The bilinear brittle failure criterion that utilizes the unconfined compressive strength (UCS) and a spalling limit of 3.4, together with a tensile strength cut-off can be used to model the height of failure above coal mine roadways. Transverse isotropy can be incorporated into a continuum analysis by using a Young’s Modulus/Independent shear modulus ratio of 15. To predict the height of failure, the two key variables are the roof strength index (UCS/pre-mining vertical stress) and the horizontal to vertical stress ratio. By factoring in the stress concentrations that occur about a longwall excavation the criterion can be used to predict heights of failure on initial roadway development and in the maingate. A support design based on dead-weight suspension of the failed mass can be utilised.