Seismic Retrofit - How to decide between more L70 or less L90?

Question

Location: San Francisco Bay Area

Our house does not have a cripple wall. Plan A provides both L70 and L90 as options for floor connectors. Using L70 will require more work since we need to install more plates. Why would one want to go with L70?

Answer 1

L70 and L90 are both L-shaped reinforcement plates. The number simply indicates their length in tenths of inches.

• An L70 is 7" long
• An L90 is 9" long

That's it.

They match up to common dimensional lumber sizes of 2x8 = 7-1/4" wide and 2x10 = 9-1/4" wide.

For L90 to be useful, the lumber they are tying would need to be at least 9" wide. If it is narrower (i.e. is the common "2x8" size), the 9" strip will not fit.

Obviously an L90 has 9/7 of the strapping power of an L70.

Since it sounds like you're into scrimping and shaving on your earthquake compliance, remember -- the purpose of those "slumlord" government minimums is to prevent fatalities when the building gets totaled. That's what the government is hoping for, because that means they get a brand new building built to modern codes, LEED and all that stuff... all very happy numbers on their spreadsheet.

Whereas you have different risks. Your risk is of being homeless. You might think "Pish, get a hotel room. There are loads of those 99% of the time, what are the chances of an earthquake happening the same day as a national championship sporting event?" Except 100,000 other people may have the same problem as you. Or you might also think "So what, hunker down and wait for the FEMA money train to arrive." But that has not worked well for others who counted on it. And the Federal government has a very ... Federal ... perception of the value of a house.

From the mortgage lender's perspective, most of the value of a Bay Area single-family home is the land it stands on, so they still want the note payments.

So I say the best bet is to go in whole-hog with earthquake retrofits, with the aim of having the building be usable afterwards.