An anti-condensation layer on the underside of the sheet can reduce dripping of water formed by condensing vapour. It acts as a temporary store of moisture that must subsequently dry out. It is most often considered in adequately ventilated buildings with an uninsulated covering. It does not replace thermal insulation, a vapour barrier or repair of a leaking roof. Whether it makes sense to buy depends on the conditions inside the building and the possibility of removing moisture. The roof surface can cool to a temperature at which the vapour contained in the air begins to condense. Droplets then appear from below, even though no rain has passed through the covering. The phenomenon depends on surface temperature and air humidity. It may be noticeable after a cool night or with a large difference in conditions between the interior and the surroundings.

Structural trapezoidal steel sheet is selected to carry loads in a specific arrangement. It can form the load-bearing substrate of a roof or an element of a floor solution. Its height is often considerably greater than in a typical covering sheet. However, the profile number alone does not determine the choice. Calculations, the appropriate tables and the definition of supports and connections are required. Use on a floor requires particularly precise definition of the sheet's function. A covering sheet also transfers local loads, such as snow and wind, to its supports. In structural sheet, load-bearing capacity is a fundamental part of its role in the arrangement. A high section depth allows other stiffness and span parameters to be achieved.

The spacing of battens under trapezoidal sheeting is determined by the load capacity of the specific sheet and the roof loads, not by one universal module. It is therefore worth checking whether the chosen profile and its documentation match the support scheme, roof pitch and site conditions. Also consider the condition of the structure, the evenness of the supports and the layer arrangement. T18 and T35 require separate selection of thickness and fixings, and the designation alone is not enough. Below we discuss the choices facing the building owner and the contractor, and the trade-offs to consider before installation.