Canada’s building stock consisting of unreinforced masonry (URM) components is facing a consistent threat. Nearly 50% of URM structures were built before 1970 which makes them vulnerable to seismic events, settlements and floods that are furthermore intensified with climate change. Retrofitting old URM structures is a key solution to enhance life safety, avoid possible demolition and deconstruction that are contributing to Canada’s increasing solid wastes. Unlike traditional retrofitting techniques, using polymeric materials for retrofitting is becoming a versatile approach due to it being cost-effective, durable and a non-invasive option. This paper aims to use polypropylene geogrid material as a strengthening option for old URM buildings. The experimental campaign consists of six double wythes wallets that are constructed using solid clay bricks, type O mortar with addition of sand to replicate the structural properties of old URM buildings. Two specimens are considered control specimens and the remaining four underwent retrofitting with geogrid overlays as a seismic system intervention for in-plane loads. Each sample was loaded in compression diagonally, causing a diagonal tension failure following the ASTM E519 guidelines. Design parameters of the adopted strengthening system included different configurations. Results exhibited improved in-plane shear strength and displacement capacity.