A roof or cladding system is described as nail sick when the slates, tiles, or boards are slipping because the nails holding them have severely corroded or degraded. The roofing material itself might still be perfectly sound, but the failure of the mechanical fasteners means the entire assembly must often be stripped and refixed. It is common in older slate roofs installed with iron rather than copper or galvanized nails.
Heard on the job
The slates are sliding off the lower courses because the whole elevation is nail sick.
Insider tip
When inspecting an old slate roof, push up gently on a few slates; if they slide easily, the roof is likely nail sick and requires a full tear-off.
Also heard as
- nail sickness