The sheet format affects the appearance of the roof slope, the number of joints and how installation is organised. Fibre cement sheets are best compared in relation to a specific building form. Asbestos-free fibre cement in shorter sheets can produce a finer division, while a large format can emphasise the continuity of the roof. Neither of these effects exempts you from structural requirements. On a small gazebo a large sheet may occupy a considerable part of the visible roof slope. On a vast hall the same format will be just one of many repetitive elements. It is worth assessing how often horizontal laps are to appear. Their rhythm influences the perception of the roof's proportions. There is, however, no rule that a small building always needs a small sheet.

A corrugated roof has a clear rhythm that is visible even from a distance. Corrugated fibre cement sheets allow this rhythm to be used in simple, orderly architecture. Asbestos-free fibre cement does not have to be associated only with utility buildings. The effect is determined by the proportions of the building volume, the division of the sheets and the way the edges are finished. The repeating profile lays bands of light and shadow across the surface. When viewed from the side, these can be more pronounced than when seen straight on. The height and pitch of the corrugation matter. It is not worth choosing a profile solely from a small colour sample, because across a large roof area its rhythm becomes an important part of the building. In a simple volume, such a material can be the main means of expression.