Should you repair or replace your roof?
The signs that a repair will do, the signs it won’t, and how the costs compare over ten years.
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Last updated 27 October 2026
Most roofs don’t need replacing just because they leak. But on older Merthyr terraces, many roofs are past the point where patching makes sense. Here is how to tell which you have.
Signs a repair will do
- The problem is in one place: a few slipped slates, one cracked ridge tile, or a leak at the chimney
- The roof line looks straight from the street, without dips or sagging
- From the loft, the felt and timbers look dry and sound
- It’s the first repair in years
Signs it may be time to replace
- Slates slipping all over the roof, often from “nail sickness”, where the old nails have rusted through
- Felt in the loft that is torn, brittle or missing, or no felt at all on very old roofs
- Daylight through the roof, or damp patches on rafters in several places
- The ridge or roof slopes visibly sagging
- You’ve paid for repairs more than once or twice in the last few years
Comparing the costs
A single repair costs far less than a new roof, but scaffolding can add a lot to a small job. If you are paying for repairs most winters, a new roof can work out cheaper within a few years, and it adds value when you sell. See our roof repair cost guide and new roof cost guide for details.
Questions to ask the roofer
- What do you think caused the problem?
- How long should this repair last?
- What condition are the felt and battens in? Can you show me photos?
- If I repair now, what is likely to go next?
A good roofer will explain their thinking and show you photos. If one roofer says you need a new roof and you’re not sure, it’s reasonable to get a second opinion.
More guides
Questions people ask
How do I know if my roof needs replacing?
Slipping slates in several places, perished felt you can see from the loft, sagging along the ridge, daylight through the roof, and paying for repairs every winter are the main signs. One problem in one place usually just needs a repair.
How long does a roof last?
Concrete tiles last 40–60 years and natural slate 80–100 years or more, but the nails, felt and battens underneath often fail first. Many Merthyr terraces have slate that is still good on nails and felt that are not.
Can a slate roof be stripped and the slates reused?
Sometimes. If the slates are sound and it is the nails or felt that have failed, a roofer can strip, sort and refix the good slates over new membrane and battens, topping up with reclaimed slate. It is cheaper than new Welsh slate and keeps the look.
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