Load types for the
structure The load is divided into two types: permanent and temporary.
Constant load is divided into such impacts:
- Strength from the weight of the structure
- Force from the weight of the roof
- Strength from the weight of the roof and the roofing threshold
- Strength from the ceiling weight of the attic, if it is
Temporary load means:
- Possible Precipitation( snow, rain)
- Weight of people walking on the roof during maintenance and operation
- Wind force
- Strength of water currents that may be in summer
How to calculate
Calculation of the distance between rafters is also done taking into account the materialand the diameter of the rafters. Calculations are made at the construction stage of the building by architectural organizations. For installation, it is recommended to use special legal and reference documents, which indicate the features of the phased arrangement of all the legs of rafters, crate material and other quantities.
For buildings of houses, it is very rare to project the distance of the rafters in projects, because they mostly lay their hopes on the experience of the builder. It is extremely rare, but it happens that the site owners are asked to calculate the number of rafters for the construction of the roof.
Therefore, it is important to first determine the type of roof and attic( its heating, the characteristics of residential or non-residential condition), as this affects the number of rafters and the system as a whole.
Important! Documents for the implementation of calculations: SNiP 2.02.96 and "Revisions in SNIP 3.03.97", in which everything is written in the o with the climatic map of the Russian Fed e radio.
Recommended material for the truss system:
- Trees coniferous, having a moisture content of 15-25%
- Another board, timber, etc.without blossoming and other signs of an unhealthy structure
Handle the wood carefully, so apply flame retardants and antiseptic to protect the products from rotting, as well as a possible fire. The type of material and its cross-section, the length of each rafters also determine the calculation.
Estimated approximate deductions
The average ruler of the rafter pitch is 0.6 - 1.0 meters. What factors affect it you already know, so tell the basic actions of the calculations:
- Determining the number of lengths of the roof. It should be divided into the distance between the rafters, which you determined yourself
- Then the number must be rounded up to the big side. It expresses the number of rafters for the whole side of the roof
- The number showing the length of the side of the roof is divided by the number of legs and the figure is calculated equal to the progon between the rafters' lines, the same step of the rafters that you calculated earlier.
- The length of the step may vary depending on the roofing material andThis is the angle of the roof slope.
The example is as follows: the length of the track is 17 m and the distance between the fasteners is 0.7 m
17 / 0.7 + 1 = 25.2 = 26 meters. This number means the required number of rafters for the construction of the ramp.
Important! For a steep roof with a large angle of inclination, the rafter should be made as large as possible. The reason for this is the incomplete distribution of the load on the roof and the supply of most of the load to the walls.
Look in the adjacent tab of the video, in which the author describes in detail the device of the rafter system. This will help you complete your calculations.
