Where are the requirements for door undercuts for fire-rated openings?
Consult with 2019 NFPA 80 - Section 4.8.4. You can view NFPA 80 for free at Free access NFPA codes and standards
hopefully this will answer your question:
18.104.22.168 the following job site preparations shall be permitted:
1) holes of surface-applied hardware, function holes for mortise locks, and holes for labeled viewers,2) a maximum 3⁄4 in. (19 mm) wood and composite door undercutting,3) installation of protection plates.
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