One day — when is anybody's guess — a major earthquake will hit Washington state. When it does, what kind of property damage can you expect?
We can't predict the severity of the quake itself, but we can help you better understand how individual properties will hold up during an earthquake. That information is captured in a building's earthquake classification, a numerical value assigned 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
These buildings in Seattle likely have different earthquake classifications.
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 mis-categorizations.
Earthquake Classifications for Buildings 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 only partially below grade so is considered a story.
- Brick and stone veneers do not affect a building’s earthquake classification; however, there may be an additional premium if the veneer is covered under the policy.
You'll find the earthquake classification for buildings WSRB has inspected in our commercial property reports. When you look at the classifications, remember that they're just one part of the equation. Multiple factors affect a property's potential for earthquake damage. Learn more about them in our blog post, and get data on these factors in our new Earthquake Risk tool. Just login to try it.
Robert Lacy, WSRB's Vice President, Inspection Services & Professional Development, oversees our team of commercial property analysts as they produce advisory loss costs, commercial property reports and evaluate automatic fire sprinkler systems. He is involved in the annual evaluation of our loss cost levels and ensuring we are current on coding and rating issues for commercial property. He also works to encourage continual professional development for all WSRB employees.