A roof collapses if there s no support rock wall within 6 squares of the tile. Then get your miner to take out each support from the adjacent outside tile so that when the rock collapses the miner isn t underneath. You can help rimworld wiki by expanding it. 
				
			
										if the power goes out and you have solar panels
											in floor parts
											ikea curtain panel track
											how to install rain gutter mioter strips
											ikea double glass door cabinet
											how to shingle a flat porch roof
											humor funny roofing memes
											how to raise the roof of a garage