What the slates are made of
Natural slate is split from rock. Asbestos cement slate is a manufactured board of cement reinforced with asbestos fibre and pressed into small tiles. From the ground the two can look much alike, and on an older roof weathering, moss and lichen hide the difference further.
Where the age of the roof is known, the question narrows. The HSE's pre-2000 presumption is about the building, not only the roof, so it also points at soffits, boards and downpipes of the same age.
That is a rule for safety, not proof. A house built before 2000 that was re-roofed in natural slate later has a roof that is not asbestos cement, while one with its original covering still on needs the question asked. Until a test says otherwise, treat the answer as open and keep the roof as it is.
Check the paperwork too. A survey report, a roofing invoice or the original building records may name the material, and any of them is worth digging out before a ladder goes up.
Clues from the ground and the loft
Some signs are worth noting, though none of them settles it:
- Very regular slates of the same colour, thickness and size, with square corners and no flaking edge layers.
- A smooth, slightly matt face and a surface that has weathered to a patchy grey rather than splitting into layers.
- Holes that look machine-drilled and equal along the rows.
- A soffit or fascia board of a similar flat, grey sheet material.
Natural slate varies more. Its edges are rougher, and old slates often split into thin leaves, which is delamination. Our page on man-made and natural slate describes the difference in more detail.
From inside the loft, look at the underside without touching anything. Asbestos cement slates sit on battens like any slate, so the loft rarely tells you more than the age of the timbers.
Stay off the roof. HSE guidance A14 classes asbestos cement roofs as fragile at all times, and a slipped foot can crack the material and release fibres. Do not climb up with a ladder to peer at the surface, and do not scrape or brush a slate to see what lies underneath.
Getting a sample tested
The reliable answer is an analysis of a sample, taken by someone trained to do it so the break is small and the dust is controlled. Ask a roofer or a surveyor who handles asbestos to arrange it, and ask for the laboratory report in writing.
Do not break off a corner yourself. Handling an unidentified slate, bagging it and posting it on is the worst way to find out, because a damaged edge releases fibre where you stand.
Once the type is known, the options open up:
- Not asbestos: it is an ordinary slate roof, and repair or re-roof is a normal job.
- Asbestos cement in sound condition: leaving it undisturbed and having its condition checked is one option, and planned removal is another.
- Asbestos cement that is broken, weathered through or leaking: a plan for removal comes before the next storm.
Keep the written result with the house records, so the next owner or surveyor does not have to guess. A report also lets any roofer price the work on facts, because the method and the waste route depend on what the material is.
Removal, waste and the licence question
HSE puts the careful lifting of asbestos cement sheets and similar roof products among work needing no licence, provided nothing is broken up in the process. Weathering alone does not change that. Substantial damage does: the job then becomes notifiable non-licensed work and the rules tighten.
Insulating board is another matter. External soffits can be made of it, and work on that board is licensable, the exception being a short job. Where a survey finds it, that part goes to a specialist with the right licence.
The waste has its own route. HSE wants asbestos waste double-wrapped and labelled, then kept in a sealed or lockable skip, never an open one. For a householder's own small quantity, Kent County Council's recycling centres take it by booking at every site but Sheerness, double-wrapped, free up to 5 sacks a month. What a roofer strips off is trade waste, and it moves under a consignment note with a registered carrier.
The cost depends on the area, the access and the condition of the material, so a survey comes before any price. See the slate roof survey for how a roof is looked at, or go back to slate roofing.
