A slate hook is the metal hook used to fix a slate on the roof. The hook is driven into the boarding or clipped behind the batten, and its turned-up foot passes over the tail of the slate so it cannot lift in the wind or slide down.
In hook slating the slate is therefore not held by a nail through the plate, but gripped at its tail by the hook belonging to the course below. Each slate is covered from above and held from below — a wind-resistant system in which individual slates remain replaceable.
Material
- Stainless steel is now virtually the only choice. It does not rust and has a service life in the same order as the slate itself.
- Brass is also used, on the same reasoning: non-rusting and not readily attacked.
- Copper was widely used from the 1930s until the early 1980s. In hindsight it proved the weak link: copper hooks generally last some twenty-five to thirty years, after which they are worn thin where the slate bears on them, or corroded through by acids dissolved in rainwater. On north-facing, persistently damp roof planes this happens fastest.
| Stainless steel | Now virtually the only choice; does not rust, service life in the same order as the slate itself. |
|---|---|
| Brass | Also used: non-rusting and not readily attacked. |
| Copper | Widely used from the 1930s until the early 1980s; generally lasts some twenty-five to thirty years, then worn thin or corroded through. |
| Galvanised steel | Never use: attacked within a few years in this application. |
Why it matters for maintenance
On an old slate roof the question is rarely whether the slates are still sound — natural slate lasts for generations — but whether the fixings are. Anyone seeing more and more loose and slipped slates on a roof from the 1960s or 1970s is almost always looking at failing copper hooks, not worn-out slate.
What follows from that:
- Loose slates come in waves. Once the first hooks fail the rest follow within a few years; at that point re-hooking the whole roof makes more sense than repeatedly refitting single slates.
- The slates can often be reused. In a re-covering, a large proportion of the natural slates can go back on, which saves substantially on materials and is in any case the appropriate solution on a historic building.
- Check from underneath. A hook that looks intact from above may be worn through behind the slate. An assessment by a slater tells you far more than a look from the ground.
Practical points
- Never use ordinary galvanised nails or hooks. Galvanised steel is attacked within a few years in this application, and replacing it costs you the whole roof.
- Do not mix metals. Copper hooks combined with a zinc gutter or lead flashings lead to accelerated corrosion; keep the metals in the roof plane compatible.
- Hook length must match the slate size. Hooks that are too short grip insufficiently; too long and they stand proud in view.
- Renovation work calls for a slate ripper. That is the tool for drawing out old nails and hooks beneath a slate in place, without breaking the surrounding slates.
Related terms
- Slate roof
- Roof slate
- Slate hammer
- Roof boarding
- Roof batten
- Roof pitch
- Corrosivity category
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