Plechová střecha 4,8 mm

From the seam spacing to the right size

A polystyrene sheet whose longer side measures thirty centimeters and the shorter one half of that, with the pattern of a metal roof. The lengthwise standing seams, which on a real building arise where two metal panels are joined, are 4.8 mm apart here.

The seam spacing on this type of roofing is a surprisingly constant quantity. Metal panels are made in widths which, once the joint is worked in, give a covering module of roughly four hundred to six hundred millimeters, and that holds from barns to station halls. You can calculate backward from it: four hundred divided by four point eight works out at 1:83, six hundred at 1:125. This sheet therefore hits the band of railroad sizes, where there are also the most buildings to be built.

Anyone who uses it on a figure scene will get a different result. A factor of thirty-five gives a module of one hundred and sixty-eight millimeters, that is, metal joined every sixteen centimeters, which you will not see on a real roof. The surface then reads not as standing-seam roofing but as a finely ribbed sheet, and the viewer subconsciously takes it for a smaller structure.

The pattern is shallow and easily flooded, so apply the paint thinly. Rust is well done with pigment rubbed in along the grooves, because water on a real roof runs down exactly there.

Do not build the roof from a single piece but from strips laid from the bottom up with a small overlap, exactly as real roofing is laid. Each further strip covers the top edge of the previous one and a shadow arises that the sheet on its own cannot offer. At the eaves let a few millimeters overhang the wall and pack the strip from below so that it keeps its slope. The ridge is finished from a strip bent over a ruler.