What is a fibre cement slate?
A fibre cement slate is a thin, flat sheet of cement reinforced with fibres, used as roofing or wall cladding. In Dutch it is called a vezelcementlei. It is a man-made alternative to natural slate: the slates are lighter, dimensionally stable and cheaper, but have a more uniform appearance and generally do not last as long as good natural slate.
Composition and asbestos
These slates used to be made of asbestos cement. Since the asbestos ban in the Netherlands (1993) they have been made asbestos-free, with cellulose and plastic fibres as reinforcement. The following therefore applies:
- Slates from before 1994 may contain asbestos. Do not drill, saw or sand them, and do not remove them yourself without knowing what they are. If in doubt, have an asbestos survey carried out by a certified company.
- Asbestos-free slates often have a manufacturer’s code on the back. If you are in doubt, have a sample tested.
Installation
Fibre cement slates come in rectangular and diamond-shaped formats. Like natural slates, they are laid on roof boarding or on battens and each slate is fixed with nails or with copper or stainless steel hooks. Important:
- Keep to the manufacturer’s minimum roof pitch and headlap. These differ per format and laying method; if the pitch is too shallow or the lap too small, rain will blow underneath.
- Use stainless steel or copper fixings. Galvanized nails rust over time and leave rust stains.
- Cutting and drilling: use tools with dust extraction or work wet, because asbestos-free fibre cement also gives off dust containing quartz. Wear a dust mask (at least P2, preferably P3).
- Provide ventilation behind the slates when used as wall cladding, so that moisture can dry out.
Recognising it
Fibre cement slate is uniform in thickness and colour and has crisp, straight edges. Natural slate is layered, varies slightly in thickness and often has an irregular dressed edge.
| Fibre cement slate | Uniform in thickness and colour, with crisp, straight edges |
|---|---|
| Natural slate | Layered, varies slightly in thickness, often with an irregular dressed edge |
Related terms
- Slate roof
- Roofing slate
- Natural slate
- Asbestos
- Wall cladding
- Roof boarding
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.