Unreinforced Masonry Buildings

Unreinforced masonry buildings (URMs), are old brick buildings typically built prior to 1945. Because these buildings were not built using modern building codes, they are much more likely to experience damage or collapse during an earthquake. Most URMs have brick walls and wood-frame floors and roofs. A tell-tale sign of URM construction is what's called header courses- lines of bricks turned on end. Seattle has an estimated 1164 URMs throughout the city, and many can be found in historic neighborhoods such as Pioneer Square, the International District, Capitol Hill, Columbia City and Ballard.

URM header sourse diagram

During an Earthquake

URMs are vulnerable to damage and collapse during earthquakes because the parapets and walls are not secured to the roofs and floors. Parapets can break away, falling into the street and putting pedestrians in danger. Walls can break away and lead to full or partial collapse. Seismically retrofitting a URM reduces this danger.

Parapet breaks off (URM)

Building Collapses (URM)

graphic of building wall collapsing as floors seperate from wall

Building stays intact (Retrofit)

image showing building shaking and walls staying connected to floors with bolts

Seismically Retroffiting URMs

Seismic retrofit diagram showing various elements of a retrofit

Graphics: Stephanie Redding | The Seattle Times. "Seattle's old brick buildings could see huge damage in big quake," Seattle Times, August 10, 2015.

Right now, there are no retroactive regulations in the City of Seattle requiring owners of URMs to upgrade their buildings through seismic retrofitting. However, if you do decide on a major renovation, re-occupy a vacant URM, or change the use occupancy of a URM you currently own, you may be required to comply with seismic regulations in the current Seattle Building Code. The City is considering a mandatory URM retrofit policy. You can learn more about this through the Department of Construction and Inspections.