An educated estimate of changes of mechanical properties of polymeric mortars under environmental actions requires further knowledge since data are insufficient and the understanding of alterations incomplete. An experimental program to generate information on those aspects for artificially aged coupons of polyester and epoxy mortars is described. At pre-established temporal stages, flexural tensile bending and compression strength of coupons was determined and compared. Environmental conditioning consisted of cycles of (i) temperature; (ii) humidity and (iii) salt fogging, emphasis being, herein, placed on the effects of the temperature and humidity cycles. Thin lamellae of the tested coupons were cut along the ageing process and observed under petrographic microscope. Changes on the aspect of air voids and textures are reported. A systematic SEM study of the mineralogical and textural aspects is also presented that qualitatively contributes to the interpretation of the results. Higher degradation was detected in the samples submitted to the temperature and salt fogging cycles selected in the study and seen to intensify past 3000 It of accelerated environmental action.