The thermal performance of a concrete roof with a phase change material (PCM) layer on its interior surface under a Mexican warm weather (Merida) is presented. We analyzed a roof with three types of PCM: Paraffin wax - MG29 (R-PCM1), N-Eicosane (R-PCM2), and Salt Hydrates (R-PCM3). We also considered different thickness of the PCM layer. A conventional concrete roof (R-C) was considered as a reference to compare the results. The numerical simulations were conducted during the warmest and the coldest days of the year. A numerical in-house code was developed, and it was verified by solving reference solutions, obtaining good agreement. The results indicate that the case R-PCM1 with 2 cm of PCM layer had the lowest values of thermal load during the coldest (204.5 W h m(-2)) and the warmest day (610.7 W h m(-2)); such values are up to 57% lower than the thermal load corresponding to the R-C. The use of R-PCM1 with 2 cm of PCM-layer in Merida city will have a payback period of 12.18 years, Taking into account that buildings in Mexico have a 30-year ordinary service life, the use of these materials is cost-effective. Therefore, it is recommended the R-PCM1 to improve the thermal behavior of buildings located in Merida. (C) 2019 Elsevier Ltd. All rights reserved.