The time-dependent deformation of an NHL3.5 natural hydraulic lime mortar has been investigated, through creep and drying shrinkage under load. An apparatus was constructed to measure the dimensional changes of eight individual samples simultaneously. A reversible relationship between changes in specimen dimension and relative humidity has been established. The influence of load on deformation rate was found to be most significant during the first two weeks of monitoring with little effect thereafter. The rate of deformation during the first 2 weeks of sample monitoring was proportional to the applied load. A logarithmic creep expression of the form ε=Aln(t)+B gave the best fit to the data where, ε is strain, t is time and A and B are constants. A linear relationship was found between the coefficient A and applied load.