The use of mass timber has risen dramatically in recent years and is expected to continue to grow as the structural engineering community seeks sustainable alternatives to steel and concrete. As the use of mass timber grows, so too will the need to develop efficient and effective retrofitting solutions to increase load-carrying capacity, either because of a change in occupancy or a deterioration in building condition over time. One such solution is the use of externally bonded fiber reinforced polymer (FRP) sheets, however, limited research on FRP-to-timber composites means that current design codes (e.g., CSA S806, ACI 440) lack guidance on how to design FRP-timber retrofits. This research assesses the behaviour of flexure critical glued-laminated (glulam) timber beams reinforced in tension with externally bonded FRP sheets as well as in compression with near surface mounted (NSM) reinforcing bars. Results of the study indicated that FRP sheets can successfully change the failure mechanism of a glulam beam from brittle tension to more ductile compression while also increasing the load carrying capacity by up to 100% when compared to the unretrofitted beam. Distributed fiber optic sensors (DFOS) were used to assess the behaviour of the beams by enabling quantification of the relative contributions from the timber, FRP, and metallic reinforcement to the total load carrying capacity of the members which will aid in the development of design methods in the future.