What people mean by nail sickness
The term commonly refers to corrosion or deterioration of slate fixings that allows otherwise serviceable slates to loosen and fall. Fixings are only one part of a traditional roof system. Age alone does not establish failure, and an isolated slipped slate does not prove widespread deterioration.
Warning signs that justify an inspection
- Recurring slipped slates on multiple slopes rather than a single isolated slip
- Repeated repairs that do not stop new slates loosening
- Water penetration after ordinary weather, particularly around laps or junctions
- Visible patch repairs, poorly matched fixings or broken slate corners
- Moisture or timber staining in roof voids where accessible and safe
Some symptoms can also arise from wind damage, poor previous installation, weak slate, movement or flashing problems.
How a professional distinguishes the causes
A suitable roofing professional may inspect patterns of failure, slate condition, fixing type, vulnerable details and underlying timber fabric, using safe access. On a listed or otherwise complex roof, a conservation specialist may need to advise on retention, sampling and repair methods. Avoid climbing on slate yourself: traditional coverings are easily damaged and work at height is hazardous.
Repair individual slates or consider broader re-slating?
Localised problems often merit targeted repairs. Where the fixing system is failing throughout large roof areas, replacing individual slips repeatedly may not solve the underlying issue. A condition-led assessment should evaluate whether full or partial re-slating is more sensible, the quantity of reusable sound slate and the impacts on leadwork or timber details.
For the cost factors of larger works, see our slate replacement cost guide.
A practical owner action plan
- Record where and when slips occur, from ground level only.
- Arrange safe professional investigation if problems recur or water enters.
- Check whether the building is listed or otherwise subject to restrictions.
- Ask for written recommendations distinguishing cause, repair scope and uncertainty.
- For a substantial project, obtain comparable specialist quotations.
SSR can help with step five for eligible substantial traditional-roof projects. We do not carry out the inspection or confirm a diagnosis.
Frequently asked questions
Can nail sickness be confirmed from a photograph?
Usually not reliably. Photographs can show symptoms but not the condition of concealed fixings across the roof.
Does nail sickness mean every slate is beyond use?
No. Depending on condition, sound slates may be suitable for careful recovery and reuse during re-slating.
Is one missing slate an SSR project?
Normally SSR focuses on substantial roofing projects, not small routine repairs. Prompt local repair advice may still be appropriate.
Further guidance and sources
These independent references explain official repair categories, maintenance and consent considerations. SSR does not claim their endorsement.