Our apt. building is undergoing redecorating, which will require painting of all apt. doorways. I had always been taught that a Mezuzah remains on the door until the occupant leaves. The contractors have been instructed to put a protective covering on any Mezuzahs and paint around them. Is this correct, or should people take their Mezuzahs down and then put them back when the renovations are completed?

The Mezuzot may be taken down, and should be if there is the slightest chance they will be damaged (not uncommon even with good intentions of the contracter). Its also a good time for an examination.