Modern houses, as a rule, have an attic floor, because this is a great opportunity to get additional living space. Consider how you can build an attic rafter with your own hands.
Mansard roofs are different, they can be one- or two-level, gable, hip or broken. There are a lot of options for creating an attic floor, it all depends on which house project was chosen.
Naturally, the type that the attic truss system has also depends on the project.
Types of rafters that are used to build an attic
During the construction of the attic floor, both layered and hanging rafters can be used. Often, both of these types are present in the roof structure.
Hanging rafters differ from layered rafters in that they are supported only on two bearing surfaces - walls, columns, etc. Such a system works in compression and bending, transferring the resulting horizontal force to the bearing walls.
To reduce the load on the system, a crossbar is used - a beam that connects the rafter legs. When placing the crossbar at the very bottom, it can perform the functions of overlapping.
Layered do-it-yourself roof rafters have additional support in the center. As a rule, this is an internal load-bearing wall or a column located in the center. This system works only for bending, so when using it, it is possible to reduce the load on load-bearing walls.
Materials used to make rafters
During the construction of the attic, the rafters can be made from:
- wood;
- Reinforced concrete;
- Metal.
Sometimes combined options are used - wood with metal.
Wood is perhaps the most popular material for making rafters. Its advantage is that the system can be easily adjusted to the required size. After all, wooden rafters can be cut or built up very easily.
The disadvantages of this option include the instability of the tree to various external influences.Therefore, before use, wooden parts are treated with impregnations that have antiseptic and flame retardant effects.
In addition, when using wooden rafters, it is necessary:
- Carry out waterproofing of places where wood comes into contact with brick or concrete;
- Be sure to provide ventilation products.
Rafters made of metal and reinforced concrete are more durable and resistant to various influences, but they are almost impossible to adjust in size. Therefore, they must be ordered only after all measurements have been taken.
In addition, such truss systems are of considerable weight, therefore, during their installation it is impossible to do without the use of construction equipment.
Mansard roofs from a combination of hanging and layered rafters
Such a device of the attic truss system is quite common.
- The sloped rafters of the lower slope are regular right triangles. To increase the strength of the system, additional tacks are added to the top and bottom of these triangles.
- The top of the roof is formed by hanging rafters, the lower tightening of which can be used to install the ceiling in the attic room.
- The puff does not experience heavy loads, so a beam with a small section can be used to create it.
- So that the puff does not bend under the weight of the ceiling, it is hung on an additional mount - the “headstock”.
- The rafter system itself must be mounted from a material with a large cross section, since this design forms a full-fledged roof and must be durable.
- Installation of rafters in the lower part of the ramp can be done with and without the installation of struts.
- To attach the rafter legs to the Mauerlat or rafter elements, special fasteners are used - sliders or hinged-fixed brackets.
- Racks of the lower rafter legs are supported on the ceiling. . In the event that it is made of reinforced concrete, the installation of an additional element called the bed is provided.
- If the surface of the floors is even, then the bed is laid on the waterproofing. If leveling is required, then use leveling pads.
- In the event that the floors are made of wood, then it will be necessary to insert the racks into the beam, after calculating the load on the racks.
Mansard roof with eaves
If the roof project provides for the installation of a cornice overhang, then the installation of the truss system is carried out without a Mauerlat. Beams are used as a substructure.
If such attic truss systems are being built, then the following rules should be followed:
- Under the lower bevels of the rafters, struts must be installed with fastening to the wooden floor beams.
Advice! The insert should be made to a depth not exceeding a third of the thickness of the beam.
- The lower rafters experience large wind loads (due to the steepness of the slopes) plus the load exerted by the upper slopes, so they are designed for compression.
- Anchor connections for fastening rafters or wire clamps are used as additional fastening.
- You can unload the beams somewhat by installing racks at the intersection of the strut and rafter leg. The lower end of the post must rest on the floor beam.
Mansard roof made of rafters
mansard roof can only be built from layered rafters.
In this case, the lower slopes are mounted in the same way as in the first two cases, but the upper slope has significant differences:
- The upper tightening of the rafters forming the lower roof slope must be made of a material having a large cross section. The fact is that this puff will play the role of a support when creating the layered rafters of the upper slope.
- The lower ends of the rafter legs, forming the lower slope, rest on the floor beams.
- When using a light weight material to cover the roof, additional cross beams can be added, this will help reduce the pitch of the rafters.
- In such a roof, the main supporting function is performed by the frame of the attic room, while the rafters themselves will play “secondary roles”. That is, during installation, the frame of the room is first knocked down, and then runs are placed on the finished support.
Mansard roof in a small house
If an attic is being built in a summer cottage or just a small house, the truss system should be assembled in the following order:
- Inserting racks into beams forming a floor;
- Installation of rafter legs for the formation of lower slopes;
- Installation of a beam for the upper ceiling of the attic;
- Inserting a ridge rack into a beam forming the upper floor of the attic;
- Installation of rafters in the upper slope;
- Installation of additional fasteners in the places where the beams are attached to the ceiling.
Conclusion
From the material presented above, it can be seen that the installation of a truss system (especially in the construction of small houses) for a mansard roof is not particularly difficult.
The main difficulty is the creation of a competent project based on load calculations, in compliance with all the requirements of SNiP.Therefore, it is advisable to entrust this part of the work to professional designers, and the installation work itself can be carried out without using the services of builders.
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