Abstract Thermal conductivity is a key property that controls heat migration in a variety of applications including municipal solid waste and/or mining/industrial containment facilities. In particular, heat may be encountered in cases where geosynthetic lining systems are exposed to elevated temperatures due to either waste biodegradation, solar radiation, or mining processes. This paper presents the results of an experimental investigation on thermal conductivity of nonwoven geotextiles, geosynthetic clay liners and an HDPE geomembrane. A steady state method was used to measure the thermal conductivity of a selected number of these materials. The thermal conductivity of the HDPE geomembrane was found to be consistent with the thermal conductivity of HDPE polymer. On the other hand, the thermal conductivity of the nonwoven geotextiles depended on water content and whether they are hydrophobic or hydrophilic. The form of bentonite, its mass per area and water content affected the thermal conductivity of GCLs. The results presented in this paper provide a lower bound of thermal conductivities of geosynthetics routinely used in waste containment facilities.