The dimensional stability of calcum silicate hydrate phases (C–S–H), (with varying C/S ratios) in saturated-lime water, distilled water and a methylene solution was investigated in this study. Two distinct regions of C/S ratio exhibited maxima in length change versus C/S ratio curves generated from results in all three test solutions. Differences in behaviour in all three solutions were minimal. It would appear that the C–S–H nanostructures that quickly form in methylene solution are comparatively stable in aqueous media. Possible mechanisms for the length change behaviour are discussed.