This practical step‑by‑step guide covers site survey, old panel removal, steel‑structure pretreatment, PU sandwich panel selection, installation, acceptance and post‑operation maintenance for old factory reconstruction and cold‑storage renovation projects. It helps engineering teams avoid common retrofit risks. SAMZOON, Foshan local source manufacturer, provides customized PU sandwich panel, fast‑track production, free samples and full‑set construction technical guidance for South‑China retrofit projects.