How to fix the rafters to the frame - installation and
A wooden blockhouse made of logs or timber is a traditional building for the territory of Russia, which can be used as a residential house or a bathhouse. The process of assembling such a dwelling takes place according to the technologies verified by centuries, therefore it turns out to be warm, cozy and comfortable for life. Special attention should be paid to such a technological operation as the establishment of a truss frame, on the strength of which the protective qualities of the roof depend. In this article we will describe how to properly fasten the rafters to the framework, so that they can withstand the weight of even the heaviest roofing material, but not deformed during the shrinkage of wood.
Functions and views
The truss system is called the frame of the roof, the set of supporting elements, which together give it shape, slope and significant bearing capacity. The backbone of the roof is made from dry, durable wood, treated with antiseptic preparations, or a metal profile. It serves as the basis for fixing the roofing, as well as evenly distributes the load between the bearing walls. To block the log house, use the rafters of the following types:
- Hanging. Hanging rafters have only one point of support - on the mauerlat, with the free end of the legs they rest against each other, forming a three-hinged triangular arch. This design is used if the frame inside does not provide for bearing walls on which racks can be installed. Hanging truss system is experiencing stress on bursting, so it includes all sorts of tightening to compensate for this voltage. Rafters of this type are characterized by massiveness and complexity of installation.
- Outcast. Suspended rafters have two points of support - the mauerlat and ridge girder, which is supported by vertical posts. Such a construction can be used only if the inside of the log house has at least 1 supporting wall or a number of columns to which the ridge can be unloaded. The suspended rafter system is under pressure only on the deflection, therefore it is easier to mount it.
Note! The frame is made of natural building material - wood with unique properties. After assembling the structure, the humidity of the wood begins to level off, so it shrinks during the first 3-5 years of operation. The most significant size changes occur in the first year of service; therefore, it is recommended to mount the rafters only after this time.
Mounting methods
Fastening rafters to a wooden frame is a technologically complex process, the correctness of which depends on the strength, integrity and durability of the roof. In the work it is necessary to take into account that the tree in the process of drying settles, therefore the geometry of the structure changes. In addition, this material is subjected to thermal expansion, therefore, too rigid attachment of rafters on the frame causes deformation. There are two types of truss mounts:
- Moving Mobile fixtures rafters called special "slide", made of metal. Thanks to them, the trusses do not experience stress on the deflection, and also react to the slightest temperature fluctuations, adjusting the geometry of the log. Sliders allow you to fix the truss system until the house shrinks without the risk of deformation.
- Stationary. Fixed mounts do not provide a small amount of mobility when fixing truss legs, however, they guarantee rigidity and strength of the structure. As fasteners used nails, screws, wooden dowel, metal brackets and lining.
Important! A wooden blockhouse has a unique ability to “breathe”, it regulates the humidity in the room itself, therefore it does not have rigidly fixed dimensions. Movable fasteners that respond to shrinkage of the walls and thermal expansion of the material are the best option for fixing rafters to the framework.
Assembly methods
After complete shrinkage of the wooden frame, the craftsmen proceed to the adjustment of the truss frame and the construction of the roof. This process is painstaking and difficult, especially if you perform that task alone. There are 2 ways to install the frame on the mauerlat:
- Installation of finished roof trusses. This technology consists in assembling roof trusses “on the ground” and further lifting them to the installation site as a finished product. Raising massive and heavy structures requires special equipment (aerial platform, crane or tractor). In this way, mounted slings that weigh less are installed.
- Building farms "on top". If the construction of the truss system has a large weight and size, and there are no special equipment at the builders disposal, then the trusses are assembled right on the spot. The disadvantage of this technology is considered the complexity and inconvenience of work.
Keep in mind that experienced craftsmen rarely use the technology to install ready-made truss trusses, as it does not allow for precise fitting of elements, although it significantly saves time.
Sequence of work
The main factors of the quality of the truss frame are the accuracy of the calculation of the ridge height and the length of the rafters and the detailed adherence to the production technology of works on the construction of the roof. In order for the roof to protect the log house well from the penetration of precipitation, it is necessary to mount the rafter legs as follows:
- First you need to take a flat board of coniferous wood without cracks or knots. To increase the service life of truss feet, they are treated with an antiseptic and fire retardant. To reduce the consumption of impregnation, it is better to touch the wood.
- Then make the template truss legs, which serves as a model for the production of the remaining rafters.
- First, install the first and last truss pair, and then stretch the cord between them to align the remaining rafters.
- They fix the remaining truss pairs, trim the ends of the legs so that they are even, and then install the crate.
Experienced craftsmen recommend to monitor the correctness of attachment of rafter legs with the help of a building level, so that the roof is flat, without distortions.
