The decorative material needs sound ordinary support and appropriate fixings. Hidden services and uncertain substrate must be considered before attachment. This task excludes structural reinforcement and should not be used to stabilise an unsound frame through decorative trim.
Agree filling, joint preparation and the painting boundary. A primed replacement can still need final decoration after fitting. Window glazing, specialist seals and rated-door certification are outside the task even where the new architrave sits beside those systems.
Top corners and returns need appropriate ordinary cutting and fitting. Show any unusual junctions before ordering material. A compatible profile and adequate lengths matter; filling large mismatches is not equivalent to a properly planned replacement surround.
Replace the accepted ordinary decorative surround with suitable joints and fixings, leaving the agreed preparation for finishing. Scope limits: Ordinary decorative surrounds only. No structural jamb or opening modifications, specialist glazing, fire-door certification or hazardous-material disturbance.