Knocking out a ceiling is simple and safe, if you take your time and use appropriate safety precautions, such as using a high-quality dust mask. Make arrangements for removing the old plaster and wood lath before you begin and be sure to call in a professional electrician to check out any wiring that you might expose.
Make plans for the removal of the old plaster and lath from the premises. This is a very important item that needs to be done before you actually start pulling down the plaster. The best way to go is to pay a rubbish removal company to set up a skip near the building that you are working in. Then you can gradually fill up the container until it is full. Then call the company and have them remove the receptacle. If you are just taking out a small amount of plaster, then you might want to place the material in the bed of a truck and haul the waste out on the same day.
Decide by what means you will get the old plaster from its original location to the skip or truck. If you will be tossing the debris out a window, then you may want to build a chute. This is done to protect the side of the building from incidental damage. A chute can be as simple as a sheet of plywood or you can acquire or rent a plastic tubular piece of apparatus that is specially designed for use by homeowners.
Disconnect the electricity for the room. Do this before you begin. This is merely a precautionary procedure that is as simple as turning off the circuit breaker for the area, where you will be working. If artificial lighting is needed then just run an extension cord from another room and attach some working lights.
Make sure everybody involved in the project has a high quality dust mask and appropriate protective gear, such as safety glasses, work boots and heavy gloves. Long sleeved shirts and trousers are also a must for this project.
Take a 90 cm (3 foot) crowbar, the kind that has one hooked end and one straight end and sink the curved end right into the surface of the ceiling. Drive it hard, so that the tip passes through the plaster and lath; then pull down hard so that a small amount of plaster and wood lath falls on the floor. The fun has just begun, for now you can go ahead and pull down all loose plaster with the crowbar. Be mindful of the electrical wires that might run through the ceiling. Their presence is usually simple to find. All you need to do is look for overhead lighting fixtures. Be sure to keep an eye out for old fixtures that are no longer in use.
Take a close look at the edge of the room and make sure that the lath and plaster network does not continue into the next room. If this is the case, then you need to cut the plaster and lath with a large reciprocating saw, so that nothing in the next room comes loose. Make sure you do not cut any wires.
Clean up all the nails that are sticking out of the floor joists and remaining debris with a claw hammer or a smaller pry-bar. You may need a stepladder, for this but make sure the old ceiling rafters are clean of debris.
Turn on the electricity and remove all debris to your pre-arranged disposal container. Once this is done, you will be ready for whatever comes next.
Take a close look to see it the ceiling is continuous with any other rooms. The older the building the more likely that you might come across this situation. One clue is that if there is a non-support wall that divides a large space into smaller units, then you might be looking at a continuous ceiling. If you expect such take an old utility knife and cut as deep as you can into the old plaster at the corner of the ceiling. Try pulling away as much plaster as you can without disturbing the wood lath. Then cut the lath with a sawsall. Even if you do a good job with this, you are still likely to knock loose some plaster in the next room.
Old dust is a health hazard if it is inhaled. Also watch out for old electrical wires running between the ceiling joists.