The change in the ablative writing sensitivity of Te films due to SiO2 and polymethyl methacrylate overcoats of various thicknesses were measured. These experimental data were compared to results of thermal calculations. We found that thermal losses of the absorbed laser energy to the overcoat layer is usually not negligible even for very thin (≲500 Å thick) overcoat layers. In addition to thermal effects which degrade the writing sensitivity of Te films, we found that rigid overcoats combined with rigid substrates can constrain the ablative writing process of Te and hence cause further degradation in the writing sensitivity and in the read-during-write signal.