What kind of rent abatement can we ask of our landlord for some really severe health/safety violations?

My landlord has been renovating the apartment above ours for a month. Aside from the noise and vibrations (strong enough to knock clocks etc from the walls and break whatever's beneath it), we've had leaks in every room of the apt, which they patch with plaster that leaks through in a week or so, a plank of wood come through our ceiling, creating a hole 2 ft wide in our ceiling and tossing splinters of wood around my roommate sleeping feet away, and a crack in the ceiling in my room which leaked enough water to ruin my mattress. We now also have mold from the various leaks. The construction is expected to continue for another 2-3 months. What do not want to move from our home. They're dying for us not to take it to the city. What kind of rent abatement are we entitled to?