Final answer:
To fireblock a drop ceiling, install fire-resistant materials such as mineral wool, fire-rated caulk, or expanding foam in gaps between the ceiling and above structures, and seal penetrations with fire-rated sealant, all in compliance with building codes.
Step-by-step explanation:
To properly fireblock the bottom of a true 'drop ceiling' that is framed in with lumber and drywall, you need to create a barrier that prevents the spread of fire and smoke through the open spaces above the ceiling. The process involves using fire-resistant materials such as mineral wool insulation, fire-rated caulk, or expanding foam. These materials should be installed in any gaps between the top of the wall and the bottom of the above floor assembly or roof sheathing. Furthermore, it's important to seal around penetrations like pipes and electrical boxes using fire-rated sealant.
In some cases, you may need to install additional framing members to support the fire-blocking materials. Firestops must be installed in compliance with local building codes and standards, which often refer to the National Fire Protection Association (NFPA) codes or the International Building Code (IBC). It’s always best to consult with a professional or refer to the specific codes applicable to your area for guidance on materials and installation methods.