cellio | daf bit: Bava Batra 18

The talmud now turns to things that, while done on your property, can encroach on your neighbors and so are further restricted. The mishna lists several things that must be set back at least three handbreadths from your neighbor's wall, including ditches, olive refuse, dung, salt, lime, and flint-stones, unless he plasters them. (In the case of the ditch it means plastering the sides so it can't erode and undermine the wall; it's not clear to me how plastering would apply to the others.) The g'mara then asks: it says his wall; does this mean that if there is no wall he can place these right up against the property line? No, they still have to be set back, but the mishna mentions a wall because these are all things that can damage a wall if in contact. The mishna also lists mill-stones; here the reason in the g'mara is that the vibration from milling can cause damage (and there is no plastering contingency). Ovens, too, because of the heat. The g'mara then adds that one may not open a bakery or a dyer's shop under another's storehouse, nor place a cowshed there, though if the cowshed was there first he may keep it. (17a mishna, 18a g'mara)