When the Big One hits, what kind of damage can you expect? While it’s up to fate as to how intense or severe the quake will be — or when it will happen — the fact is set in stone. Earthquakes can and do happen here.
In fact, Washington state is second only to California when it comes to earthquake risk, and this is reflected in our earthquake classifications.
Earthquake classifications assign a numerical value to a building based on construction features affecting its ability to withstand an earthquake. Unlike building codes, earthquake classifications are based on potential property loss, not life safety. From a property insurance perspective, they predict how specific building materials should perform in terms of loss.
When evaluating a risk for earthquake coverage, there are many factors to consider, including distance to fault, soil type, liquefaction and of course, construction materials. Here’s a quick guide to the construction component, along with some common exceptions and miscategorizations.
Earthquake Classifications Quick Reference Guide
Exceptions and common mis-categorizations
- Load-bearing tilt-up concrete construction is 5AA, not 4C.
- All-metal buildings with combustible sheathing and/or insulation are 2A or 2B, not 1C or 1D.
- Interior finish does not affect earthquake classification.
- All-metal buildings should be Class 2, not Class 3, regardless of size or type of steel supports.
- Steel Frame Buildings with non-load-bearing reinforced concrete panel walls are classified 3B or 3C, not 5AA.
- Buildings with metal stud walls and wood truss roofs are classed as 5C. Structures which are classified as wood frame but have concrete supported floors and/or some walls of unit masonry or concrete are excluded.
- Basement walls are generally excluded unless the basement is partially buried and considered a story.
- Brick and stone veneers do not affect a building’s EQ classification.
Related: PropertyEDGE Hazards video tutorial
Of course, construction materials are just one part of the equation. Where the structure is built can have a huge effect on its potential for earthquake damage, a topic we dive into more closely in our Soil Liquefaction, Earthquakes and Underwriting and Life in the Ring of Fire blog posts.
In the meantime, you can use our PropertyEDGE tool to dive into your specific earthquake risks, or visit Washington’s Department of Natural Resources Earthquakes and Faults page to learn more about risks from earthquakes, volcanoes, tsunamis, and other natural disasters.
“Editor’s Note: This post was originally published in June 5, 2013 and has been updated for freshness, accuracy and comprehensiveness.