I live in a senior co-op and this question was posed to me: We have noticed several exposed roots on the west side of our building that originate from a large cottonwood tree (which is part of our property.). We are concerned whether these roots could cause any structural damage eventually. I have researched some possibilities but need more advice. Could we cut & remove some of the roots without killing the tree? I've read that a small percentage removal could be OK, up to 25%. I believe we have a thick slab under the blocks, as this is in the garage area. Chris from maintenance is also concerned the roots could interfere with lawn mowers.