Aging intercom systems create a familiar set of problems: dead units, missed deliveries, and no reliable way to verify who’s at the door. The natural assumption is that fixing this means tearing out walls and rewiring the entire building. That assumption is usually wrong.

Most legacy wired, buzzer, or telephone-entry systems can be upgraded to a modern video intercom by reusing a meaningful share of existing infrastructure — door hardware, conduit, mounting locations, and pathways — rather than opening walls to create new ones. In most cases new cable is pulled through the conduit that’s already there.

This guide walks through how to evaluate the options: how to decide between repair, retrofit, and full replacement, what each path typically costs per entry point, how to plan around resident disruption, and what to ask any installer before signing a quote.