Suspect materials · slates
Are these slates asbestos?
Flat asbestos cement slates were used as a roofing material on Irish bungalows and outbuildings until the 1999 EU ban. They look similar to natural slate and to modern fibre-cement. Visual resemblance is not a diagnosis.
What asbestos cement slates are
Asbestos cement slates are a composite made of Portland cement and asbestos fibres, pressed into flat thin sheets. Eternit was a common brand. Used as a roofing tile in Ireland from the 1950s to the late 1990s.
What to look for
- Flat, smooth, uniform-thickness slates — typically 400 × 240 mm or 600 × 300 mm.
- Grey, but sometimes coloured — red, green or blue. Coloured slates are paint over the same cement composite.
- Hung with copper or galvanised nails or hooks, two per slate, sometimes with a small bottom rivet.
- Brittle — they crack rather than bend. Old slates may be cracked or broken from foot traffic, weather or impact.
- Smooth back face — natural slate has a rougher, fissured back.
Where they show up in Ireland
- Pitched roofs of bungalows and small outbuildings built between roughly 1960 and 1990.
- Re-roofs of older properties carried out in that era — sometimes installed on top of older felt or original slate.
- Some council and local-authority housing of the period.
Risk profile
Asbestos cement slates are bonded — non-friable when intact. The asbestos fibres are locked in the cement matrix and a sound, weathered roof in good condition does not release fibres at significant rates. Risk arises if the slates are:
- Drilled or cut.
- Walked on heavily, especially old brittle slates.
- Power-washed.
- Removed without proper controls.
If you have asbestos cement slates
- Don't walk on them carelessly. Old slates are brittle and breaking one releases fibres at the break.
- Don't power-wash. The pressure removes the bonded surface and washes fibres into runoff.
- Don't drill into them — for satellite dishes, solar mounts, anything.
- Get a survey if you are planning re-roofing, repair or any disturbance.
- Engage a permit-holding contractor for removal — see the roof removal guide.
Frequently asked questions
Are all grey slates on old Irish roofs asbestos?
No. Natural slate (the dominant traditional Irish roofing material) does not contain asbestos. Asbestos cement slates are a manufactured composite — typically thinner, more uniform, and grey or coloured. The visual difference can be subtle. Slates installed before 1999 should be presumed suspect until tested. Modern fibre-cement slates manufactured after 1999 use cellulose or PVA fibres in place of asbestos.
How do I tell asbestos cement slates from natural slate?
Natural slate is split from rock — irregular thickness, slightly textured cleavage face, mineral colour variation. Asbestos cement slates are pressed from a slurry — uniform thickness, smooth flat face, more consistent colour (often a flatter grey, sometimes painted in colours like red, green or blue). Natural slate is heavier per square metre. Asbestos cement is more brittle. Visual cues alone cannot confirm the material — only a sample can.
Can asbestos slates be reused or re-laid?
No. Reusing or re-laying asbestos cement slates is not appropriate. The drilling, handling and movement involved releases fibres. The only compliant pathway for asbestos cement slates is removal under controlled conditions and disposal as hazardous waste through a permitted waste collector to an authorised facility. Re-roofing means new (non-asbestos) slates, not the old ones.