The modelling of the mean reaction rate in a premixed turbulent flame is approached by means of a library of laminar flame solutions. A formulation of such a library is presented and the detailed data requirements are investigated. Laminar flame calculations are performed in an asymmetrical counterflow configuration with a cold, reactive methane-air mixture flowing against the corresponding hot equilibrium combustion products. The flamelet properties required for the library are shown to be independent of the definition of a reaction progress variable c. Stoichiometric flames at pressures of 1 bar, 1.5 bar and 2 bar are considered, with corresponding initial temperatures of 328, 386 and 433 K. The results are examined in the light of the demands of the library, and suitable definitions of key quantities are proposed. A specimen laminar flamelet library is then assembled.