Repair your Salisbury roof when damage is localised and the rest is sound; replace when nail sickness exceeds 30–40%, felt has failed widely, or repair costs approach replacement cost within 10 years. We give both options costed at a free survey with no pressure. Call 0172 223 9611.
The most common question we are asked during roof surveys in Salisbury is: should I repair this or replace the whole roof? It is also the most important decision, because getting it wrong in either direction costs money. This guide gives you an honest framework for making the right call.
When Repair Is the Right Answer
Repair makes sense when the problem is localised and the rest of the roof is in sound condition. The following situations almost always call for repair rather than replacement:
- Storm-displaced tiles — a discrete area of tile displacement from a wind event, with the surrounding roof in good condition
- Failed lead flashing — a specific flashing or valley section that has failed, with tiles and felt in sound condition around it
- Localised nail sickness — under 15% of tiles on a slope affected, with surrounding tiles still secure
- Ridge repointing — mortar recession without ridge tile displacement, on a roof whose tiles still have design life remaining
- Flat roof point repair — a discrete seam failure on an EPDM or GRP roof that is otherwise in good condition
Industry guidance holds that when repair costs exceed roughly 40% of replacement cost on a roof over 30 years old, full replacement usually offers better value over a ten-year horizon.
— NFRC lifecycle costing guidance
When Replacement Is the Right Answer
Replacement becomes the correct answer when the cumulative cost of ongoing repairs approaches or exceeds the cost of a new roof within a 10-year horizon, or when the underlying system has failed across a wide area:
- Widespread nail sickness — over 30–40% of tiles on a slope affected, where renailing would require lifting most tiles anyway
- Failed felt underlay — the underlay has been taking water across a large area and has deteriorated; felt replacement requires stripping the tiles regardless
- Roof over 50–60 years old with multiple concurrent issues — ridge failure, nail sickness and flashing failure together suggest the system is at end of life
- Storm damage covering large sections — where significant areas of tiles, felt and battens are affected
- Flat roof that has been repeatedly patched — a flat roof with multiple patch repairs across the field has systemic failure; replacement is more economical
The 10-Year Cost Test
A useful practical test: if the repair cost exceeds 40% of the replacement cost, and the roof is over 30 years old, get a replacement quote alongside the repair quote and compare the 10-year expected costs:
| Scenario | Repair now | Expected repair in 5 yrs | 10-yr repair total | Replacement now |
|---|---|---|---|---|
| 30% nail sickness, 3-bed semi | £1,500 | £1,800 | £3,300+ | £6,500 (25+ yr life) |
| Spot repair, isolated valley | £500 | Unlikely to recur | £500 | N/A — repair is right |
| 50% nail sickness + failed felt | £3,000 | £2,000+ | £5,000+ | £7,000 (25+ yr life) |
What a Good Roofer Should Tell You
Any reputable roofer surveying your Salisbury roof should:
- Assess the extent of any issues before recommending either course
- Give you both repair and replacement costs in writing if the decision is borderline
- Explain clearly what the repair will and will not fix
- Not pressure you toward the higher-value option
Be cautious of: Any roofer who recommends replacement after a cursory look at one or two slipped tiles without accessing the roof. And equally, any roofer who recommends repair-only on a roof with widespread nail sickness without giving you a replacement option. Neither position is honest.
We always give you repair and replacement costs where the decision is not obvious. Our surveys are free with no obligation to proceed. Call to arrange.
📞 0172 223 9611 — Free SurveyLast reviewed: 21 July 2026 by Salisbury Roofing Experts