Fibre cement slate: thin, brittle, and worth cleaning carefully
Fibre cement slates were fitted on a huge number of homes from the 1960s through to the 1990s as a lighter, cheaper alternative to natural slate, and they are thinner and more brittle than most people assume. A tile that looks like slate does not behave like slate under a boot or a pressure lance.
These roofs green up in exactly the same way as any other, but the margin for error while cleaning them is smaller, because a cracked fibre cement slate is a genuine repair rather than a cosmetic mark.
Why fibre cement needs a lighter touch than it looks like it does
Fibre cement slate is manufactured thin and flat, without the natural grain variation of quarried slate that gives it some resilience. Decades of weathering also make older fibre cement more brittle than it was when fitted, so a roof that looks structurally fine can still crack under a point load that a natural slate roof would shrug off.
Our approach
- Hand brushing and scraping only — no pressure washing under any circumstances on this covering.
- Roof ladders to spread any load where walking the roof is unavoidable.
- Biocide treatment applied to slow regrowth rather than relying on repeat aggressive cleans.
- Any cracked or slipped slate flagged before we continue working near it.
A note on older fibre cement products
Some fibre cement slates fitted before the 1980s contain asbestos. We do not test for this or disturb suspect material, and where a roof's age or condition raises the question, the right step is a specialist survey before any cleaning takes place — not something we can assess by eye alone.
Our own photographs
Images from Sky Scrapers Ltd work showing the methods described on this page.
Where this applies locally
Towns where this comes up most often on our patch:
- Hand Roof Cleaning in DunstableBedfordshire · LU5
- Hand Roof Cleaning in LutonBedfordshire · LU1
- Hand Roof Cleaning in Houghton RegisBedfordshire · LU5
- Slate roofsRoof covering
- Crusty lichen on roof tiles and why it is harder to shift than mossCommon problem
- Period and listed property roofs cleaned entirely by handBuilding type
Questions we get asked
Are all fibre cement slates the same?
No. Products and formulations changed considerably between the 1960s and 1990s, and condition varies a lot with age and exposure. We assess each roof rather than assuming.
Could my fibre cement roof contain asbestos?
Older products can. We do not test for this ourselves, and if there is any doubt about a roof's age or composition, a specialist survey should happen before any cleaning work.
Is fibre cement more fragile than natural slate?
Generally yes, particularly as it ages. It has less natural resilience to point loads, which is part of why we always use load-spreading access rather than walking directly on the covering.
Will treatment slow down how quickly it greens up again?
Biocide treatment after cleaning does slow regrowth, though the interval depends heavily on shade and aspect.
Ask about a fibre cement roof
Let us know roughly when the roof was fitted, if you know, and send a couple of photos so we can advise properly before quoting.
Sky Scrapers Ltd · info@sky-scrapers.co.uk
In short
Fibre cement slate looks tougher than it is. Hand cleaning, load-spreading access and honest flagging of any condition concerns are non-negotiable on this covering.