Seismic retrofitting…someday

This is pretty big on my “wish list,” but unfortunately keeps slipping down my “to do” list.  Although Portland is not as prone to severe earthquakes as parts of California, we do get them, and there is a known pattern of a catastrophic quake every 300 to 500 years in region.  Since our house is almost 100 years old, it was not built with any kind of earthquake engineering know-how.  Old houses with the mudsill just resting on the foundation are very susceptible to sliding off during a major quake.  Six months ago I got all worked up earthquakes, and we decided to just go ahead and hire someone to attach our house to the foundation.  Well, that is easier said than done, because I found that very few contractors specialize in this.  I had a very unsatisfying experience calling the one “seismic specialist” I could find (the call basically ended with us hanging up on each other – he was extremely rude).  By that time I had done enough research on the Internet that I was convinced that I could just do it myself, if necessary.  The only flaw with this plan is that it’s going to be awhile before I can get the job done.  We agreed to finish the upstairs first, although that would be quite an irony if our entire house collapsed in the meantime!

Once I get it bolted, I found that the insurance through our Farmer’s agent is really pretty cheap (about $300/yr).  The catch is that they won’t insure the house if it’s not bolted.  So it’s a real catch-22.  From what I’ve read, bolting is the single most important aspect of earthquake resistance, so the need for insurance is fairly low once you get the job done.  However, for $300, I’d sleep better having the insurance.  Also, who knows how good our 96 year old concrete really is?  There are many resources out there that explain retrofitting, but here’s a fairly good one put out by Simpson Strong-Tie.  Since we don’t have a cripple wall, we’ll have to use the UFP foundation plates to tie it down.

ufp.JPG

 

I’m hoping to start a dialogue with this post to get opinions and comments from other homeowners.  I’d like to hear what others have done (or not done).  I’d especially like to hear if anyone has good insurance advice or knows of reliable contractors that do this type of work.  While it’s not that complex, it does look like it’d be a good size job.  If I could find the right contractor, I might just go ahead to pay someone to accelerate this project by 6 months or more.

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22 thoughts on “Seismic retrofitting…someday

  1. Interesting post you’ve started here. First let me say whatever I say here is PURELY my opinion and in now way ENGINEERING ADVICE. I am a structural engineer but I’m not licensed in your state nor would I ever give professional advice here.

    Having said that your idea of simply bolting your 100 yr house down sounds good but in reality isn’t really going to do much for you. The reason I say that is fairly straight forward.

    Here’s the short simple answer. When an earth quake strikes it starts moving the ground and your house will want to follow. If you bold down the sill plate it’s going where ever the foundation goes. However, if the wall/sill plate connection is not strong enough all that will happen is the sill will separate from the wall.

    Think of it like this, each component from the foundation up to the roof will see “loading” due to the seismic event. Therefore, just attaching the sill plate is only one link in a long chain. Sorry if this isn’t the best news in the world I’m just trying to caution you that it’s not as simple as bolting down the sill plate. I’d be shocked if the insurance company found that acceptable.

    I have a feeling they would want to tie the sill plate to the wall and also make sure there is sufficient shear strength in the walls to transfer the loads.

    Best of luck and I’m eager to see others responses.

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  2. When we first moved back to Portland I asked my insrance provider (State Farm) about this too. The answer was the same; you can’t get earthquake insurance unless you retrofit the house with bracing. I didn’t ask specifically if the house just had to have the bracing, or if it had to be certified somehow or installed by a licensed contractor. That would be a good question to ask your agent. I asked “About how much should I expect to pay for this retrofit?” The answer was “several thousand”. I left it at that.

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  3. Thanks for the comments, guys. The way I see it, there are two main issues…structure and money. While I would really hate to see our house devastated in a quake, I don’t know that it’s truly feasible to “earthquake proof” this house, just as Todd said. There are many potential points of failure, and I just can’t see pulling off all our siding, adding plywood and other bracing to create shear walls and then re-siding our house. (I did consider doing this for about 15 minutes one day after I spent too much time looking at California quake damage on the internet).
    So, since a true retrofit is not going to happen, that brings us to the money part. Todd, while it may seem hard to believe, my insurance company only requires the bolts. My agent told me it was literally a checkbox on his screen (bolts: y/n). There was no requirement for verifying the integrity of the rest of the house. So, whether or not the bolts actually work, I can get covered. However, in most of the reading I’ve done, the bolts are strongly advocated by many municipal sources in earthquake-prone areas, even if no other upgrades are done (of course the reinforcement of cripple walls, if you have them, is also mandated). There are a variety of forces that different earthquake types can exert on a structure, so bolting alone may help with some and not with others. While I am also an engineer, I’m electrical and not mechanical, so I have to rely on my memories of classes I took 14 or 15 years ago!
    Anyway, although I hate to hear that our house could still end up in our basement or our yard, I really appreciate the input. And Joe, you expressed exactly what so many people here do (myself included). It’s so easy not to do the retrofitting, because no one knows when a major quake might hit. And there’s a good chance it won’t even be during our lifetimes. But given the crazy prices of real estate here lately, can you imagine what would happen if your house were destroyed? If you ever want to frighten yourself, Google “Cascadia Subduction Zone.” Oh well, pass me another beer!

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  4. According to the Simpson pdf you linked, houses without cripple walls need the UFP plates, shear angles and post caps. I don’t see how the materials could cost that much, and if you have an unfinished basement like I do the work should be fairly easy. Then call your insurance provider, have him check the appropriate box, and sleep better at night. Do you have a link to the cost of the Simpson stuff? Now you’ve got me interested. 😉

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  5. I don’t, but Home Depot/Lowe’s carries the parts. I’ve priced out the UFP plates before at about $10 or $11/each. Our basement was “semi-finished” when we bought the house, but after ripping everything apart for new plumbing and wiring, it’s a few steps down from unfinished. I can get access to all the areas I need to, but I’m not very excited about the crawlspace part. Oh, and I already bought a rotohammer for the project (back in December…), so I’m ready to go. We should do it like an Amish barn-raising. Get a few people together that need to do the same thing and go to town…

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  6. Julio – I’ve been following along your blog for the last several months. Neat stuff! I’m doing a complete renovation of my 1927 house in St Johns. Blowing off the long open room w/ knee walls on the second story and adding nearly full width shed dormers front and back to get an real complete second story. Anyway, I’m having to go through a structural engineer for the seismic and shear requirements for the city of Portland. I’m getting my plans from the engineer later this week. I’d be happy to pass along what I find out.

    From a previous conversation with the engineer he had mentioned having to bolt the structure to the foundation with a Simpson product, but I do not believe it is the same one as you are contemplating using. Apparently it is something more along the lines of the Titen HD, but attached to a double stud in the shear wall sections (possibly reinforced w/ 1/2″ plywood covering the expanse of shear wall)and some other Simpson product to attach the Titen to the double stud. If that is clear…

    Anywho, I’ll pass more along if you’re interested when I have the actual specifics.

    I’d like to pick your brain about running the ductwork in your house, if you don’t mind. I’d looked at contracting that out, but the bids I’m getting back on that particular service are not encouraging.

    – Mick

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  7. Mick,

    Yes, I’d appreciate learning what you find out from the city, and I’m sure others will, too. I am a total notice with the ductwork, but I’d be happy to share whatever might help…

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  8. Julio,

    Give enough notice and I’ll help with some labor, no problem.

    Mick,

    I haven’t blogged about it yet, but I installed a new furnace over the winter and had to deal with running some ductwork. I also have some HVAC experience, although it was on the controls side. I’d be happy to discuss.

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  9. Joe – Sounds fantastic. Here’s your 6-9 month notice. I still have to get this $%@^ upstairs project finished first!

    And sounds like you’re miles ahead of me in your HVAC knowledge, so I’ll let you handle that…

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  10. Hi All,

    Nice blog. I’m an architect here in Portland. I deal with upgrading the lateral strength of these older homes on a regular basis. Bolting the house to the foundation is absolutely a good thing to do. As Todd mentioned above, if we get The Big One in Portland, I’m afraid the additional bolting probably won’t help much. But chances are that if a moderately severe earthquke strikes, these bolts will help minimize any damage.

    Sometimes earthquakes (like the one we had several years ago) produce a wave that will move your house up and down as much as it does side to side. For some of these deeper earthqukes, the bolting could help a great deal. For others, not so much. It just depends on the type of earthquake and the configuration of your house.

    The cost of a non-invasive seismic upgrade is expensive considering what they actually do but next to smoke detectors and a thorough electrical inspection, it’s some of the best insurance you can buy.

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  11. DougS,

    Thanks so much for your comment – very helpful. You’re reaffirming my train of thought…bolt the house, get insurance, weather the moderate quakes and be covered in the event of The Big One. Sometimes I fantasize about building a new house with a massive, reinforced foundation and steel framing, but unfortunately I like these old houses too much.

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  12. I can’t believe I found your blog! I have been sitting here for over 2 hours Googling this topic trying to find answers. I am in the inspection period on a 1912 house on approximately SE 60th & Woodstock Blvd here in Portland. The home inspector told me I should get earthquake insurance on this house due to the age, which led to insurance company telling me the same thing they told you, then learning about retrofitting/seismic upgrading, which let to panic, which led to Google, which led to the Cascadia Subduction Zone, which led to an hours scanning Google results, which led to HERE. Keep me in the loop. I’m in on the barn raising, information sharing, bolt imbedding, information gathering, contractor group rate or what have you. I too would like to protect my $350K investment! I have 48 hours to make my final decision. I feel better knowing someone else out there is in my exact position. The City of Portland just had a brown bag related to this topic and I have a call into the Engineering Section Manager that presented there to find out if there are any contractors in the area and how I go about getting more information.

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  13. If you find any contractor info, we’d appreciate it. I’m still planning to do this myself, but I don’t want to keep putting it off forever. I am surprised that the issue is not more commonly discussed here in Portland and that there aren’t better resources to help people sort through this. It seems like a good niche that a contractor could get into…

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  14. Julio – So, I finally got my structural engineering documents. Everything is down at the city going through review. My situation for the seismic retrofitting may be slightly different and more involved than what you were envisioning for yourself. For mine I have to drill into the top of the basement foundation wall 10”. Epoxy a piece of threaded rod into the hole and attach it above to a double stud (running the full length top-to-bottom) in the wall cavity with a different Simpson product than you were looking at. The one that is spec’d is a PHD2-SDS3 (I can’t find a good image to embed into this post so you’ll have to do a search for it). These are installed in pairs, and they make a shear wall section, one installed at either end of the shearwall. Then the section is sheathed with ½” plywood inside and secured to the double studs with a wicked nailing pattern of anywhere from 3”-6” o.c. at the edge w/ an 8d nail. I’m trying not to tear off the siding on the outside of the house. I suppose as an unintended side effect I’ll never have to worry about tear-out when hanging something on the wall in sheetrock, it’ll be backed by the ply. I’ve got a fairly small house, the footprint is only about 700 sq ft, but like many older homes – lots of windows. So, I have 11 shearwall sections, which translates into 22 holes in the foundation. That wasn’t so bad – I rented a big rotohammer and a massive 36” long masonry bit. However, the Simpson hold-downs are spendy, I’ve been pricing them and it looks like it’ll be about $13 each. Then comes the real kicker, the rods have to be epoxied into place and the homeowner has to hire a third-party engineering company to come out and watch the rods being installed. He verifies that the holes are deep enough, are clean of all debris, and that the epoxy is mixed and installed correctly. My brother-in-law is a concrete guy and says that he’s typically seen that service go for about $250 for them to show up, and then $25 a hole. Of course the whole thing has to be permitted and so far that isn’t too bad for the remodel. As far as I know the seismic stuff is included in this for the city permit. There are several other things I have to do structurally for the remodel, but this is the extent of things that directly tie into the seismic stuff. Initially I started this as a necessary step to complete this remodel/addition, but I’ll sleep better in the years to come knowing that I’ve done what I could do in case we ever see a decent earthquake.

    Congrats on impending new baby. My wife is due in just under 3 weeks with our first. Good luck!

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  15. Mick,
    Your house should be in great shape by the time you’re done with it. That’s definitely the right way to do it.
    Interestingly, it seems that the city has good guidelines when it comes to structural renovations of a home, but they stay away from the business of permitting simple bolting projects. I know because I called and asked them about it. I had hoped to get it permitted in order to have good proof for the insurance company. However, the BDS person told me that they don’t offer permits for bolting, since they consider them an optional, voluntary project. They mentioned the same engineering company, suggesting that perhaps I could get them to “certify” the lack of dust in the holes in lieu of a permit.
    Anyway, I later called my agent and found out that they didn’t have any certification requirements (again, just the y/n box on the form), so that’s when I decided to skip the certification. Also, I will probably be doing mine in sections, so I won’t be in a position to let them inspect them all at once.
    Thanks for the great information, because obviously there are plenty of others out there with similar questions!

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  16. Dear Juilo,

    Thanks very much for your accounts and pictures (especially the kids) about retrofitting.

    I (with help from former neighbor) did some epoxy fastening and sheerwall additions to my 1901 home in ’94. Now I’m changing insurance and looking into current requirements.

    Could you give me a clue where to find the gas shutoff devices? I’ve called NW Natural…. Just got a call ‘Service Now’ and they can do the deed next week. Yea! Thanks again.

    Judy Litt

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  17. I just had a conversation with my insurance, Liberty Mutual, about this. Even though it’s true that coverage is fairly cheap (additional $300/yr), and they only require attachment to the foundation, there is a huge deductable- $40K-$50K. Although these older homes have already survived minor quakes, a moderate one might cost you a huge chunk that the insurance won’t even cover. I think it’s worth getting an experienced retrofitter to do the work and sign off on it, just for proof and resale value, who cares about insurance. The lady I spoke with seemed to think if a big one hit we’d all be waiting for government aid anyway. (Yikes, I’m not expecting there would be any handouts, especially if there’s no proof of having made a legitimate effort to secure one’s own home.) I’d just pay to do it right and consider insurance an afterthought.

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  18. I met with a guy who did quake retrofitting and consulting for corporations in CA, then moved to Portland and now works here. His advice for my 1920 NE PDX house was to not bother bolting to the foundation because of the concrete quality. It’s really coarse stuff, with pebbles, and he said it just wouldn’t hold in a large quake. It would just crumble around the bolts. He said concrete from before the mid-1930’s just isn’t strong enough to bother with. He did, however, suggest strengthening where the support posts connect to the main joists in the basement. Said that would help keep the house more intact, less prone to collapse.

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    1. I’ve been told the same thing regarding the lousy concrete. In my case I’d be doing it to satisfy the insurance requirement, not because I believe that it will make a difference with the “big one.”

      I see a comment or two below about the policies having large deductibles, which they do. However, I’d prefer to be facing a 40k deductible than the 3-400k to completely rebuild our house. Especially since we still have a mortgage that would need to be paid back regardless.

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