The interface property known as work of adhesion incorporates both adhesion and effective bond width, which are two important design parameters in thin spray-on liner (TSL) support design. The value of this parameter is yet to be recognized by the mining industry and liner manufacturers. The importance of this parameter is introduced in this study. A new methodology using pull-out load-displacement data was developed to calculate the work of adhesion between a TSL and a substrate. Tests were performed using Tekflex as a liner material, which was applied to concrete, granite or sandstone substrate. It was found that a Tekflex liner, when sprayed onto substrates, will likely have work of adhesion values around 777-973 N/m depending on the type of substrate. In addition, for the first time in TSL literature, an effective bond width calculation is introduced in this study. It was found that Tekflex has average effective bond width of 0.7 mm on different substrates. Liner manufacturers should measure and document work of adhesion for their products on a standard substrate.