Our house is about 85 yrs old and all the plaster walls are cracking at the top and corners and some places just anywhere. We would like to put up sheetrock however our house was built very solid. They say the outside walls were built as such brick, cynder block, some kind of tiles and then plaster. With all this it makes the outside wall like rock. We cannot get anything to drill into the walls. We hung a drop ceiling and used a mason drill bit but it took several bits they kept breaking. Any suggestion on how we should get the sheetrock to stay up. And we can only find very minimal wall studs if any.