Repair your Stratford roof if damage is localised and the underlay and battens are sound; replace it if tiles are widely slipping from nail sickness, the felt has failed, or repairs are becoming frequent. A one-off repair costs £150–£900; a re-roof £5,500–£15,000. A survey of loft and roof condition settles the decision.
The repair-versus-replace decision is the most consequential roofing choice most homeowners face. Make the wrong call and you are either spending £400 per year patching a roof that should have been replaced, or spending £7,500 on a full re-roof that a £600 repair would have deferred for another decade. This guide gives you the framework we use at every survey to arrive at an honest recommendation.
The Three-Factor Assessment
Every survey we carry out assesses three elements independently before arriving at a recommendation:
- Tile or slate condition: Is failure isolated — a handful of slipped tiles, a broken ridge — or systemic, meaning nail sickness has progressed across the majority of the roof?
- Underlay condition: Visible from the loft space. Original non-breathable bitumen felt from the 1960s–80s typically becomes brittle and begins to crack after 25 to 35 years. Once it crumbles when touched, it is no longer providing meaningful secondary waterproofing.
- Batten condition: Timber battens that have absorbed sustained moisture through failed felt develop a soft, darkened, delaminating character. Sound battens are hard and pale. Rotted battens cannot hold nails and will not support a re-tile without replacement.
If only one of these three has failed, repair or targeted replacement is almost always the right economic answer. If two have failed, we model the five-year cost comparison. If all three have failed, replacement is the only rational decision regardless of the apparent condition of the tiles from the outside.
NFRC guidance frames the repair-versus-replace decision around the condition of fixings and underlay, not just the visible tiles — widespread nail sickness typically tips the balance to replacement.
— NFRC technical guidance
The Five-Year Cost Model
When the decision is not clear-cut — typically when nail sickness is moderate (20 to 40% of tiles affected) and the felt is degraded but not fully failed — we apply a five-year cost model:
| Scenario | Year 1–5 Costs | Year 6–10 Projection | 10-Year Total |
|---|---|---|---|
| Repair and defer | £1,500–2,500 (ongoing repairs) | Re-roof at £7,000–9,000 | £8,500–11,500 |
| Re-roof now | £6,500–9,000 | Maintenance only £500–800 | £7,000–9,800 |
In most cases where two of the three elements have failed, the 10-year cost of re-roofing now is lower than the 10-year cost of repair-and-defer. The crossover point is typically around year four to six of the repair cycle.
Nail Sickness: The Repair Threshold
Nail sickness is the most common replacement trigger on Warwickshire's post-war estate stock. Our empirical threshold, based on years of Stratford area surveys:
- Under 15% affected: Targeted repair. Replace affected tiles with new stainless-nailed tiles. Economic and sufficient.
- 15–30% affected: Borderline. Model the five-year cost. Repair is defensible if the felt is sound; replacement is often better value overall.
- Over 30% affected: Replacement. Ongoing repair costs exceed replacement over five years in every Bridgetown and Clopton property we have assessed in this condition range.
- Over 50% affected: Replacement without question. You are already beyond the economic repair threshold.
When a Good Repair Is Better Than a Cheap Re-Roof
This is the scenario that is genuinely underserved in advice. A property with isolated tile failure, a sound felt underlay from a 1990s re-roof, and good batten condition does not need a re-roof regardless of how insistently a roofer recommends one. We carry out targeted repairs on sound roofs regularly and will always recommend this if the underlying structure supports it. A roofer who quotes a re-roof without going into the loft space to assess the felt and batten condition has not done an adequate survey.
The Honest Commercial Reality
A re-roof generates significantly more revenue than a repair. We have a commercial incentive to recommend replacement. We counter this by making the survey methodology explicit — felt and batten condition assessment is part of every visit — and by the practical reality that a homeowner who has been advised to spend £8,000 unnecessarily will not recommend us. Our business runs on recommendation, and honest repair-versus-replace advice is how we maintain it.
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