For this mixed-window replacement project in Croxteth, opening checks, frame fitting and finishing are treated as one sequence. Perimeter Sealing leads the review, so we form a continuous weather-resistant seal around the external frame perimeter. We use trickle vents and installation access around frame dimensions, opening types, hardware, glazing and installation sequence, ensuring we integrate background ventilators with the frame head, room use and internal finish where specified and plan handling and working access before existing frames are removed, with perimeter sealing kept as the lead check for this mixed-window replacement scope. The last technical check is opening survey; we check the existing opening, frame position and surrounding finishes before final dimensions are confirmed, with perimeter sealing kept as the lead check for this mixed-window replacement scope. This supports different window types installed through one coordinated replacement package.