2012 BC Building Code – Illustrated Guide for Seismic Design of Houses

Here is a link to the reference document provided to describe the new seismic requirements for housing and small buildings, under Part 9 of the new 2012 BC Building Code.

One of the main difficulties occurs whenever our designs stray from a simple rectangular box shaped building as generally referenced in the guide, and what appears to be the basis for the new code language.

On the west coast of BC, many custom homes push architectural design to reflect wildly different forms and shapes, incorporating large open spaces and large glazed areas to enjoy the beautiful views.

It does not take long before these types of features limit our ability to satisfy the prescriptive requirements of Part 9. Once this happens, the entire structure must now be designed by a Structural Engineer under Part 4 of the BC Building Code; the same section that larger buildings are designed under which is inevitably more stringent in its requirements.

There is no argument that complete design by a structural engineer will result in a more robust and durable structure with respect to withstanding an earthquake. However, many people will be surprised with the additional costs required for the more comprehensive engineering services, in addition to the increased construction costs associated with satisfying the more stringent requirements of an engineered Part 4 structural design.

Closing Thoughts:

We can’t fault the code for making these initial steps to making single family housing better equipped to resist earthquakes. For years we have pushed the envelope in our designs under Part 9.

The goal posts are now set for what we can achieve under Part 9, however, in many instances the limits will not be indicative of the types of houses we are used to designing, building, and or living in; particularly here on the West Coast.

So, either we change our expectations and make compromises in our designs, or be prepared to pay more…

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