Steel roof base

Steel roofing, made of galvanized or black roofing steel sheets, is laid along the lathing made of 50×50 mm bars. Bars are placed every 250 … 270 mm (Fig. 1).

Fig. 1. Steel sheet roofing:
a – general view; b – types of folds; in – supra-cornice crutch; 1 – rafter leg; 2 – Mauerlat; 3 – supra-cornice crutch; 4 – lathing; 5 – standing seam; 6 – recumbent fold.

Along the cornice, ridge, gutters and roof edges, the sheathing is made by continuous covering with boards of 50×20 mm. Boards can be edged or unedged. Roofing steel sheets are attached to the lathing with clamps made of sheet steel strips. Both bars and boards are pre-antiseptic. The lathing is attached to the wooden rafters with bolts and nails. The rafters and the sparse lathing have the same slope – 16 … 24 °. Steel roofing battens are made of pine, spruce, fir and aspen. The moisture content of the wood used for the manufacture of the lathing is 12%.

Molded materials (bars and boards), supplied with a moisture content of up to 25%, are stored in stacks with dense stacking, and with a moisture content of more than 25% – in stacks that provide natural drying of materials; a dense roof is arranged over the stack. Parts for roofs are stored in closed rooms, laid on gaskets to protect them from bending, breakage and ground moisture. To protect the wood of the roof sheathing from decay and extend its service life, the wood is impregnated with antiseptics, coated or painted. The service life of wood is increased if it is dry covered with linseed oil. To significantly increase the service life of dry wood, it is coated with resin.

In order to increase its rot resistance, the wood of the sheathing should be treated with water-soluble antiseptics, since the sheathing is not expected to be moistened during operation. The most widely used water-soluble antiseptics include sodium fluoride and fluorosilicate, copper sulfate, sodium dinitrophenolate. Sodium fluoride NaF is a white powder, slightly soluble in water, odorless, does not destroy wood and iron, which is very important for steel roofing. Sodium fluoride is used for impregnation and coating of wood in the form of a 3% solution at a temperature of 15 ° C. Sodium fluoride cannot be used in a mixture with lime, chalk, gypsum. Sodium fluorosilicate Na2SiF6 is a powder that is poorly soluble in water; its antiseptic properties are close to sodium fluoride. Apply it in the form of a hot solution mixed with sodium fluoride in a ratio of 1: 3.

Due to its easy flammability, the wood of the sheathing must be protected from ignition by processing with fire retardant chemicals – fire retardants, which either melt at high temperatures or release gases that prevent combustion. Evenly impregnated dry wood does not ignite at high temperatures, but only smolders. Impregnation of wood with fire retardants is performed in the same way as impregnation with water-soluble antiseptics, which gives better results than coating with fire retardant paints.