Seisemology Matters…

So, I grew up in the midwest. I built houses in the midwest. But if you want to build much of anything in California, the seismic aspect out here is a huge factor. I was discussing the shear transfer wall that our engineer specified on our plans in the last post, but I wanted to talk about some of the hardware that holds the wall down to the foundation.

Anyone who has build as much as a simple deck probably knows what a joist hanger looks like. They are pretty basic.

Simpson1It’s nothing more than a metal “U” that allows you to support a piece of lumber where it meets another. I think most everyone is familiar. If you are really interested in construction connectors, check out the Simpson or USP sites sometime. IF you are a construction geek at all, your geek cred will go way, way up.

So the companies that make joist hangers make a whole bunch of other products for all kinds of applications. The basic stuff you can pick up at nearly any big box or hardware store. The first thing I needed were a pair of SSTB anchor bolts.


These are just a 28-inch long, 7/8-in diameter bolt that gets embedded 24-inches into concrete to hold the wall down. Luckily, they sell these babies at Home Depot out here because they get used fairly regularly. Mostly for holding down houses, but also for beating the ever-loving crap out of somebody that owes you money. (Just guessing.)

On top of the anchor bolt a U shaped hold down gets bolted down to hold the wall in place. The hold downs I needed aren’t stocked though. Bummer.

However, I did get lucky. I just happened to be doing some recon work at HD to see what they had in stock and figure out what I was going to need to special order or get from my lumberyard. As I’m digging through the bins for these SSTB anchor bolts, I come across a beat up HDU8 hold down. Exactly what I need! I search the shelves for it and realize that this is not a stock item and must have been returned to the store and then simply tossed in a bin with other construction connectors. So I take my bolt and hold down to the register and whattayaknow, no SKU or price.

The clerk does some digging in the computer POS system and can’t find anything. So, in an effort to finish the sale and get to the customers behind me, she just overrides the system and sells me the items for $5.95 each. Score! That was like $70 dollars worth of hardware for $12.

For the other one, I just used Amazon. (Who’d have thunk it? What can’t you get on Amazon. And with free shipping via Prime, why drive to the store?)

OK, so now I have the wall poured, which you can read about here.

The shear wall gets framed like any other wall, only instead of 2 x 4s at the ends, it gets Douglas fir 4 x 4s instead. That was so these suckers had something to connect to:


Nothing says “don’t go” like twenty 1/4-inch screws and a 7/8-in bolt.

And the other end.

Still need to install all the screws in this one...

Still need to install all the screws in this one…

And, just in case you were concerned about the wall moving in the middle — have no fear!

IMG_0795One of these 6-inch screws goes through the bottom plate and into the structure below every 8 inches on center.

Wow. I swear by the end of this I could get a job with the USGS.

2 responses to “Seisemology Matters…

  1. Who knew that you would become a seismologist? You sure aren’t in Kansas anymore Toto.
    Nice work and thanks for the continued updates. We look forward to seeing it in person at Thanksgiving.


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