Slate roof repair for slipped and cracked slates

Natural slate itself lasts a very long time. What gives way first is usually the fixing. Each slate hangs from nails, and over decades those nails rust through in the damp, salty air that blows in off the Forth and the Tay. When a nail fails, the slate slides down the slope, leaving a gap that lets rain onto the sarking or felt beneath. Builders call this nail fatigue, and it tends to show up as one or two slipped slates at first, then more each winter.

Slates also crack. Someone walking on the roof, a falling branch, a ladder leant against the eaves or simple frost working into a flaw can split a slate across its face. A cracked slate may stay in place for years while quietly letting water through the break.

A slipped slate may leave a dark gap visible from the ground, expose felt or sarking, or appear in the garden after wind. The slate itself can remain intact while its fixing has failed. We check the neighbouring courses as well as the obvious gap, since nearby nails may be at a similar stage of wear.

A repair involves safe access, lifting or securing the slate appropriately, and checking the layer beneath for signs of water entry. Avoid walking on slate or trying to push a slate back into place; fragile coverings can break and wet roofs are hazardous.

A handful of slipped slates on an otherwise sound roof is a repair. A roof where slates are slipping across every slope, where nails are rusted through in many places and where earlier repairs are held on with tingles or sealant is a different picture. Patching that kind of roof means paying for access again and again while the problem spreads.

Re-slating involves stripping the slates, renewing battens and membrane and re-hanging the roof, reusing sound slates where possible and making up the rest. It is a bigger decision, covered in more depth on our roof replacements page. We will tell you plainly which side of that line your roof sits on, and why.

Slate roof life expectancy is not determined by the stone alone. Natural slate can remain serviceable for a long time, while nails, battens, underlay, flashings and ridge details may need attention earlier. Exposure, workmanship, ventilation and maintenance all influence condition, so there is no reliable single lifespan for every roof.

When asking how long does a slate roof last, consider whether failures are isolated or recurring across several slopes. A roof with sound slates but tired fixings may be repaired or re-slated selectively; widespread slipping, brittle underlay or repeated leaks can indicate a more extensive project. Our natural slate types and re-slating pages explain the material and renewal options. The minimum angle for slate roof guide covers pitch limits, and our slate roofing in Edinburgh page discusses local roof work.