The choice of covering depends above all on how the garage is used, not on its floor area alone. Check whether the garage is to be heated or used only for parking, and whether you store tools or bicycles there. Moisture brought in by a wet car calls for thought about ventilation and limiting condensation. Examine the roof pitch, support spacing and loads, and with planned heating also the insulation of the entire enclosure. Only then compare trapezoidal sheet, modular metal tile and sandwich panel.

Thin metal sheet coverings are among the lightest roofing options, but compare the mass of the whole system rather than the sheet alone. Check whether the data in the product sheet refer to a square metre of total area, effective coverage or a single sheet, as these are different units. Convert both coverings to kilograms per square metre of effective coverage and add ridges, flashings and accessories separately. Remember that profiling changes stiffness and the amount of material per roof area, and the load table must match the ordered variant. Leave the final selection decision to the designer.

A complete roof comprises the structure, protective layers, covering, flashings and drainage, plus insulation and airtight junctions with partitions in a heated building. When pricing, check whether the offer covers all these elements together with installation and transport, rather than comparing the material price alone. Differences in delivery scope and parameters may not be visible at first glance, so ask for an itemised breakdown of works and materials. This helps avoid a seemingly cheap order and allows cost control.