Inclined roofs basically consist of: roofing material, pitched (also called truss, armor or reticulated) and framing (made up of straps, rafters, slats or nailers).
The upper cladding of the roofs is given the name of roofing material (it should be noted that in the case of a shed constructed of metal structure the entire shell of the ship is called roofing material), and it is the part of the same that plays the real role against the effects of climate and atmosphere.
Today there are many different roofing materials from traditional roofing tiles (ceramic, flat, Greek colonial, Dutch, French), slates, galvanized sheets, to the newest pre-painted sheets, polycarbonate sheets, glass, metal tiles, rigid polyurethane sheets, and systems pre-assembled with injected polyurethane. It could be said that new materials appear continuously with many advantages not only in the thermo-acoustic insulation but also in the ease of installation and speed of assembly.
The choice of the type of roofing material will depend fundamentally on the climatic, economic factors and the type of destination of the construction, on the other hand this choice determines the slope that the roof should have and the type of framing that should be used.
As has already been said, according to the type of roofing material used, it will be defined in the framework on which it rests.
The elements that make up the framework are: belts, rafters and slats.
Straps: these are steel or wood elements that support the plywood by joining them together perpendicularly to each other. In the case of using sheet metal as a roofing material, only belts are used, while in the case of tiles or slates, rafters and slats are also used. The belts must be dimensioned taking into account the action of the following load states:
– Pp + wind
– Pp + s/c
– Pp + operator
Due to the inclination of the roof, the belts are required to bend obliquely.
Rafters: they are arranged perpendicular to the belts and in the direction of the slope of the roof. The states of load acting on them are the same as those considered for belts and must be verified by simple bending. Their separation will depend on the type of cover and the dimensions of the slats.
Slats: These elements receive the covering material directly, have the direction of the belts and generally their squares are 1″ x 2″ or 2″ x 2″, sometimes substituted by the following by boarding in the case of roofs made of tiles or slates, or by removing them completely from corrugated sheet metal roofs.
From the above, it can be seen that the purpose of the framework made up of belts, rafters and slats is to reduce free spans in order to place the roofing material correctly. On the other hand, this decrease in free spans also causes a decrease in the square of the elements used. Not all the elements mentioned are always necessary. Pissed off:
This name (such as trusses or, in the case of older bibliographies, reinforcements) is given to the main resistant structures of the roofs, which support the weight of the framework of the roof. They are reticulated in various ways according to the lights to be covered, the slopes by the roof material and the type of lighting or ventilation needed according to the destination of the construction. They receive loads in their plane and their bars are subjected to tensile or compressive stresses.
The states of load to consider in the cabreadas are:
– Pp + wind
– Pp + s/c
– All those other states of load that according to the place of emplacement are
necessary to analyze as recommended by the CIRSOC (snow, ice, earthquake, etc.).
The greater the number of lights to be covered and the greater the distances between riders, the more complex their configuration will be.
The most elementary truss is simply formed by a brace and two pairs. This structure serves only when the lights are very small (from 4 to 5 meters). For lights between 5 and 6 meters is added a vertical element that joins the ridge with the brace and is called pendolon, resulting in this way a more solid and resistant structure.
For greater loads and lights diagonals (or tornapuntas) are added that will diminish the buckling lights of the pairs.