Start with the honest default
Most leaking roofs don't need replacing. One failed detail — a slipped slate, tired flashing, a blocked parapet gutter — accounts for most of the calls we get, and a targeted repair sorts it for a few hundred pounds. A roofer who jumps straight to "you need a new roof" from one damp patch is selling, not surveying. But there genuinely is a point where patching becomes a waste of your money — here's how to tell.
The four tests
- 1. Fixings, not just slates. Victorian and Edwardian roofs were nailed a century ago, and when "nail sickness" sets in the slates slip one after another — each in a different place. If slates are slipping across the whole roof rather than around one detail, the fixings are done, and every repair is a loan against the next one.
- 2. The habit test. One repair in five years is a repair. Three repairs in two years, in different places, is a roof telling you something. Get the invoices out and count — the pattern is the diagnosis.
- 3. One slope or everywhere? Damage concentrated on one slope or around one chimney usually means a local fix, even a big one. Problems spread across every slope point the other way.
- 4. What's underneath. Go up to the loft on a bright day. Daylight through the covering, crumbling or absent felt, watermarked timbers or damp insulation mean the roof's supporting layers are failing — and those can't be patched from above.
The money math
Repairs are typically a few hundred pounds. A full re-roof on a London terrace lands somewhere in the £6,000–£15,000+ range depending on size, materials and scaffold. So the crossing point is real but it's further out than the salesmen suggest: you'd need years of repeat repairs to spend re-roof money. Where replacement wins is when the roof is failing generally — because then you're paying for scaffold and access again and again while the ceilings and decoration take damage that costs extra to put right each time.
If it is time: what a proper re-roof includes
A re-roof means stripping the old covering, checking and repairing the timbers, new breathable membrane and battens, renewed leadwork at chimneys and parapets, and the slate or tile laid to last decades. Be wary of quotes that look too cheap — the corners cut are the ones you can't see from the street, like reusing tired leadwork or skipping the membrane. On conservation streets, matching slate isn't optional, and we'll tell you what the council will expect.
What a good survey gives you
Photos of the actual problems, a plain-English explanation, and — where both options are viable — a price for each, in writing. That's what our free survey does, and there's no call-out charge and no obligation. If you want a starting point today, our roof inspection page explains the photo-report service.