Four signs that keeping it costs more than rebuilding it.
Not every old website needs a rebuild. A simple site that loads fast and brings inquiries steadily should stay as it is. The problem starts when the cost of keeping it becomes larger than the cost of replacing it.
First sign: the mobile experience is hard to use. If people have to zoom to read, or the contact button is covered, conversion is far below desktop. This alone is usually reason enough to rebuild.
Second sign: the content is no longer true. You added a service, changed prices, or stopped offering something, yet the site still advertises the old lineup. Visitors arriving from an ad notice the mismatch and lose trust.
Third sign: pages are slow and nobody knows why. If every content change waits on a vendor, or old plugins stop being updated, maintenance cost climbs month after month.
Fourth sign: you cannot measure what works. No tracking for forms, calls, or messages means every budget decision is a guess. Adding measurement is usually cheaper than a full rebuild, so start there.
Before deciding, list what is already working. Service pages that rank, content customers read, and keywords that bring inquiries are assets to keep. A rebuild does not have to mean deleting everything.
If the current site has search history, keep the old URLs and redirect where needed. Changing the whole URL structure without a redirect plan throws away rankings built over months.
Split the rebuild budget by work: content, design, development, and measurement. Many projects fail because every last bit of money went into design, leaving nothing for writing or tracking.
Set a concrete goal for the new site, such as more quote requests per month. With a number to compare before and after, you will know whether the rebuild paid off instead of just noticing that it looks nicer.
Above all, do not rebuild only because the site looks dated. Rebuild when it blocks people from understanding you, trusting you, and contacting you. The goal is more inquiries, not a new design to show off.