When Seattle Shakes

Downtown Seattle Skyline with Unreinforced Masonry Buildings

Bracing Seattle for the Next Earthquake

For the Emerald City, it’s not a question of if a major earthquake will strike but when. That’s why Holmes sponsored When Seattle Shakes—an online exhibit on mitigating seismic risk for existing buildings in Seattle through resilient design.

The Seattle Fault and Cascadia Subduction Zones are capable of causing extreme damage to existing buildings during an earthquake. Unreinforced masonry buildings prevalent downtown and in the Seattle region are notably at risk: left unaddressed, they compromise public safety alongside architectural heritage. Whatever the age or type, we can assist you in evaluating and when necessary bolstering your building. Where required, we’ll supplement with only the strengthening needed to meet seismic demand. Whether you’re preserving a historic structure or breathing new life into an existing one, Holmes can help.

Want to chat about your building in the Seattle area?
Reach out to Principal Greg Briggs.

Contact Greg

Unreinforced Masonry and Existing Buildings in Downtown Seattle for Structural Engineer Retrofit

Our Evidence-Based Approach

We utilize advanced structural analysis combined with comprehensive 3D models to understand a structure’s inherent strengths and vulnerabilities. With these models, we test, refine, and iterate upon retrofit solutions by simulating the response of the retrofitted structure to recorded earthquake ground motions.


We supplement our analyses with evidence-based design. We take actual materials and components from the existing structure, bring them to the Holmes lab, and test them to better understand their response to earthquake loads.

Material Testing on Holmes Shake Table at Holmes Test Lab New Zealand

Bill Tremayne, Principal and Technical Director with Holmes Structures, Assesses Structural Analysis

Our approach delivers better performing, more cost-effective, and less intrusive seismic retrofits. These solutions are more compatible with the existing structure and historic fabric.

Bill Tremayne, Technical Director
Holmes Group Testing Lab in Christchurch New Zealand with Shake Table
The Holmes Test Lab

Drawing from International Expertise

Founded in New Zealand with offices across the Pacific Ring of Fire, Holmes Group has substantial experience in assessing and repairing post-earthquake damage. In recent years, our engineers have sprung into action on emergency response teams for the Canterbury and Kaikoura earthquakes in New Zealand, as well as for earthquakes in Napa, Mexico City, Central Italy, and further afield.

We’ve taken stock of destruction amidst the rubble and apply the lessons learned to achieve our clients’ goals. We evaluate and strengthen vulnerable buildings—including unreinforced masonry, non-ductile concrete, and soft-story structures—while respecting each project’s context and constraints.

Damage to Unreinforced Masonry Building after Canterbury Earthquake in Christchurch New Zealand
Christchurch Arts Centre: post-Canterbury-earthquake damage.
Retrofit of Christchurch Arts Center in New Zealand after Canterbury Earthquake
Christchurch Arts Centre: retrofit implementation.

In Case of Fire

History has shown that major earthquakes can be followed by devastating fires. From a fire and life safety standpoint, Holmes devises economically viable, flexible solutions that cater to the needs of each existing building. It’s never a one-size fits all approach. Still, we follow some guiding principles to get the job done. First and foremost, we determine a means of egress system that gets occupants out of the building safely in the event of a fire. Our solutions protect the property and preserve any elements that are historical in nature. They also provide reasonably secure platforms for the Fire Department to operate from, reducing hazards as much as possible.

Seattle Existing Buildings When Seattle Shakes

Every building has its own history with the city that is worth preserving. It’s also greener to upgrade and save an existing building than it is to demolish and start from scratch.

More Perspectives

We bring deep knowledge of retrofitting unreinforced masonry buildings.

Leading URM Building Retrofits