The thixotropic properties of contemporary mortars allow the insertion of mortar in small vertical seams by using a mortar pump without the need for traditional formwork. In such a seam, a vertical mortar connection for the transfer of shear forces can be created by simply adding a profile to the mortar-to-concrete interfaces. In this way a constructible continious vertical shear connection can be constructed between storey-high precast concrete wall elements. In this investigation, narrow vertical mortar connections are developed for the transfer of shear forces in precast concrete shear walls with tying reinforcement in the slabs. The shear behaviour of five versions with differently shaped mortar-to-concrete interfaces is obtained from shear tests. All experimental results are presented and discussed, while the shear behaviour of the Staggered shear key connection is analysed in detail. Also, the shear behaviour of the five mortar connections are mutually compared and assessed on their performance for functioning as a vertical mortar connection. A diagonal bar model is proposed for simulating the shear behaviour of the Staggered shear key connection, which is called the “inclined compression strut model”. Also, an equation for predicting the shear capacity is proposed. The functioning of the model and equation are investigated by applying them in case studies with cantilever shear walls in versions with and without window openings.@en