The honest headline numbers, for UK conditions and decent workmanship: natural slate 80–100+ years; clay tiles 60+; concrete tiles 40–50; modern flat systems — EPDM and GRP — 25+; torch-on felt 15–20. But the covering is only part of the story, and usually not the part that ends it.
The parts that retire first
A roof is a team, and the covering is its longest-serving member. Underlay: traditional bitumen felt manages 40–60 years before it embrittles — many "worn out" roofs are sound tiles over dead felt (more on membranes). Fixings: the nails holding slates commonly rust through decades before the slate fails — "nail sickness", the classic reason century-old slates get re-laid on new fixings. Mortar: ridge and verge bedding is good for perhaps 25–40 years per application, which is why dry-fix systems exist. Flashings: lead does 50+; the sealant "repairs" people substitute for it do two or three.
What shortens a roof's life
Exposure, aspect and neglect of the small stuff. A hilltop gable taking every south-westerly ages faster than a sheltered semi. North slopes hold moss and moisture. And little failures left alone become big ones: one slipped tile exposing the felt, one blocked valley soaking a timber. The cheapest life-extension a roof can have is boringly simple — gutters cleared, slipped tiles refixed promptly, a proper look every few years.
Knowing where yours is on the curve
If your roof is original and your house was built in the 1960s–70s, its concrete tiles and felt are both in the retirement window — worth a proper inspection even if it "looks fine from the street". Victorian slate with slips every winter is asking about its nails, not its slates. And any roof you're about to buy deserves better than the mortgage survey's glance from the pavement. An inspection costs little and turns guesses into a plan — ask us.