you don’t even like it.

Moving out of a hillside home that you perceive to be dangerous makes more sense, in my opinion, than staying and living with the risk. But you may want to consider my last point (#4 below) before moving.

2. Keep the house and live with the risk?

I certainly don’t recommend this. But there are some situations that are less risky than others.

If you own multiple homes and are rarely occupying the house, risk (at least life-safety risk) is obviously lessened simply due to the fact that you aren’t around much. If you don’t have kids and travel often, that’s a similar situation.

If you have a family, especially with a spouse or kids staying home during the day, you genuinely could be putting their lives at risk by not addressing potential seismic vulnerabilities in the place where most of their time is spent.

If your house is looming over your neighbor’s house down the hill, they could be at risk also due to your home’s earthquake vulnerabilities. You may both have earthquake insurance policies (unlikely), but that can’t make up for loss of life. Just something else to think about before you decide to do nothing.

Interestingly, there may be an economic argument against doing nothing also. Suppose your hillside home is worth a million dollars. Let’s say the chance of a severe earthquake affecting this house in the next 50 years is 20 percent (this is in the ballpark of what seismologists have estimated). Suppose the odds of collapse of the home during the earthquake are 50 percent (arbitrary number), with severe damage likely even if it does not collapse. A retrofit costing in the tens of thousands of dollars, or even $100,000, isn’t necessarily unreasonable in this circumstance, for those with the available capital and desire to keep the home.

There are situations where a retrofit could be more costly, but this would be difficult to know without more information (which is why I like Option #4 below).

It’s also possible that the house has low risk of seismic damage. In that case, it may be reasonable to live with the risk. But how would you know this? You probably need a specific assessment to be sure.

A collapsed California house after the Northridge Earthquake. This will likely happen to some hillside homes in Oregon and Washington when we get our “Big One”. Please take a look at this picture and ponder if you are okay living with this risk before choosing to do so.

3. Have your home seismically upgraded?

Of course, I recommend a seismic upgrade for many hillside homes. I’m concerned about the risk of a Cascadia Megaquake, and what it will do to hillside neighborhoods. This is why I’m writing this and specializing in this type of work.

But the choice to upgrade the home has to work economically. Hillside home seismic upgrades can be expensive, and not only does the money need to be there to pay for the upgrade, but the benefit should be worth the cost to the homeowner. I recommend spending the time necessary up front so you have a good ballpark figure of the cost.

Don’t Mess Around With Cascadia

I strongly believe in conservatism with seismic upgrades. Our Cascadia Subduction Zone could produce a magnitude 9.0+ earthquake that could last 3 to 5 minutes. This earthquake will last much longer than earthquakes that have caused the collapse of hillside homes in California in recent decades. Homes that have poor seismic force resisting systems (such as stilts with wood bracing) could degrade with each cycle of ground shaking, and there could be hundreds of cycles in this type of earthquake.

My point is this: if you are going to do an upgrade, do something that will actually work. Don’t just pay someone a few hundred bucks to take a quick look at your house and give you a few cheap recommendations. Count the cost ahead of time and be willing to pay for the thorough upgrade that you really want, that will really do what it needs to do when the ground shakes longer than an average pop song.

Hillside home seismic upgrades are complex, and involve much more than just “attaching the home to the foundation”.

You will need a structural engineer who specializes in hillside building seismic upgrades. I’m trying to be that guy because there’s a need there, but if you find someone else who qualifies, that’s great! More engineers need to be doing this, in fact, we really need an “army” of specialty engineers and contractors retrofitting homes and buildings ahead of the earthquake who are passionate about this kind of life-saving work.

You will, in many cases, need a geotechnical engineer also. Geological risks can’t be ignored and can sometimes drive the cost of seismic rehabilitation through the roof. If landslide risk is high, mitigation may be expensive or even virtually impossible. Make sure you figure this out with a geotechnical investigation, and make sure their recommendations are followed in the seismic upgrade. Or, if landslide risk is apparently low, at least have a structural engineer consider slope stability in the seismic upgrade including a conservative design with a new foundation if needed.

A stepped foundation collector I designed for a hillside home built in 2001. The intent of this design is to prevent the stepped shear wall failure (described in the previous blog post) by directing seismic loads into the high part of the foundation. I communicated to the homeowner that this type of failure was unlikely for her house, but I couldn’t rule it out. She wanted to strengthen the house. I believe it was a reasonable decision that gave her house a “belt and suspenders”- i.e. some redundancy, to help her and her family sleep better at night.

Hillside Retrofit Economics

Some hillside homes are almost beyond hope of an adequate seismic retrofit due to high landslide risk or a combination of structural problems. It is possible that effective strengthening measures could cost in the hundreds of thousands of dollars if the owner wants to really mitigate their slope stability or significant structural weaknesses. There is little benefit to retrofitting a home structurally if the ground it sits on is unstable.

The earthquake risk of hillside homes varies significantly from house to house and from site to site, and the cost of a necessary seismic retrofit can vary from $0 (no retrofit necessary) to extremely expensive. The decision to upgrade, move away, or live with the risk is a personal decision based on life-safety concerns, risk tolerance, and personal economics.

Due to the variability of cost and the many factors affecting the seismic risk of hillside homes, there is a need for good, up-front information for hillside homeowners.

4. Get More Information.

I hope the information in these blog posts about hillside homes is helpful for making decisions. Since the information is not house-specific, however, many need to go a step further.

Consulting a structural and/or geotechnical engineer is appropriate, and I am happy to do this. My preferred approach is to use a developed seismic risk assessment methodology. I currently use FEMA P-50, P-58, and ASCE 41, depending on the situation. You can learn more about these assessments here.

I believe seismic risk assessments have great value, and are a good first step in the decision process. If you hire me for an assessment, you will get a structural engineer’s opinion (a qualitative assessment) as well as an analytical (quantitative) assessment. This first-pass information can be done quickly at a relatively low cost, to help develop the “big picture” of what a potential retrofit would look like and what the potential benefits are.

“FEMA P-50” is a good seismic methodology that applies to most hillside homes. It will grade the house (with a letter grade from A to D-) based on how well it will perform in our largest expected earthquake. When I assess a home this way, I develop retrofit concepts and then grade the house pre-retrofit and post-retrofit. Sometimes I will provide a “lean” retrofit option, in addition to a more thorough retrofit option, if that makes sense for the particular structure.

Even if your hillside home was engineered relatively recently, it doesn’t hurt to have it double-checked. Engineers make mistakes sometimes, and hillside home retrofits can be difficult to design correctly.

If you’ve read all three of my blog posts on hillside homes, you can hopefully tell that I’m trying to sound the alarm regarding earthquake risk with these types of homes. However, not all hillside homes are in danger.

My main point is that there are many variables to seismic risk with these unique structures. To make an informed decision about what to do, hillside homeowners need accurate information that takes all these variables into account. This information may lead you in many different directions depending on your specific house and personal situation.

For more information about seismic risk assessments and retrofitting, please see the Cascadia Risk Solutions website.

How to Cure Earthquake Anxiety

The reality of a potential impending large earthquake in the Pacific Northwest has made its way to the general public in the last few years.  When the New Yorker article “The Really Big One” came out in the summer of 2015, many of us were shocked and genuinely scared.  After some initial shock wore off, people reacted in a number of ways ranging from buying earthquake insurance to storing up food and water to just living with a new level of anxiety they hadn’t known before (the latter probably being the most common reaction).  I recall talking to an insurance agent soon afterward and he told me that it was crazy how many people had rushed to buy earthquake insurance recently.  He didn’t miss a beat transitioning to sales mode in his next statement, which was something like, “you should consider buying some also to protect your family.”

But what should we actually do with this information that is new to many of us? And, to address the title of this blog post, how do we deal with “earthquake anxiety”?

Consider this goofy story as an anxiety illustration:  I was recently in a restroom at Starbucks and the lock on the door didn’t give me any evidence that it worked. This mattered because the door opened to a view of the coffee line and cash register. I played with the lock and couldn’t gain any confidence in it.  It made almost no sound when I pressed it, and it didn’t seem to even change position. Opening and closing the door a couple of times didn’t verify it’s functionality, except for a small, barely audible click. I reluctantly used the restroom anyway, but not without some anxiety.

That’s already too much information with the personal restroom story.  But here’s the point about anxiety: it is caused by feeling like you have no control over a potential problem.  The solution, I believe, is a combination of taking purposeful action that addresses the problem and letting go of control over the things you don’t have control over.

Consider how much lower my anxiety in the restroom would have been if the door had a deadbolt that made a loud noise as it was being engaged and it visibly could be seen sliding into place through the crack in the door. In the same way, adequate earthquake preparedness steps give you confidence that you have addressed the problem and will likely survive “the really big one”, and even thrive in the aftermath and be able to help others.

I just mentioned that the solution to earthquake anxiety is to take purposeful action that addresses the problem and to let go of control over things you don’t have control over.  The first step involves practical actions, many of which could be accomplished by anyone living in the Pacific Northwest.  The second is more related to mental health, psychology, etc, which I’m not an expert on (but see Matthew 6:25-34 if you are inclined as I am to address this through the lens of faith).

I will dive into some specifics in further posts, mainly related to actions we can take, but for now I want to point out that we can only do what we can do.  We can’t control when an earthquake (or any future high stress event) will come, but we can make a huge difference in our resilience when it does.  A head-in-the-sand approach is irrational and will not make anxiety go away.  Also, resigning to the overwhelm of tasks ahead is not a good approach, either: “I’m not going to do anything because there would be too much to do”, or “it will happen if it happens” are examples of this kind of thinking.

The work ahead in earthquake resilience can indeed be overwhelming, but even just a first few steps can make a big difference on an individual or family level than not being prepared at all.  A good preparedness plan will add redundancy to whatever plans you put in place.  This is a topic, that, if you plan to live in the northwest for a long time, is very important.  What should your next steps be in 2017 to make yourself and your family more earthquake resilient? If you have no ideas, stay tuned here…