We turn down full-roof replacement quotes regularly because the roof in front of us doesn't need one. Here's how to tell the difference between a roof that needs work and a roof that needs replacing — and the warning signs that someone's trying to sell you something you don't need.
Signs you genuinely need a new roof
Widespread nail sickness across multiple bays. If twenty slates are slipping across the front elevation and you can see twenty more about to go, you've reached the point where re-laying isn't cost-effective — a strip-and-re-cover with copper fixings is the right answer.
Structural sag in the rafters or purlins. Once the underlying timber has failed across more than one bay, you're rebuilding the roof anyway — covering is the cheap bit at that point. (Single-rafter sag is usually fixable with sistering; see our sagging roof guide.)
End-of-life flat roof on a habitable extension. Felt over 20 years old on a kitchen or bedroom extension is a now-or-soon decision, especially if you've already patched it twice.
Multiple, repeat leak points after recent repairs. If a roofer has fixed three separate leaks in 18 months and a fourth is appearing, the covering is at end-of-life and patching is throwing money away.
Signs you DON'T need a new roof
A single leak. One leak is almost always a one-visit repair — a slipped tile, a lead apron, a short valley re-line. Anyone quoting a full re-roof for a single leak is selling, not diagnosing.
Moss growth on the north slope. Moss looks dramatic and is almost always cosmetic. (See our honest moss guide.) A jet wash will do more damage than the moss ever will.
One sagging area on an old roof. Sag that's been stable for decades, isn't progressing, and has dry loft timbers is a tired-but-safe roof. Monitor with photos; don't panic.
Visible nail sickness on a few slates. Two or three slipped slates on a Victorian terrace is a £200 re-fix, not a £15,000 re-roof. Welsh slate is designed to be re-laid; that's part of why it lasts 100 years.
How to spot a sales pitch dressed as a survey
- The "surveyor" only goes on the ladder, not in the loft. Real diagnosis happens from inside as much as outside.
- You're offered a discount "if you sign today." Genuine roof quotes don't expire.
- The recommended fix is always a full re-roof regardless of the symptom.
- Photos are vague, taken from the ground, or none are provided at all.
- There's no written method statement, just a price.
What an honest survey looks like
A proper inspection includes: a loft inspection (timber condition, ventilation, condensation history), a covering inspection (where possible from a tower or scaffold, not leaning off a ladder), photographs of every defect found, and a written report that distinguishes "must do now," "will need within 5 years," and "monitor only." If a roof needs re-covering, the report explains why and shows the evidence. If it doesn't, the report says so.
Getting a second opinion on any quote over £5,000 isn't insulting to the first roofer — it's basic homeowner due diligence and a reputable roofer will encourage it.