When changing a roofing material for one that is lighter or heavier, we always recommend consulting a structural engineer to give you appropriate advice on load bearing. It is true that on some refurbishment projects, fibre cement slates may be unsuitable to replace an existing natural slate roof. However, at around 44kg/m², our Edgemere concrete slates are not that different in weight to a natural slate, so they could be a suitable replacement but it would depend on the structure of the building and planning conditions.
Interlocking slates are designed to be very quick and easy to install, with a high coverage rate – ours is 9.7 tiles per square metre. Like all interlocking tiles, they should be fixed to BS 5534 recommendations, both for new build and refurbishment projects.