Repair or replace? How to tell when a roof is done

Start with the age

Concrete tiles last 50–60 years, clay 60–100, natural slate 80–150, three-layer felt 15–20. A 30-year-old concrete roof with a leak almost certainly needs a repair. A 70-year-old one with several problems is at the end.

Then the four questions

1. Is it one thing or many? A single slipped tile, one cracked flashing or a blocked valley is a repair. Leaks in three places at once usually means the whole covering is failing.
2. Are the fixings gone? On old slate roofs the slates are often fine but the nails have rusted through — 'nail sickness'. You can re-fix a few; once they're sliding off across the roof it's a re-slate.
3. What's the underlay like? Older roofs have bitumen felt that goes brittle and tears. If the felt has gone, water that gets past the tiles has nowhere to go but in.
4. Is the timber sound? Sagging between the rafters, rot at the eaves or a spongy deck on a flat roof means the structure needs work, and that's a strip-off job.

When a repair is the honest answer

If the roof is under 40 years old, the fault is localised and the underlay and timbers are sound, repair it. A good roofer will say so even though a re-roof is a bigger job for them.

When it isn't

If you're paying for a repair every winter, the money is going into a roof that will still need replacing. Add up the last three years' repair bills and compare with a re-roof quote.

Not sure which yours is? Book a survey and we'll tell you.