A zinc roofing can be installed with a roof pitch of minimum 3° up to 90° (façade). The construction can be either insulated or non-insulated. For an insulated structure the cold roof principle should be applied. The insulation is basically used under the timber rafters and boarding. The ceiling construction should be crack sealed.
The roof usually consists of timber boarding with a thickness no less then 22 mm. From the perspective of ventilation the boarding is not tongue-and-grooved. Fibreboard does not absorb moisture and is therefore not appropriate as roof boarding material. Roof substructures of a different material are permissible, provided that they do not contain substances that attack the zinc surface.
As substructure a timber boarding is mainly used, because this material is suitable for the fixing materials and fit the physical building conditions. It is recommended to use planed timber boards no less then 22 mm, width about 100 mm, not tongue-and-grooved, installed horizontally with gaps between the boards of at least 5 mm.
It is not recommended to use plywood panels as a substructure. The material is waterproof glued and therefore has a minimum absorbing capacity, very high vapour diffusion resistance and is less suitable for fixing the clips.
For the processing of concrete and mortar large amounts of water are used. After the building process is finished, a large quantity of water will evaporate before the concrete is completely dry. This process can take years, with the result that the residual water and condensation precipitates onto the zinc surface. Residual water consists partly of alkali coming from the used material. Direct contact between the concrete substructure and the zinc roofing or cladding must be avoided.
As a substructure a non-ventilated, vapor-tight has certain benefits. The structure, benefits and risks in the application of these structures explained in the following chapters.