The visible reveal between trim and frame needs an agreed consistent position. Existing irregularities can affect the result. Replacing decorative material does not authorise reshaping the structural opening or hiding a frame condition that needs separate repair.
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.
The base of an architrave often meets skirting of a particular thickness and shape. Include that junction in the enquiry. Replacing one trim element may expose a mismatch, but changing the entire room’s skirting is a separate decision and scope.
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.