What Size Nozzle Should You Use for Fire Door Mastic?

There is no single nozzle size that is correct for every fire-door mastic job. That is important because nozzle size is sometimes treated as a simple product question when it is actually an application-control question. Start with the product instructions Current manufacturer guidance is clear that the nozzle is cut to the desired bead size as part of the application process. Sika's Sikasil-670 Fire instructions explicitly tell the installer to fit the nozzle and cut it to the desired bead size before applying the product. That does not mean there is one universal cut size for every fire-door frame junction. The joint dimensions, material, substrate, backing arrangement and approved system all matter. Match the outlet to the line you are trying to place A nozzle that is too large gives you more material than you can easily control. You end…