Recently I met with a woman who had two daughters. She wanted to convert her unfinished basement into a two‐bedroom suite. We were walking through her basement discussing the renovation when she asked if I heard about an earthquake that happened recently on Vancouver Island. She explained that her daughters felt the earthquake and started worrying about their house collapsing. She said quietly, “to be honest I’m a little worried about this house. Is there anything we can do to determine if it would be ok during an earthquake?” It was interesting that she had brought this up because I also have a daughter in her early teens who is also worried about our house collapsing in an earthquake. So here’s some things to think about if you’re ever wondering if your house would be vulnerable during a seismic event.

Determine When the House Was Built

This will give you an idea of the codes that were applicable during that time period, but keep in mind that renovations could have been done without adhering to any building codes. Her house was built in the 60’s and didn’t look to have any major structural changes. Seismic design has been apart of our building code since the 50’s, but there have been multiple revisions since that has enhanced a homes structural integrity to resist lateral loading caused by wind and earthquakes. Most houses around here are wood framed which typically perform well during a seismic event, so it is unlikely that a home would collapse during an earthquake as long as it was fastened together properly; however, in her case most of the walls were already exposed so we could see some issues immediately that could be remedied fairly easily without a lot of cost.

Anchor Every Part of the House

She had a pony wall on top of her foundation, but the wall wasn’t anchored properly to the foundation. This can be easily corrected by anchoring the bottom sill of the pony wall to the foundation using sill bolts. The required spacing is specified in the building code and can vary depending on the wall lengths and corners you need a minimum of two bolts per wall panel. Next, we noticed the pony wall didn’t have any sheathing. Without sheathing on a wall perpendicular to the lateral loading could cause the wall to collapse. This can be fixed by nailing plywood to the pony wall. The plywood thickness and nailing pattern are specified in the building code, keep in mind the orientation of the plywood matters and is specified in the BC Building Code. These two minor changes will increase her homes ability to resist seismic loading, is relatively cheap to do, and wouldn’t increase the renovation timeline. Incorporating minor seismic upgrades to your home during renovations can help keep your family safe without increasing your budget substantially.