You look at the colour of the roof or façade for many years, in different light and from different distances. The RAL code helps to define it, but does not describe the gloss level or the texture of the coating. A good choice requires a sample and a view of the whole building. It is also worth checking how the chosen shade will affect the appearance of the flashings and later repeat orders. The code organises the name of the colour within a given system. It makes it easier to discuss the material and to match components. However, it does not guarantee an identical impression on every surface. Matt steel sheet, glossy paint on a gutter and rough render can look different despite the same designation.

T7 is a good starting point for a conversation about lightweight cladding. The shallow profiling gives a calm surface, but it does not provide unlimited load-bearing capacity. This profile should be considered a specific façade product, with its own cover width and support requirements. Before buying, it is worth establishing whether it is to clad a wall, a gate, or a small structure. In a low trapezoidal profile, much of the sheet looks almost flat. The narrow profiles create delicate lines. This pattern may suit cladding for containers, a garden utility area, or a small façade. The name T7 refers to a family of profiles of low height, not to the material thickness.

T12 is a low profile that does not dominate visually on a small building. It may suit the elevation of a back-of-house area or a light canopy. However, you must choose the right variant and check its performance on supports. The profile designation does not replace a cross-section drawing. Nor does it give a ready answer as to how large a spacing can be left between beams. It is a family of thin sheets with trapezoidal ribs. The designation refers to the nominal profile height, not the metal thickness. For example, a sheet 12 mm high may be made of steel 0.5–0.7 mm thick. The available range depends on the variant and coating.