Why do slates slip, and how are they refixed?

A slate hangs by its nail or hook, and gravity pulls on it all day. Nothing about the stone makes it slip; the fixing gives way first. A steel nail passing through the slate rusts over the years, thins, and either snaps or lets the slate drag over the shank. The slate then sits a little lower than its neighbours, and the next gust finishes the job.

The nail hole matters as well. A hole that was punched too near the slate's edge, or has been widened by movement, leaves little stone for the nail to bite on. Add a heavy fall of rain, a gale from the sea, or a frozen spell that swells moisture in the stone, and the weakest slates drop first. Look from the ground and you may see a slate poking out at an odd angle or a dark gap where one has gone altogether. A gap is a route for water, so it counts as a leak waiting for the next downpour.

Roof shape plays a part. Marley points out that a slope under 30 degrees can see strong negative pressure on its windward side, lifting coverings instead of pressing them down. Slates laid near the minimum pitch therefore lean hard on their fixings. Cupa Pizarras advises against hooks below 25 degrees, so a hooked slate on a low roof is a mismatch we watch for.

Exposure is local and specific to each house, which is why fixing specifications are set per site, using location, altitude and wind exposure. So we read the roof in front of us: how high it stands, which side faces open ground, whether the eaves and verges are sound, and what was used to fix the slates. Our page on slate roof storm damage covers what a gale does to a slate slope.

For a lone slipped slate on a sound slope, the fix is quick. The slate is slid back or replaced, and a tingle holds it. A tingle is a metal strip nailed to the batten and folded over the slate's tail, and our page on slate tingles describes it in detail. Slates beside the repair are checked by hand to see whether they have the same weakness.

If several slates in one area have moved, the sensible repair is a section. The affected courses are lifted, the slates with broken or enlarged holes are discarded, sound ones are re-holed or re-fixed, and the section is laid back to the original gauge. Fixings are chosen for the pitch. Where the whole slope is slipping, patching is wasted effort, and the photographs show why. That is when a re-slate, in part or in full, becomes the sensible answer, and the survey explains why before any number appears.

One slipped slate is an event. Slates slipping in different places over the months is a pattern, and the pattern has a name, nail sickness. Our guide to nail sickness sets out how it is recognised. The telltales are slates sitting low, bright tingles from earlier mending, and small pieces of broken slate collecting in the gutter.

It helps to be realistic about what a repair buys. A mend restores the slates around it, and the rest of the roof keeps ageing. We often recommend repairing now while keeping a record of what each visit found, so that later you can see whether the problem is spreading. That record is also what you would show an insurer, or a surveyor if you sell. Slate has the reputation of lasting a century or more, and CORC does say well-maintained slate can last 100+ years. Maintenance includes noticing the fixings. For the wider picture of repair and re-slating, see our slate roofing page, which links each job to its own guide.

Checkatrade's roof repair table, updated in 2026, shows natural slate repair at £150 to £220 per square metre, excluding VAT, and slate roofers at £280 to £360 a day. Treat those as national guide figures, never as a JJ price. What shifts the real number is access (a ladder or a scaffold), how many slates need replacing, and what the survey finds under them. The written quote follows the visit.

Until then, keep off the roof. Slate cracks beneath a boot, and a tumble from a ladder is a bigger danger than a leak. Check from the ground, stand clear of the eaves in wind, and put a bucket under any drip. If a gale did the damage, tell your insurer first, photograph what you can see, and keep receipts for temporary work. Which? gives the same guidance and adds that a leak through a neglected roof can be dismissed as ordinary ageing.