A slate stays on a roof because of something small: two nails, or a pair of hooks, or a hook and a nail working together. Choose the wrong fixing and the roof can look perfect for ten winters and then start dropping slates in the first hard gale. Slate hooks and nails are both used on good roofs, and each has a place. The question is which suits the slate, the pitch, the exposure and the repair history of the roof in front of you. This page compares the two methods, explains the materials they are made from, and sets out how a roofer decides.
How a slate is held on
A slate hangs from a timber batten and is overlapped by the slates above it. Water runs down the face of each slate and is shed by the one below, so the job of the fixing is not to hold water out but to keep the slate from sliding, lifting or rattling loose. Two forces try to move it. Gravity pulls it down the slope, and wind lifts it, sucking at the tail like a flap. A good fixing resists both.
With nailing, two holes are made in the slate, usually near the top third (called head nailing), or around the middle (centre nailing) on some traditional roofs. Nails go through the holes into the batten, and the slate hangs on them. With hooks, the slate has no holes. A stainless steel hook is fixed to the batten and bends round the bottom edge of the slate, holding the tail down against the slate below. Both methods are accepted practice. Each has a different failure pattern.
Nails: how they work and where they fail
Nailing is the traditional method and the one most slate roofs are fixed with. Each slate has two holes. The nails are driven into the batten just tight enough to hold the slate, not hard enough to pinch it, because a slate fixed too tightly cannot move with the batten as the timber shrinks and swells, and it cracks.
The strengths of nailing are simple. It is quick and proven, nail holes are punched or drilled in factory-prepared slate, and a nailed slate is held by the batten at the top, where the weight is carried. The slate hangs and does not need its tail clamped. On a sheltered, steep roof laid in good Welsh slate, nailing is hard to improve on.
The weaknesses are about what the nail is made of and how the slate was holed. Iron or galvanised steel nails rust, and rust swells and snaps them. Many of the slipped slates on old roofs are the result of this, with slates dropping because the nail has corroded through. Soft or poor nails bend. Holes punched too close to the edge split, and a slate nailed through a split slides as soon as the nail eases. Our guide to slipped and cracked slates goes into those causes.
What nails to use
Copper and stainless steel are the right materials. Copper nails are traditional, easy to work and resist corrosion well. Stainless steel is harder and lasts longer in aggressive conditions, such as coastal air or industrial areas. Both are used with slates in the Basingstoke area, and both outlast the old iron and galvanised nails by a huge margin. Aluminium nails are sometimes sold for slate, but they can corrode in contact with certain mortars and lime, and we avoid them. Whatever the material, nails must be long enough to bite properly into the batten and have a head wide enough not to pull through.
Hooks: how they work and where they help
A slate hook, sometimes called a hook fixing or tail fixing, is a stainless steel clip. It is nailed or screwed into the batten and curves up round the bottom of the slate, or clips over its lower edge. Because there are no holes, the slate is not weakened by drilling, and the hook holds the tail down in strong wind. It also lets the slate be changed without ripping nails out.
Hooks are used in three situations. The first is exposure: on a roof in a gale-prone spot, a nailed slate can lift at the tail, and a hook keeps it held. The second is thin or large-format slate, which is more likely to crack when holed. The third is repairs. A slipped slate can be re-secured with a copper strip, known as a tingle, or with a hook, without disturbing neighbouring slates. Our page on what a slate tingle is explains that repair, and how a single slate is replaced describes the full job.
Hooks have downsides. They are more visible, since a bright stainless clip can show at the tail of the slate. They add cost and fitting time. A badly made hook can also hold the slate too rigidly, or damage it by pressing on the edge. On a roof where the slate is thick and the fixings are doing their job, hooks may be unnecessary.
A direct comparison
| Point | Nails | Hooks |
|---|---|---|
| Method | Two holes through the slate, nailed to the batten | Stainless clip on the batten, holding the tail |
| Slate holed | Yes | No |
| Wind resistance | Good on sheltered sites, helped by a tail clip on exposed ones | Strong at the tail |
| Appearance | Nothing visible | Clips can show |
| Best for | Standard slate on sheltered, steep roofs | Exposed sites, thin slate and some repairs |
| Typical weakness | Corroded or poorly placed nails | Cost and visibility |
How a roofer chooses
The decision rests on five questions.
How exposed is the roof? A house on an open ridge, or on a hillside facing the prevailing south-westerlies, sees more uplift than one in a sheltered street. Exposed roofs benefit from a tail fixing, whether a hook or a clip, alongside the nails. How steep is the pitch? On shallower pitches, water is driven further up under the laps, and the slates need to be held firm. What is the slate like? Thin or fragile stone is best left unholed. What is the roof's history? If slates have been lifting in storms, it argues for extra security. And what do the manufacturer's instructions or the local guidance say? Good practice follows the product, the standards for slating and the conditions on site.
In practice, the most common answer is nails in copper or stainless steel for the body of the roof, with extra fixings at the eaves, verges, hips, ridge and any slates that are cut short. The eaves and edges see the highest wind loads, so they get more attention. On exposed sites we add hooks or clips across the field.
Head lap, gauge and why the fixing position matters
A slate roof keeps water out through overlap, not through the fixings. Each course covers the joint between the slates beneath it, and the amount by which a slate overlaps the one two courses down is the head lap. A bigger lap means more protection from driven rain and snow, and it is increased on lower pitches and in exposed places. The gauge is the distance between batten centres, worked out from the slate length and the lap, and the fixing position follows from it.
This is why a fixing cannot be treated as a detail. A nail hole punched too high weakens the slate where it is most stressed, and one punched too low lets the tail flap. A hook sized for one slate thickness can sit too loose or too tight on another. If the gauge is wrong, the holes do not line up with the batten, and the roofer is tempted to nail at an angle or miss the timber altogether. Our guide to head lap on a slate roof explains the geometry. When we price a re-fix, the gauge and the lap are worked out first and the fixing method second.
Warning signs that a roof has the wrong fixing
You do not need to be a roofer to spot the pattern. Slates dropping in gusts but not in still rain suggest a tail-lift problem, where nails alone are not holding against wind. Slates that slide straight down, leaving their nails behind in the batten, point to broken or corroded nails. Slates that crack across the hole line suggest nails driven too hard or holes punched too close to the edge. Rust marks running down the slate face from each hole point to iron fixings that will soon fail.
Look on the ground too. Snapped nail shanks in the gutter or among the gravel are not a good sign either. The same is true of slates that have slipped about a hand's width and then stopped, hanging by the nails still in the batten. In that case the nail on one side has gone, and the other is likely to follow.
Fixing, ventilation and the rest of the roof
Fixings do not work in isolation. A nail driven into a rotten batten has nothing to grip, and a hook on a batten that is the wrong thickness will not sit properly. The battens must be sound, correctly spaced and the right size for the slate, and the underlay beneath must be in good order. Our guide to underlay and ventilation on slate roofs shows how the layers beneath keep the battens dry and the fixings working.
Ridge and hip fixings are a separate matter. These components are fixed mechanically to British Standard BS 5534:2014, which does not rely on mortar alone, so even a traditional bedded ridge is now secured with stainless fixings. The same logic applies at the verge.
Getting the right advice on your roof
If your roof is losing slates, the question is whether the fixings are failing or the fixings are the wrong type for the site. A survey with close photographs answers that. We note the nail material where we can see it, check for corrosion at the tails, look at how exposed the slopes are, and report back with a written recommendation. A repair with hooks or tingles is often the cheaper answer when the slates themselves are sound. A full re-slate with the correct fixings throughout is the answer when the nails are going across the board.
You get a fixed price in writing, the work is backed by our ten-year guarantee on workmanship, and the waste goes with us. For the rest of our slate work, see slate roofing in Basingstoke, or get in touch by WhatsApp or on 01256 213956 to arrange a visit.
