An investigation of hydrogen-bond patterns in a family of ionic crystals has established the use of hydrogen bonding as a potential design strategy for crystal engineering of ionic materials. In 11 out of 12 crystal structures of anhydrous hydrogentartrate salts (data extracted from the Cambridge Structural Database), the anions were found to generate infinite two-dimensional sheets created by relatively short O–H⋯O hydrogen bonds. The regular occurrence of the infinite layer, even in the presence of widely differing cations, demonstrates the selectivity, strength and directionality of hydrogen bonds between ions in the solid state. The two-dimensional sheet was subsequently employed as a building block (‘scaffolding’) in the synthesis of a material with a threedimensional hydrogen-bond network, 1H-imidazolium hydrogen L-tartrate (the X-ray single-crystal structure is reported), where the cation provides the anticipated cross-link between adjacent anionic layers. Each anionic network was also described using a notation based upon graph theory which simplifies the process of recognizing and communicating complex structural information.