Does an old roof automatically need replacing?

The covering is usually the longest-lived part of a traditional roof. Nails, mortar bedding, underlay and battens age faster, and they are what tends to determine when a roof needs renewing. That is why a slate roof can look old and still be sound, while its fixings are the real subject.

On more recent roofs the picture inverts: concrete tiles often outlast the battens and underlay beneath them, so the question is about the layers you cannot see.

Whether coverings are moving, and in how many unrelated places. Whether underlay is intact and flexible. Whether battens are sound where they can be seen. Whether details — ridge, verges, valleys, flashings — are serviceable or have been patched repeatedly.

Each of those is a specific finding. A recommendation built on them is credible; one built on the roof's date of construction is not.

Keeping drainage clear, dealing with vegetation, and renewing details as they fail extends serviceable life considerably. So does inspecting periodically so that slipping is caught before it becomes ingress.

None of that is an argument for keeping a roof that has genuinely failed. It is an argument for deciding on evidence.

Building records, previous invoices and even planning documents sometimes show when a roof was last stripped, when a covering was replaced, or when significant repairs were carried out. That history narrows the guesswork around age considerably, because a covering re-laid twenty years ago behaves differently from one that has never been touched since construction.

Where no such record exists, a contractor should say so plainly rather than presenting an estimate of age as if it were established fact. The distinction matters when it comes to weighing a replacement recommendation.