Strengthening Unreinforced CMU Walls NW Cornelius Pass Rd. Portland, OR


This project included mitigating hazards from an existing one story unreinforced concrete masonry building. Unreinforced masonry buildings have a limited capacity to resist seismic loads. Unreinforced masonry buildings in particular are highly susceptible to wall collapse as a result of out-of-plane loads on walls from seismic and wind forces.

The construction on this project included a new building addition attached to an existing commercial building structure. The existing unreinforced masonry wall was strengthened using wood framed studs. The wood framed studs provided a mechanism to resist the seismic forces (they effectively give the wall a backbone). The SR wall system was used to attach the masonry wall to the reinforcing studs. This was done by sheathing the wood studs with plywood, and filling the cavity between the masonry wall and the wood stud wall with SR Foam adhesive. SR Foam adhesive acts to connect the masonry wall to the stud wall. In addition to reinforcing the CMU walls for out-of-plane forces, the plywood sheathing also provides in-plane resistance, and was used as a shearwall.

The new strong-back wall not only provides resistance to seismic forces and prevents the original wall from collapse, it also acts as a bearing wall and acts as a secondary support to carry roof loads. This strengthened wall would be able to remain a bearing wall and support the roof structure in order to protect occupants in both the new addition and adjacent existing spaces during a seismic event.

Without the SR Foam adhesive, a method of attachment using discrete fasteners would be required. SR Foam adhesive eliminates the need for these fasteners reducing labor required for construction. SR Foam adhesive provides a highly aggressive permanent bond between the existing wall and the new wall that is fully tested. The SR Foam is a highly insulative material and provides a superior resistance to heat loss in the building.

For this project the new wood-stud strong-back wall was installed with a 2 1/2 inch cavity of SR Foam adhesive (approximately 114 cubic feet of SR Foam). 

Project completion: October 2013