A single crack does not necessarily mean the whole roof slope must be replaced. However, several similar defects may point to a problem that goes beyond a single sheet. Corrugated fibre cement sheets should be assessed together with their fixings and the supporting structure. Asbestos-free fibre cement makes local repair worth considering, provided compatible components are available and the cause of the fault is known. The decision should be based on an inspection and on the cost of a durable solution, not solely on the number of visible cracks. In an old building, the name used by the owner does not always confirm the composition of the covering. It is also possible that only some sheets were replaced. If asbestos is suspected, do not begin by drilling, cutting or removing a fragment on a trial basis.

An agricultural building can become a workshop, a warehouse with different conditions or a commercial space. The roof then no longer performs exactly the same function. Corrugated fibre cement sheets can remain part of the solution, but they must be assessed together with the structure and the new layers. Asbestos-free fibre cement does not on its own provide the comfort of a heated interior. Adaptation is best begun with the requirements of the future use, rather than with the idea of quickly covering the old ceiling. The statement that 'the building will be used commercially' is too general. It is necessary to establish whether it will be heated continuously, how many people will be inside and what work is planned. Sources of moisture, heat, noise and pollutants are important.

An old corrugated roof may conceal more than one type of material. Individual sheets were replaced during successive renovations, and the names used by owners are often colloquial. New corrugated fibre cement sheets are not the same as old asbestos cement products. The term asbestos-free eternit describes a modern material, but it does not allow the composition of the existing roof slope to be assessed. Before planning replacement, information must be gathered without unnecessarily damaging the covering. The word "eternit" is sometimes applied to various corrugated sheets, regardless of their composition. The information that the roof was bought as asbestos-free may be valuable, but it is worth finding confirmation. Invoices, renovation descriptions, delivery notes and old photographs will be useful.

Replacing the sheets does not mean that the entire roof structure always has to be replaced. Nor does it justify leaving it without inspection. Corrugated fibre cement sheets require a structure suited to the weight, loads and method of fixing. Asbestos-free fibre cement can be considered for a renovated building only after assessing the existing roof. The key question is whether the old elements and connections will safely perform their function in the new arrangement. It is worth checking whether the roof was raised, extended or repaired after damage. Past alterations may not be visible on the original design. Periods of leakage, dampness and major internal alterations should be noted. Removing a wall or adding equipment may affect the structure.