Yes, you can install drywall over plaster, but there are important factors to consider. While it can create a smooth, flat surface, it is often not the best approach. Installing drywall over plaster will increase the wall's thickness, which can cause issues with existing window and door frames that may no longer fit. You might also need to adjust power outlets to keep them accessible. A better, though more expensive, option is to remove the old plaster and lath entirely before installing new drywall. Drywalling directly over plaster seals in the old material, and if any problems arise later, you will need to remove both layers down to the structural beams for repairs. Given the potential complications, this job is best handled by professionals.

It's generally recommended to hang drywall on the ceiling first before moving on to the walls. This sequence allows the ceiling sheets to provide support for the vertical wall sheets. By attaching the ceiling drywall initially, you establish a solid framework to align and attach the wall panels accurately. This method ensures a seamless and sturdy connection between the ceiling and walls, resulting in a more professional finish.

Depending on the place where the cutting error occurred, you may be able to fix it. Learning how to patch a hole in drywall is challenging, but if you can tape and mud drywall, you can do it. Having said that, patching is time consuming. Early in the installation process, you may find that it’s easier and far less time consuming to just start over with a new sheet of drywall, cutting a new hole in the right spot. You may be able to use part of the incorrectly cut piece elsewhere, so it’s not completely wasted.

The person’s skill will affect how many drywall sheets they can hang in one day. Some people can hang 10 or more sheets in a day, while others may only hang six or seven sheets. It also depends on the framing complexity since custom cutting and fitting the drywall can prolong the process.