Where replacements go sideways, and how to not
Dimension optimism is failure mode one: nominal sizes hide real variation, and an alcove tub a half inch proud of its opening is a return, not a shim job. Measure the existing opening at multiple points, compare against the replacement's specification sheet rather than its marketing page, and confirm which end the drain occupies, left and right versions exist for a reason.
The route is failure mode two: tubs are rigid, awkward, and unforgiving of tight stairwells and low soffits. Walk the route with boxed dimensions, including the turn into the bathroom itself, before purchase; the alternative discovery method involves two movers, a stuck landing, and a restocking fee. Weight is the quieter cousin: cast and stone pieces may want structural review, and the answer changes by floor level.
Connections finish the job right or wrong: drain and overflow must align or be rebuilt, freestanding fillers need supply routed to open floor, a decision with its own under-floor consequences, and larger tubs test the water heater's real capacity. Installation closes with leveling, support per the manufacturer's method, and a fill-and-drain test before the surround closes, because the cheapest leak is the one found while the access is still open.
