Question answered
How long do fibre cement slates last?
The short answer
There is no single dependable lifespan for fibre cement slate. It turns on the product and the year it was made, the exposure, the fixing and the upkeep, and a maker's warranty is not a lifespan. Natural slate is published at 80 to 100 years or more, while man-made slate is judged on its condition. Slates made before 2000 may contain asbestos.
Fibre cement slate is a man-made slate, and its lifespan depends on the product, its age, the exposure and the upkeep. It is also the type most likely to raise an asbestos question on an older roof.
Why one number misleads
Natural slate lifespans are easy to quote. MyBuilder talks of 80 to 100 years or more, and Checkatrade says most easily last over 100 years. Fibre cement slate is a manufactured board of cement and reinforcing fibre, pressed and cut to look like slate, and its life depends on which product it is.
The slates sold today differ from those laid in the 1960s and 1970s. Fixing quality, the type of reinforcement, the roof's exposure and whether the roof was ever cleaned or repaired all change the outcome. A warranty from the maker tells you what they will stand behind, which says little about service life.
So we judge a man-made slate roof on its condition. The survey looks at the whole roof and the photographs show what we find: what shape the slates are in, how they are fixed, and how much life remains.
Signs a fibre cement slate roof is ageing
Surface growth is the first sign. Moss and lichen sit on the slate, hold moisture against it and slowly roughen the surface, particularly on a shaded slope. They are not a fault by themselves, but a roof left untouched for decades usually shows more of it.
Edges tell you more. Look for flaking at the bottom edge, a layered look where the slate is splitting, or corners that have snapped off. Slates that crack when stepped on, or that break when lifted for a repair, are a poor sign. Man-made slate becomes brittle as it ages and does not always take a second fixing hole.
Nail holes and fixings matter too. Rust staining around a nail, a slate that has slid down or a slate that rocks tells you the fixing is failing. Fixing problems are covered in our page on why slate roofs leak. A few failed slates can be replaced; slates failing across a whole slope point to a re-roof.
Asbestos in older fibre cement slates
Some older fibre cement used asbestos as its reinforcing fibre. For anything built or refurbished before 2000 the HSE says to presume asbestos is there, and it names asbestos cement items such as roof sheeting among the usual places. A fibre cement slate from that era should be treated as suspect until tested.
The HSE puts careful removal of asbestos cement, without breaking it up, in the non-licensed category, even when the material is weathered. Once it is badly damaged or crumbling, the work becomes notifiable non-licensed work. It also calls such roofs permanently fragile and says pieces are lowered to the ground, not dropped or sent down rubble chutes.
Householders should leave it alone: do not drill, scrub, brush or pressure-wash these slates. Asbestos waste from a home is consigned by the removing contractor with a consignment note, in sealed, labelled wrapping. Asbestos insulating board, found in some old soffits, is mostly work for licensed firms. Testing a sample settles what you have before any decision.
Ridges, fittings and repair choices
A man-made slate roof is repaired differently from a natural one. Spare slates of the same make may no longer be sold, and lifting a brittle slate to slide a new one in can crack its neighbours. Where the roof is sound, individual slates and fixings can be replaced, and where it is not, a full re-cover is cleaner than a patchwork.
Ridges follow the same fixing practice as on natural slate: ridge tiles are clipped or screwed down as well as bedded. The options are set out in ridge tiles on a slate roof.
If the building is listed, man-made slate in place of natural slate may be judged a non-matching material, with the council deciding. Conservation-area homes have their own rules, covered in slate roofs in conservation areas. Put the question to the Adur & Worthing planning team before ordering any slate at all, natural or otherwise.
Repair, or a full re-cover
The decision rests on proportion and on what is under the slates. A roof with a handful of cracked slates and sound fixings needs only repair. One whose surface is flaking, whose nails are rusting and whose slates break when touched is nearing the end of its useful life. The wider question is set out in repair or re-slate.
If the slates are asbestos cement, a re-roof means careful removal, a different waste route and extra cost. For scale only, MyBuilder gives an average of around £2,000 for asbestos removal in general, and a house roof is set by its size and access. A survey and a written total follow before any decision. You can also compare natural slate on slate roof lifespan, and the rest of the topic sits under slate roofing.
Man-made slate: two more questions
Is there a way to know if my slates hold asbestos?
Not by eye. The HSE warns that buildings from before 2000 may contain it and that lookalike products without asbestos are hard to distinguish. A sample tested by a laboratory settles it. Do not take samples yourself by breaking or drilling a slate.
Can fibre cement slates be cleaned to extend their life?
Gentle cleaning of a sound roof can remove moss, but pressure washing can damage the surface and drive water under the laps. If the slates are old enough to contain asbestos, cleaning is not a job to attempt. We look at the condition first and say whether cleaning is sensible at all.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.