A roof truss is a frame that supports the entire roof covering. He is also responsible for the shape of the roof. Rafters are an important element of a truss. Roof beams are very important and choosing them correctly will ensure the safety of your roof. For this reason, it is useful to know what the standard rafter sizes should be.
Rafters are the main element that forms the roof truss in single-family houses. First of all, these are load-bearing beams, the task of which is to transfer the weight of the roofing to the structures located below. Considering the classic structure of a truss, it is built from rafters, beams, walls, transom beams, columns, swords, purlins and dampers. There are three types of farms:
- rafter beam
- with collar beam,
- with a running belt.
Rafter dimensions for the truss
- Usually the thickness of the rafters is min. 5 cm. Otherwise, the structure will be unstable and the truss will not be rigid.
- The cross-section of the rafters is usually 7x14 or 8x16 cm.
- The dimensions of the rafters are usually twice the height in relation to the width. For this reason, the cross-section of the timber for a gable roof has dimensions, for example, 5x10 cm, 7x14 cm or 9x18 cm.
- However, the designer at this stage may decide that it is necessary to use the maximum length of the rafters, but the cross-section should reach, for example, 5x12 or 8x20.
- The maximum distance at this location is 1.20 meters.
Rafters at the farm
- Considering the roof truss, this is the simplest type of roof truss, used on a 6-meter wide roof with a 45-degree slope. The maximum length of rafters cannot exceed 5 meters. The rafter distance in this case is a maximum of 80 to 120 cm.
- The collar beam truss, in turn, is usually used in houses with an attic and a gable roof, where its width is from 6 to 9 meters, and the maximum length of the rafters is 12 meters.
- The standard length of the rafters here is more than 4.5 meters.
Farm selection
The correct choice of truss and its size depend on the size of the building and its shape. The purpose of the attic in the building and issues related to financial, architectural and aesthetic value are also important here. Each time the decision must be made by an authorized and competent designer.
- In this case, inclined beams of rectangular cross-section are appropriate as rafters. They perform the function of rigidity of the roof truss structure.
- In addition, the rafters must support the roof covering resting on them. For this reason, roof beams must be resistant to external factors and can withstand the expected loads. The safety and stability of the roof depends on the beams.
- Depending on the truss used, the rafters are supported by purlins. Sometimes this can also be a ridge, wall sheathing, collar beams or intermediate purlins.
