Abstract: The present disclosure is directed to door assemblies in SCIF and RF applications and methods of installing the same. The door assembly includes a frame assembly with two jambs and a frame header. Each jamb defines at least a central jacking block notch and outer jacking block notch. The door assembly further includes a plurality of jacking blocks, with a jamb side and a door side opposite the jamb side. The jamb side of each jacking block is received within each of the notches. The door assembly further includes a temporary spreader bar coupled to the door side of each jacking block, a threshold, and a seal retainer cover disposed above the threshold along a vertical axis. The threshold is partially disposed below the seal retainer cover such that the seal retainer cover and the plurality of jacking blocks restrict lateral movement of the threshold.