of ir ranges from zero to one hundred with higher ir indicating a more unstable roof the interbedded shale with sandstone rating is defined as the value of ishwssr ranges from zero to one hundred with higher ishwsr indicating a more unstable roof sandstone with shale streaks sswshsr strata stores the most energy as compared to the previous types it easily delaminates at the shale streak bedding planes localized horizontal stress usually exists in this type of strata the release of this energy can cause strata delamination and roof cutter sandstone with shale steaks that is thick and close to the roofline creates an unstable roof therefore this rating also includes two parts thickness and interval the thickness rating tr is defined as where t is the thickness of shale with sandstone streaks the value of tr ranges from zero to one hundred with the higher tr indicating a more unstable roof the interval rating ir is defined as where i is the interval to the roof line the value of ir ranges from zero to one hundred with higher ir indicating a more unstable roof the second embodiment of the invention was used to calculate rir for another coal seam having an overburden depth generally ranging from 400 500 feet at the time of the underground.