I have an 1845 home with additions made in each century. There are 2 rooms which have painted canvas covered floors (sleeping porches?) The canvas was nailed to the floor, and I am guessing was also glued, since the edges have no nails. I have no idea what the sub-surface is, but the floor levels are lower than the adjacent rooms. Today the paint is severely cracked. I would like to preserve the canvas and repaint it, but it clearly needs to be sanded first. Any suggestions as to the best approach to prep and preserve this surface? I have uploaded photos of the 2 floors.