The described features include a scalable waveguide architecture for a waveguide device. The waveguide device may be split into one or more waveguide blocks instead of manufacturing increasingly larger single-piece waveguide devices. Described techniques provide for a radio-frequency (RF) seal between such waveguide blocks that may facilitate greater manufacturing tolerances while maintaining an effective RF seal at the junction of the waveguide blocks. The described techniques include channels within one or more waveguide blocks opening to the dielectric gap between the waveguide blocks. The channels may, for each of multiple waveguides joined at the interface between waveguide blocks, be included in one or both waveguide blocks and may be in a single waveguide dimension relative to the multiple waveguides, or extend for more than one waveguide dimensions.