Hi.  Thank you for the efforts you have gone to, to help.  It appears that I have been using the only known solution know 'the sledge hammer' to get rid of them.  I have not noticed any missing ceiling, however, up until now I had not thought to look.  I did have one that was particularly difficult to get rid of under a bridge which is over a pond.  It was submerged below the water.  I was able to get it to emerge by placing foundations then deleting one foundation square at a time and when the 'sheet of paper'  reappeared above the water line I then was able to remove it (deleting the blocks of foundation together did not work as the sheet of paper returned under water). Thanks Again BillFlowerpot