An order for tile-effect metal roofing cut to length should be based on measurements of the finished structure. The roof area from the design is a good starting point but does not replace actual dimensions. The most important are the lengths of the slopes, the widths and the diagonals. To these must be added the position of openings and the agreed terminations at the eaves and ridge. Record the length of the eaves and ridge and both side edges. Check the diagonals. If the roof slope is not a rectangle, length and width alone do not describe its shape. On a hipped roof, mark each section separately. Do not assume that symmetrical elements in the design have identical dimensions once built.

Before buying a metal roofing tile, check that the order specifies the exact profile, format, steel core thickness, coating and coverage area, not just a general name and colour. These parameters determine whether the delivery matches the project. Ask for both sheet dimensions and a clear basis for the quantity calculation, because the total area includes overlaps. Also establish who is responsible for measuring and approving the schedule. A well-prepared document helps avoid shortages and costly corrections on site.

Tile-effect metal roofing is a profiled sheet whose shape echoes rows of roof tiles. Stiffness comes from the steel and the geometry of the pressings. Appropriate protective layers guard against corrosion. The sheet alone does not make up the whole roof, however. It needs support, fixings and correctly made connections. The basis is a thin steel core. On it sit protective layers, including metallic protection and coatings that prepare the surface and finish it. The build-up depends on the specific product. The coating on the underside may differ from the decorative outer layer.