Question answered
Slate hooks or nails?
The short answer
Slates can be fixed with nails, or with hooks that clip the slate at the foot and hang from the batten. Hook fixing is quicker and leaves no holes, but Cupa Pizarras puts the floor for hooks at 25 degrees of slope. Nails suit shallow slopes, exposed sites and most conservation work, where the roof should look as it always has.
Slates can be held by a nail through the head or by a hook over the batten. Each suits particular roofs, and on the wrong slope, in the wrong setting, one of them is the wrong choice.
How a nailed slate and a hooked slate differ
On a traditionally fixed roof, each slate has a hole punched near its head, or its centre on some roofs, and one or two nails go through it into the batten. The nails sit hidden under the course above, and the slate is held by the shank passing through the stone.
A hook fixing turns that around. The slate is not drilled for a nail. Instead, a hook, usually a stainless steel or similar strip, is fitted to the batten and curves around the foot of the slate or its side, so the slate hangs from the hook rather than from a nail. The hook may be visible as a small metal tip at the bottom of the slate.
Both can hold a slate through years of weather. The wider choices for a slate roof sit under our slate roofing page. What differs is how they cope with wind, with the angle of the roof and with the look from the street. The same decision comes up when a roof needs re-slating after slates start to delaminate.
The 25 degree limit on hooks
Cupa Pizarras gives 25 degrees as the lowest slope for hooks. Set that against the 20 degrees Cupa takes from BS 5534 as natural slate's own floor, so there is a band of low-pitched slate roofs between 20 and 25 degrees where nails are the answer and hooks are not.
The reason is simple. On a shallow slope, the slate lies nearly flat and the wind can lift its foot, working it against the hook. A nailed slate is held at the head by the fixing and is less likely to chatter.
If you are told a low-pitched slate roof can be hook-fixed because it is quicker or cheaper, ask what the manufacturer's data sheet says for that slate and that pitch. Our page on the minimum pitch for slate shows how the headlap changes with the angle.
Appearance and conservation settings
From the ground, a nailed roof looks like a slate roof has looked for centuries: clean courses, no metal at the foot of a slate. Hooks can show at the bottom edge, and on some roofs they catch the light or cast a small shadow line. On a plain Victorian terrace that changes the look of the street.
In a conservation area, a planning officer or conservation officer may have a view on fixing, not just on the slate itself. We suggest asking your local planning team before any re-slate in a protected setting, and checking with them if the change would alter how the roof looks. For Worthing, that means the Adur & Worthing planning team.
Whether a particular listed or protected building can take hooks depends on its consents, and we cannot answer that for you. Where a roof is being relaid like for like, nails and the original slate size are usually the closest match to how it was built.
Speed, cost and what a roofer is weighing
Hooks are quicker to fit on a regular roof, and because the slates are not drilled, there is less breakage in handling. That can lower labour on a large, simple slope. Nails take longer, especially on a roof where each slate must be holed on site, but give a traditional result.
We recommend the right job for the roof, not the quickest one. On a steep, plain, modern slope, a hook system from the slate maker can be a sound choice. On a low, exposed or historic roof, nails earn their place.
Our quote is written after the survey, as one total, so ask what fixing sits inside it and what the fixing is made of. You also get photographs of your battens and slope, which show the pitch and condition behind what we recommend.
Looking after the fixings you choose
Whichever you pick, the fixing will outlast the slate only if the roof is kept dry and clear. Moss and trapped leaves hold water at the foot of the slates, and metal fixings fare worse on a roof that stays wet. Our guide to slate roof maintenance covers what a sensible routine looks like.
Cracked slates also need attention. A cracked slate is not only a leak risk; the piece that has broken free can pull at a hook or loosen a nail on the course below. The page on cracked slate repairs sets out the options.
Ask any roofer to put the fixing type, the headlap and the batten condition on paper. If a hook is quoted, ask for the pitch to be stated too, so you can set it against the 25 degree limit and ask the maker's sheet to confirm it.
Fixing choice: two more questions
Do hooks make a roof stronger in a gale?
Not by themselves. Strength comes from the right fixing for the slope, the headlap, sound battens and correct installation. A hook on a pitch where the maker says not to use one is weaker than a nail, not stronger.
Can nails and hooks be mixed on one roof?
They can be where a repair matches a slope already fixed one way, but it should be a considered choice. Mixing fixings across one slope can leave different parts behaving differently in wind, so the pitch and slate size need checking first.
Tell us about your roof
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