Measure both sides and the top and identify whether one face or both are included. A doorway may have different trim on each side. The quote should describe the actual surround instead of assuming one opening means every adjacent decorative surface.
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.
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.
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.