What is the average lifespan of a slate roof in the UK?

Lifespan figures for slate come from cost guides and trade publishers, and they agree on the broad picture. The Confederation of Roofing Contractors (CORC) reckons well-maintained slate can last 100 years or more. Checkatrade's slate guide says stone slate can last beyond a hundred years. By comparison, Marley expects concrete tiles to last around 60 years, while stressing that this promises nothing.

Read each as a typical span for a roof that went on properly and has been kept up. None is a promise about your roof, and the warranty on a job is a different matter from the life of the material, because a warranty covers workmanship for a set number of years and says nothing about the stone. A roof a century old is not on borrowed time simply because of its age, while one laid badly can fail in a fraction of that.

Slate is hard stone that sheds water and does not rot. What gives out first can be whatever holds it up: the nails or hooks, the battens, the underlay, the lead flashings and the ridge. A slate that slips has often come away from its fixing rather than broken. When a roof starts shedding slates in every storm, the fixings are telling you something about the whole slope, not only the pieces that have fallen.

That is why age alone does not settle a re-slate. A roof can have slates with decades left and fixings that have worn out, and the right job is then to strip the slates, renew battens, underlay and fixings, and relay the good ones. Our guide to re-slating a roof describes how that goes. The same slates, reused with new fixings, can carry on, and that is often the smaller and more sensible job.

Some slates are poor from the start, and others become so. Delamination, where a slate splits into layers and flakes, weakens the stone and is a quality issue, which our delaminating slates page explains. Treading on the roof breaks slates, and so does a pressure washer or an unsecured ladder. Blocked gutters and failed lead let water into the roof structure and rot timber that sits under perfectly sound slate.

Pitch and fixing matter too. Cupa Pizarras, summarising BS 5534:2014+A2:2018, advises against hooks below a 25 degree slope. A slate roof built too shallow, or fixed the wrong way for its exposure, will not reach the ages printed in a guide. Sea weather near the coast is hard on any roof, so a gale-damaged ridge or verge should be put right quickly, before it lets rain in behind the slates and starts to damage the timber.

You can learn a good deal from the ground. Look for slipped, missing or cracked slates, a dip in the line of a slope, a sagging ridge, stained ceilings or damp patches in the loft, and slates with flaking or crumbling edges. A few slipped slates after a storm are a repair. Many slipped slates across one slope, or slates that crumble when touched, suggest the fixings or the stone itself are failing.

A survey from the roof adds what the ground hides. We photograph the slates, battens, underlay and flashings and then say which of three jobs fits: a mend, a stopgap patch, or relaying the roof. Our guide to the signs a slate roof is failing lists what to check. Where the roof still has life in it, slate roof repair is the cheaper route, and often the right one.

A slate roof reaches its published age by being left alone and looked at after bad weather. Keep the gutters clear, keep off the slates, and have loose or cracked ones dealt with when they appear, because a single gap can let water to the timber beneath within one wet week. Lead flashings and ridge details are worth checking at the same visit, since they wear out sooner than the slate they protect.

Buying a house that has an old slate roof? Ask for a roof survey as well as the building survey, because a roof that needs re-slating is a major cost. Our new slate roof cost guide shows typical UK figures so you can plan ahead. Our own price follows the visit, in writing and as one sum, built on what the photographs show. For the wider picture, see the slate roofing page.

A roof on its last legs rarely fails all at once. It gives warning in small ways first, such as a stain on a ceiling after wind-driven rain or a slate found on the lawn, and catching those warnings is what keeps a repair small.