Nail sickness is the corrosion of the iron nails fixing roof tiles or slates, causing them to lose grip so tiles slip in high wind. It affects most Scottish post-war roofs at 50–70 years old. A nail-sick roof usually needs full re-roofing rather than repair, costing £5,000–£9,000 in Perth.
Nail sickness is the single most common cause of full roof replacement on post-war Scottish housing, and it is poorly understood by most homeowners. A nail-sick roof can look perfectly normal from the ground — tiles in place, no obvious damage, no visible leaks — while being genuinely unsafe in any significant wind event. This guide explains what it is, how to spot it, and what to do.
What Causes Nail Sickness?
When concrete interlocking tiles, clay tiles, or natural slates are fixed to a roof, they are nailed or clipped to timber battens. On properties built before the 1980s, the nails used were typically iron or low-grade steel without corrosion protection. Over decades, these nails corrode — slowly at first, then accelerating as moisture from the roof space and the external environment attacks the metal.
Once a nail corrodes sufficiently, it loses its grip on the tile or slate above it. The tile is then held in place purely by its own weight and the friction of adjacent tiles. In most conditions this is fine. In strong wind, it is not. A gust that would leave a correctly-nailed roof intact can lift sections of a nail-sick roof cleanly away.
On the post-war estates in Letham, Tulloch and Muirton, the iron nails used in 1950s–60s construction are now 60–70 years old.
At this age, corrosion is near-universal on unprotected iron fixings. The question is not whether nail sickness is present, but how extensive it has become.Iron roofing nails used before the 1980s have a typical service life of 40–60 years before corrosion causes nail sickness, according to NFRC technical guidance on fixing specification and BS 5534 (the British Standard for slating and tiling).
Source: NFRC technical guidance / BS 5534
How to Check for Nail Sickness
The definitive test is a loft inspection. From inside the roof space, tiles or slates that are nail-sick can often be moved by hand pressure from below — they rock or lift without the resistance a correctly-nailed tile provides. A torch across the underside of the roof deck may also reveal light coming through where tiles have shifted slightly out of alignment.
External signs are less reliable but include: tiles or slates sitting slightly lower than their neighbours, sections that have slipped down the slope, and any ridge tiles that move when touched. Individual tile replacement calls that keep recurring on the same roof are another indicator — it suggests the fixing failure is spreading rather than being isolated.
Nail Sickness in Perth: Which Properties Are at Risk?
The highest-risk properties in Perth are those built between 1950 and 1975 with concrete interlocking tiles. This covers most of the Letham, Tulloch, Muirton and North Muirton estate housing. Victorian and Edwardian properties with original natural slate are also at risk from nail rot, though the timeline is different — original iron nails on a Victorian slate roof may have lasted 100 years before finally failing.
What to Do If You Suspect Nail Sickness
The first step is a professional roof survey. A thorough inspection from inside the loft and across the roof surface will tell you what percentage of fixings have failed and whether the deck and battens are sound enough to justify re-nailing or require full replacement.
If the survey identifies widespread nail sickness across a whole slope, the practical answer is usually a full roof replacement. Stripping the tiles to re-nail accounts for most of the labour cost of a full replacement anyway. For limited nail sickness affecting less than 20% of a slope, targeted re-fixing is cost-effective.
Suspect nail sickness on your Perth property? Book a free roof inspection.
01738 245 298 Book a Free Roof SurveyNail Sickness: A Perthshire Perspective
Nail sickness is not equally distributed across Perthshire. The post-war building programmes of the 1950s and 1960s created dense concentrations of nail-sick properties in specific areas. Letham, Tulloch and Muirton in Perth — built primarily between 1952 and 1968 — represent the highest-risk cluster in our service area. Blairgowrie's Rattray estates and Kinross's southern estates are the other significant concentrations. If your property is in one of these areas and was built before 1970, nail sickness should be the first thing you investigate.
The average concrete tile roof in Letham or Tulloch is now 60–70 years old.
Design life for the fixings on these properties was typically 40–60 years. Most are past it.Nail Sickness vs Other Roof Problems: How to Tell the Difference
| Problem | How it presents | Cause | Fix |
|---|---|---|---|
| Nail sickness | Tiles rocking or sliding; visible from loft inspection | Corroded iron nails losing grip | Re-nail (limited extent) or full re-roof |
| Mortar failure | Ridge or hip tiles loose; visible gaps in pointing | Mortar carbonation or frost cycling | Repointing or dry-fix replacement |
| Lead failure | Ceiling damp near chimney or valley; staining on chimney breast | Age, incorrect installation, frost damage | Lead replacement |
| Tile cracking | Visible cracks; water ingress at specific points | Frost damage, impact, or age | Individual tile replacement |
| Deck rot | Soft spots felt from loft; sags visible from outside | Persistent water ingress over time | Deck section or full replacement |
The Economics of Nail Sickness: Repair vs Replace
The financial decision on a nail-sick roof comes down to the percentage of failed fixings and the condition of the deck and battens beneath. Here is how we think about it at Perth Roofing Experts:
Under 15% failure, sound deck: Targeted re-nailing or re-clipping is viable. Budget £800–£2,500 for a slope in this condition. This buys 10–15 years if the rest of the structure is sound.
15–30% failure: The borderline zone. We weigh the labour cost of stripping to re-nail against the cost of a full re-roof slope. Often the difference is smaller than homeowners expect once access is accounted for.
Over 30% failure: Full replacement is almost always the right call. Stripping the tiles to re-nail accounts for the majority of re-roof labour cost anyway. Replacement battens, breathable felt, and a new tile specification will cost only 20–30% more than re-nailing alone, and deliver a 40–50 year design life.
Unsure whether your Perth roof needs repair or replacement? Book a free inspection.
01738 245 298What a Good Nail Sickness Survey Looks Like
A proper nail sickness assessment requires a loft inspection, not just a look from the ground. From inside the roof space, an experienced roofer can test individual slates or tiles by applying hand pressure from below — a sound tile resists firmly; a nail-sick tile moves or rocks. A systematic check across representative sections of each slope gives a percentage estimate for the whole roof.
We also check batten condition (rot or split battens need replacing regardless of tile state), deck integrity (soft spots indicate existing water damage), felt condition (original bitumen felt may be cracked and fragile), and the state of any valley or flashing work adjacent to the nail-sick area. The full picture determines whether targeted re-nailing or full replacement is the genuinely cost-effective option.
Common Questions
Look for tiles that slip after wind, a scatter of tiles on the ground, or tiles that rock when pressed from inside the loft. A professional loft inspection confirms it by testing fixing grip. In Perth, most 1950s–70s estate roofs are in the nail sickness window.
Nail sickness usually requires full re-roofing rather than repair, costing £5,000–£9,000 for a standard 3-bed semi in concrete tile. Where slates are sound and only the nails have failed, selective re-nailing can be cheaper. A free survey establishes which applies.
Occasionally — if the tiles or slates are sound and only isolated nails have failed, re-nailing or re-hooking can extend the roof's life. But where corrosion is widespread across the fixings, replacement is the only lasting solution. A survey determines the extent.
Yes. A nail-sick roof can shed tiles in high wind with no warning, creating a falling hazard and exposing the roof structure to water. It often looks normal from the ground, which is why it is dangerous — the failure is hidden until a storm reveals it.
Perth's large post-war estates at Letham, Tulloch, and Muirton were built in the 1950s–60s with iron nail fixings that have now reached the end of their life. Perthshire's damp climate accelerates the corrosion, putting most of this housing stock in the replacement window.
Usually not. Nail sickness is classed as wear and tear rather than sudden damage, so buildings insurance typically excludes it. Storm damage that results from a nail-sick roof may be partially covered, but the underlying replacement is normally the homeowner's cost.