The short answer
Slates usually slip because the nails holding them have corroded or snapped, because the slate has cracked at its nail holes, or because wind has lifted a loose one. A single slipped slate is usually repaired with a tingle, a hook or a fresh slate on new fixings, where it can be reached safely. Several in one place point to a wider fixing problem and need a survey.
What holds a slate on, and what lets go
Most slates hang from two nail holes near the top edge, with the nails driven into timber battens. The slates in the course above overlap the nail heads, so the fixings are hidden and protected from rain. Nothing else secures the slate. The nails alone carry the load, season after season, through wind, frost and the slow movement of the timbers beneath.
When a nail fails, the slate may not fall at once. It can hang by its remaining nail, rattle in a gust and slide a few centimetres, leaving a gap that lets water in behind the course. That is the slipped slate. Its cause lies in one of a few places, and working out which one is the first step of any sensible repair, because a fix that ignores the cause will be undone by the next storm.
The usual causes of a slipped slate
Nail fatigue. Where the fixings are iron, rust works at them for decades until they snap or pull through the slate. It is a common cause on older roofs, and our answer on nail fatigue explains how it spreads.
A broken slate. A slate cracked across its nail holes, whether by frost, a footstep or a fallen branch, can no longer be held, so the lower part slides away.
Wind lift. A slate with a weak fixing can be raised and dropped back out of position by a gust, especially along verges, ridges and eaves where the wind catches the edge of the roof.
Movement and decay. Rotting battens or a sagging slope loosen the fixings. Slipped slates in a straight line along one course often mean a batten has softened at that height.
Some of these explain one slate, and some are the first sign of many. Telling the two apart is a big part of what a roofer is doing on the ladder.
How a single slipped slate is fixed
The choice depends on whether the slate is sound and whether the old nails can be reached.
Tingle
The simplest method uses a small metal clip cut from lead or copper sheet, screwed or nailed to the batten, its free end turned up across the tail of the slate to hold it. It is quick and suits a sound slate. See what a tingle is and where it stops working.
Hook or clip
A slate hook is a metal clip fixed to the batten that grips the lower edge of the slate. It suits a replacement slate where the old nails are out of reach. Cupa Pizarras says hooks should not go on any pitch under 25 degrees, so the roof's slope decides whether a hook is an option.
Renailing or replacing
Where access allows, a broken slate is cut out using a slate ripper, a flat steel blade with barbs that hooks the old nails and cuts them. A sound or new slate then goes in on fresh nails or a hook. MyBuilder's 2026 guide gives £60 to £120 as the national range for one slate. Cost mostly comes from getting to the spot, since the slate is cheap beside the ladder or scaffold needed to reach it.
When it is more than one slate
One slate out of place is a repair. Several slipped in the same patch, or new ones appearing after each repair, is a different story. It usually means the nails across that area are going, and mending them one by one, with separate access each time, soon adds up. For five to ten slates the same guide gives £150 to £350, a figure that assumes the surrounding roof is sound. If it is not, the number is only a starting point.
On the survey visit we read the pattern of gaps from outside and again from the loft, then photograph the slope for your records. Slipped slates in a patch sometimes sit beside a cracked ridge or a dropped valley lining, and we note those too, because one repair can mask another. Our guide to slate roof repairs in Stroud follows the options from a single tingle to renewing a whole slope.
If the gap is above a lane, a terrace or a steep garden, say so when you call. Access is worked into the written quote and not discovered afterwards.
Leaving it, and doing it yourself
A slipped slate leaves the underlay and battens exposed. Even a thin slot, hard to see from the garden, can soak the timber beneath over a wet winter. Calls about water coming in, and about slates lost in a gale, go to the head of our queue, and the first visit is about stopping the damage. Slipped slates after a gale are a typical reason for that call.
Please keep off the slates. Slate is brittle underfoot, and a ladder leant against it can crack the very slates you are trying to protect. Boards or a roof ladder spread the weight, which is part of why we plan access first. If you can see the gap from a window or the garden, a phone photograph is a useful starting point for us. Repairs we do carry a written workmanship guarantee of 10 years. The bigger picture lives under slate roofing in Stroud, and 01453 933613 reaches us if you would like a look at yours.