Roof - from the structure to the covering

Roof
The roof refers to the load-bearing structure of the roof, whose purpose is to support the roof covering and simultaneously transfer the loads generated by snow, wind, and its own weight to the load-bearing walls of the building. In modern architecture, we can encounter not only wooden roofs but also steel or reinforced concrete ones. However, for conventional use, typical family and residential houses most often use wooden roofs. The function of transferring weight is fulfilled by the entire system of battens but primarily by posts and purlins, which transfer the weight to the outer walls of the building and subsequently to the foundations. Currently, high-quality spruce wood is most often used to produce this material, which, after processing, is mostly chemically treated (impregnated) to prevent rot, pest infestation, or decay after a certain period.

Roof Structure
The design of the roof depends primarily on the size of the building, span, slope, and shape of the roof, the purpose of the building, and the overall environment in which the object is located. In the Czech environment, the most widespread truss system is found. In this system, the main elements are the ties and purlins. Under the term "ties" lies the transverse profile of the roof, which essentially supports its other parts. A purlin is a horizontal beam running longitudinally across the roof and supporting the rafters, while rafters are sloped elements of the roof, carrying the roofing battens on which the roof covering is attached. Furthermore, there are elements referred to in builder circles as braces, struts, posts, or hangers. Each has its specific application, without which the roof would not fulfill its function. All joints are carpenter-made, currently done with machinery, precisely crafted to fit together accurately. In addition, the joints are securely bolted together with screws, which in the case of historical buildings are replaced with wooden dowels.

Roof Layer Composition
The roof of the building must be appropriately insulated to provide the users of the building with adequate protection and comfort. According to the ventilation method and the placement of vent spaces, we distinguish sloped roofs into single-layer, double-layer, and triple-layer. Single-layer roofs are now used minimally, meaning a roof without insulation, without a foil, with tiles loosely laid on battens (e.g. barns). The decision about the specific type depends on the designer and investor, on the construction possibilities, on local conditions, and primarily on the way the building will be used in the future. The thickness of thermal insulation and waterproofing is influenced by the beam construction of the roof, more precisely the size and spacing of the beams. This implies that there is no single method for insulating roof trusses. What does exist, however, are standards for thermal protection of buildings that should be respected and adhered to. Insulation is usually laid in two layers, namely between the rafters and under the rafters. However, we may also encounter above-rafter insulation. To prevent water or moisture, which can penetrate under the roof covering during extreme weather conditions, from getting further into the building, a separate waterproof foil is placed under the covering. Above this safety waterproofing, a vent space is left, which must have an inlet at the eaves and an outlet at the ridge. This way, moisture is discharged, allowing for air exchange. The vent space is considered a crucial structural detail that influences the lifespan of the entire roof structure. Ventilation is managed in the roof covering with vent tiles and at the ridges with ventilation strips.

Roof Covering
On the counter battens, which are nailed to the rafters, battens (usually sized 4x6 cm) are nailed, which support the roof tiles. These constitute the topmost part of the roof structure and the entire object, and are thus exposed to all climatic influences. The highest quality covering has been clay tiles for many millennia. During their production, many innovations have occurred, and today sliding tiles, tiles with engobe or glaze, tiles of various shapes, designs, sizes, and colors are available.