The roof is a complex, multi-component structure, the design, assembly and installation of which represents a serious obstacle for an inexperienced craftsman. The most important stage roofing construction is considered a device rafter frame, which sets the shape, slope and load-bearing capacity of the slope. The rafters bear the load from the weight roofing material and snow, so they must be strong and durable. But what to do if the length of the slope is much greater than the standard size of lumber? In this article we will tell you how to correctly splice rafters together to increase the length of this element.
Rafter legs or rafters are the main elements of the roof truss frame, which are arranged in pairs along the ridge connection, forming inclined planes of the slopes. They are usually made from healthy, durable wood or metal profile. In the roof structure, rafters perform the following functions:
- The shapes and angle of inclination of the slopes are formed. It is the angle between the rafters and the base of the roof that sets the recognizable geometry of the roof, making it easier for melt and rain water and snow to drain off the surface of the slope.
- Distributes weight evenly roofing. Roofing pie taking into account snow load can weigh up to 300 kg/m2, therefore the rafters must withstand significant weight along the entire length, and also distribute it between load-bearing walls.
- They serve as the basis for fixing the roofing material. Finish coating They are attached to the sheathing, nailed across the rafters of the frame.
Note! There are three rafter parameters that are determined when calculating and creating a roof project: the length of the rafter leg, the distance between them and the cross-sectional size of these elements. They mainly depend on the slope of the slopes, climatic conditions and the weight of the finishing coating.
Materials
Rafter legs that distribute weight waterproofing coating and thermal insulation of the roof between the load-bearing walls on which the slopes rest must have high load-bearing capacity and excellent strength properties. In addition, they must be light so that, despite their considerable length, they do not bend under their own weight. Optimal materials for the manufacture of rafters consider:
- Tree. Wood is a lightweight, durable building material that can be easily processed by hand with the most primitive tools. Rafter legs made from this timber with a cross-section of 100x100 mm or 150x150 mm can withstand up to 500 kg/m2. Due to the fact that the standard size of lumber does not exceed 6 m, the tree is used for the manufacture of private rafters, because when the length of the slope exceeds 6 meters, it is necessary to build up the boards. Disadvantage wooden rafters They are considered to have poor resistance to rotting, so they are treated with antiseptic compounds.
- Metal. Metal rafters are used mainly in industrial construction, since household, commercial and industrial buildings, as a rule, are large in size. High load bearing capacity metal profile allows the use of elements of a smaller cross-section. In addition, the metal has high stability corrosion.
Experienced craftsmen note that even if the length of the slope exceeds 6 meters, the rafters for the roof frame can be made of wood. Moreover, it is absolutely not necessary to purchase expensive lumber of non-standard length. At large size roofs splice the rafters or add fillets to them.
Extension methods
The length of the rafter leg is the sum of the length of the slope and the length of the roof overhang, so it can exceed the standard lumber size of 6 meters. To lengthen the boards from which the rafters are made, you need to connect two or three boards together. To typesetting rafter leg has not lost its strength properties, it is necessary to correctly calculate the splice location and securely fix it using one of the following methods.
When laying a log bathhouse or house, the main technological operation is correct styling logs In order to carry out all the work correctly, you need to know how to connect timber, of which there are several, and the final result depends on this.
During the work, a connection will be required in two cases:
- When length standard timber insufficient and you will need to increase it.
- For tying corner joints.
For each case, there are several connection options, which we will consider below.
There are two main methods of corner connection: with and without a remainder. If the joints are processed without residue, the corners of the log house will be smooth, but in the second case, the ends of the beam will protrude for some distance. This accordingly affects material consumption and is considered a minus. But this method there is also positive side: the corners will be better protected from rain precisely due to this design, and besides, a log house folded in this way is much more stable.
How to properly connect to the remainder
The timber can be connected to the remainder in three ways:
- in "ohryap";
- in "oblo";
- in the "clap".
The simplest second option is in the “oblo”, or as experts also say, in a cup. In this way, the timber is connected in three ways:
- one-sided;
- bilateral;
- four-sided.
One way connection
The first option is done as follows. A perpendicular groove (bowl) is cut out in each beam at the joints. It needs to be made so that it matches the size of the log laid on top. Many people use this method construction companies because in terms of time and technological costs this is the simplest option.
Two-way connection
This is a more complex option, and the quality of the work depends on the professionalism of the carpenters. Here the groove lock is cut from the top and bottom of the logs.
The main thing is to take into account the diameter of the beam, while the depth of each bowl should be no more than ¼ of the height.
Four-sided lock
With this design, the grooves are sawn through on all four sides. If you correctly calculate the diameter of the timber and accurately cut the grooves, the logs will fit like a construction set, which will allow you to achieve maximum strength of the log house.
Corner connection in "oblo"
This connection method also has three options:
- in the fat tail;
- oval comb;
- half a tree.
Here the simplest and most common method is the third - half a tree. The technology of operation is in some ways similar to the connection in the “oblo”, only in addition to the cut-out bowl, an additional longitudinal groove is cut into the laid block (it is also called a laying groove). Before laying the next log, it is filled with insulation, and only after that they begin to process the next beam.
The technique for sawing out a bowl to form a fat tail is presented in the video below:
To make the fastening more reliable, each log is connected using dowels. These are like this wooden dowels round section, they allow you to ensure reliable stability of vertical logs.
In the second option (oval ridge), when cutting out the laying bowl, a small oval ridge is left in it, which must coincide with the longitudinal oval groove of the next beam and, accordingly, a reliable connection is made through this ridge.
The third option (tail tail) is considered the most difficult in terms of technical execution. When arranging such a connection, when cutting out a bowl, a special protrusion is left at its bottom, which must be positioned exactly across and coincide with the longitudinal groove of the next beam. This ledge serves as a connection to the next log.
The “clasp” connection also deserves due attention. Here, fastening is also done by cutting out a bowl, but only it is cut down from below the stacked log.
Laying logs in an “ohryap” is a technologically complex option. With this method of joining, bowls are cut on both logs. In addition, in both bowls they are cut down longitudinal grooves, which serve as a reliable fastening.
Joining timber without residue
The basis of this connection is the technology of laying in the “ohryap”. Only when cutting down the bowl, the end part of the logs is completely removed, depriving the corners of the protruding part. To increase the reliability of fastening, special nests with spikes (prisek) are left at the end of the logs being connected.
If you cut out an ordinary connecting paw with a “cut,” it will be blown by the wind, as a result of which the log house will need to be additionally processed.
To avoid this, horizontal cuttings are made with a slight slope in two directions. This method is called “swallow’s nest”.
Due to the spikes in inclined plane better clamping of the structure is ensured, which helps to increase thermal insulation.
If you use fat tails, dowels or dowels for fastening, be sure to provide a vertical gap between the tongue-and-groove connection. This is necessary in case of shrinkage of the log house.
In the video below you can see how grooves are cut to connect the timber in the corners and along the length:
Longitudinal connection options
The standard length of lumber, and in our case it is timber, is 6 meters. But sometimes you need to lay a longer frame, and here you will need to make a longitudinal connection.
The following options are used for this:
- half a tree;
- longitudinal tenon;
- longitudinal root
Longitudinal fastening using tenon and key technology is considered the most reliable. To make a connection, an internal groove is cut out on one log, then a butt joint is cut according to its dimensions on the other log, which should fit tightly into the groove. For reliability, it is also connected with a key or bracket.
A dowel is a kind of fastening that is made of iron or wood, but only hardwood. The shape of the keys is prismatic and rectangular.
This method is similar to corner mount timber in “half a tree”. The ends of the logs that need to be joined are cut to half their thickness and butt-joined to each other. For strength, they are connected with a dowel or an iron bracket.
This is, of course, the simplest option, but in terms of reliability it is ineffective. Specialists rarely use it in their work.
Longitudinal root
In this fastening option, a groove is cut out on one log, and a fastening tenon is cut on the other. For reliability, it is better to make a tenon trapezoidal shape(dovetail). This will eliminate vibrations of the logs in the crown.
We invite you to watch a video about how a groove is cut in a beam with a longitudinal connection:
It is better to entrust the work of laying logs to professionals, but if you decide to do it yourself, then maximum attention and effort will be required from you, and you can tell our readers about the result of the work done.
High-quality connection of beams to each other during the construction of a house is of no small importance. The reliability of the entire structure and the preservation of heat in the house largely depend on the method and accuracy of the connection.
From quality connection timber depends on the strength and thermal insulation characteristics future design.
Construction wooden houses With new technologies for manufacturing timber, it has become rapidly gaining popularity. Ecologically pure material with good thermal conductivity and attractive appearance, ideal for construction residential buildings and other buildings in any region of our country.
The most important stage in the construction of wooden houses is the jointing of the beams with each other. Highly specialized equipment for making tenons and grooves is used only in large industries, in view high cost and large sizes. However, connections of profiled timber can be made with your own hands.
Necessary tool for making connections
Figure 1. Types of timber connections.
At self-production connections, you can use conventional hand-powered tools available from the developer or specialists, such as:
- Chainsaw with petrol or electric drive. Can be used manually circular saw with an electric drive, but the maximum permissible cutting depth of the device must be more than half a tree.
- Set of chisels. IN trading enterprises It is not always possible to find a tool of the required length and strength, so it is advisable to make it yourself or order it from a blacksmith.
- Hammer, mallet, axe.
In the old days, cutting corners was done with a single axe, but it was time-consuming. Modern instrument With various types drive will significantly facilitate work and reduce time spent on work.
Basic methods of connecting timber during installation
At the connection point, you need to choose a specific method that guarantees optimal strength and tightness of the joint. Corner connections can be made:
- with ends protruding beyond the main dimensions;
- without protrusions;
- butt laying, when the beams do not overlap each other;
- T-shaped connection for walls inside the building.
Figure 2. Construction of a rectangular root tenon.
The technology of the method with a remainder provides best quality corner connection, but requires higher flow material. Each beam produces from 0.4 to 0.6 meters of wasted length. With a height of 15 crowns, the total unused length will be from 20 to 36 m. With a beam length of 4 m, this will amount to from 5 to 9 additional products. You can see the corner connection with protruding parts in Fig. 1a.
The first crown in a building is usually placed in a joint with a key groove with a specific name for the joint - “oblo”. This method is used for any method of laying material, with or without protrusions. The sampling is performed at half the thickness of the product. The articulation of the corners of the house without protrusions can be seen in Fig. 1b. To prevent displacement in the main planes, subsequent crowns must be joined using the “root tenons” type with the installation of dowels. The design of a rectangular main tenon is shown in Fig. 2.
Nagel represents wooden block round section 25 cm long and about 30 mm thick. In the beam laid on the cushioning material, you need to drill a hole with a depth exceeding the length of the dowel by 20-40 mm, and hammer the part into it.
Butt jointing of corners is the most in a simple way. The quality of such joints is extremely low; creating a warm corner in this way is unrealistic. The timber is fastened with such joining using metal brackets with spikes, nailed down. Laying timber end-to-end is shown in Fig. 1st century How to fasten a beam with a metal bracket can be seen in Fig. 1e.
Figure 3. Dovetail.
T-shaped connection of capital and internal partitions has several options:
- joint using a key groove;
- “groove-tenon” joint in the form of a symmetrical trapezoid;
- “groove-tenon” joint in the form of an asymmetrical trapezoid with a right angle;
- use of a rectangular mortise-tenon joint.
Spikes in the form of trapezoids are designed to maintain the connection during loosening of the structure and efforts aimed at pulling apart in different directions. The design of such joints is complex, but also more reliable. Because of appearance the connection was called the “dovetail”. The structure of such a joint can be seen in Fig. 3. Manufacturing " swallowtail» requires care and patience when adjusting surfaces.
The connection can be assembled and disassembled only by moving the products in a vertical plane.
Many craftsmen prefer to fasten walls using rectangular tenons. T-joints are often fastened with special brackets, long bolts and washers. large diameter or nails. An example of a right-angle tenon connection is shown in Fig. 1 year
Longitudinal material connection
Figure 4. Butt and overlay joint.
One of the main disadvantages of timber is its length limitation. Standard sizes manufactured products range from 4 to 6 m. For long walls or when using scraps, it is necessary to make a longitudinal connection. Such connections are undesirable in the construction of capital walls due to possible deformation. If it is necessary to install longitudinal joints in several rims, they cannot be placed in adjacent rims along the same vertical line. For interior walls There are no restrictions on merging timber due to a more stable temperature regime.
When splicing timber along the length, use a central tenon or various joints with a lock. The most commonly used lock is a straight lock due to simple process manufacturing. Samplings are made in the timber to the extent of half the thickness of the timber. The resulting surfaces are available for processing and can be carefully adjusted.
A beam connection that is reliable against displacement can be obtained by using a central tenon. The nest must be made slightly longer than the length of the spike. The length of the tenon should be twice the width of the beam. To connect more firmly, you can install two spikes.
Extension of the beam can also be done with an overlay. The overlay connection can be oblique or straight. Types of connections can be seen in Fig. 4. The ends of the products must be given the selected shape and placed in place. Subsequent crowns will compress and secure the connection with their weight. When lengthening the beam in main walls it is advisable to use a combination various fastenings. Products fitted to the overlay connection must be additionally secured with one or two wedges. A view of a wall with spliced timber can be seen in Fig. 1d. All connections must be sealed with sealing material.
Making corner joints of timber at an indirect angle
Building designs always contain corner connections timber whose size does not correspond to 90°. On most buildings, such corners are located in the attic part of the room. Their size depends on the slope of the roof. On main walls, angles of various sizes can arise when installing protruding or recessed elements.
It is advisable to make joints at an obtuse or acute angle using the “groove-tenon” principle. Protrusions and recesses are cut out under required angle, their surfaces are adjusted accordingly. To increase strength, you can use additional fastening with bolts, screws or nails of the required length. If the thickness of the products is large, you need to use metal brackets of the required shape with appropriate fastening.
During production large quantity identical joints, it is advisable to make special marking templates that will speed up and facilitate the process of applying markings for connecting logs in a log house.
For templates you can use tin, plywood, thick cardboard, thin plastic. When making joints, you should first make a cut in the desired position, then remove areas inaccessible to the saw with a chisel.
Ready-made building designs offered by manufacturers building materials, equipped with profiled timber with connections. All types of tenons and grooves are selected based on the required strength and are manufactured on industrial equipment with high precision.
Over many centuries of using wood in housing construction, vast experience has been accumulated in working with lumber. But today the material is largely different from what it was before. Products can differ not only in the type of wood, but also in its grade and processing method.
Methods for connecting timber in length
The standard length of the beam is 6 m. In the construction of walls exceeding this figure, it is required to build it up, which is done using the ligation method, which eliminates the location of the joints on the same line. To do this, the connections in the rows of beams are made alternately: first the missing section will be laid on one side of the house, then on the other.
The crowns are built up using the “key groove” method, otherwise it is called “half-tree”. This is the simplest way to connect a beam and is done by deepening one end into the thickness of the second. To do this, the corresponding sides of these elements are cut down to ½ thickness. For greater confidence, the joints are fixed using pins or other fasteners.
The double-sided lock is more complex. It is a joining of lumber using the “groove to groove” method. To do this, make at the ends of the connected beams perpendicular planes cut cut. Each of the fastened elements must have its own groove and its own tenon, but they must be positioned so that when the ends are connected, the protrusion of one fits into the recess of the other, and vice versa. In this method of lengthening, it is very important to maintain the dimensions of the cuts, otherwise the strength of the joint will be questionable.
Another way to join lumber is “blind frying pan”. It is more often used in corner joints, but is also good for extending lengthwise. To fasten lumber using this method, a tenon in the form of a triangle with a horizontally truncated apex is cut out at one end of the beam, and a groove of a similar shape is cut at the second. Docking is done by placing a tenon on top and driving it into the groove.
What is the most effective way to lengthen timber?
The most reliable connection is considered to be a four-sided groove. But it is very difficult to make cuts, so it is rarely used in practice. This requires maximum accuracy in calculations, measurements, and cutting. Therefore, such work is trusted only to professionals. Previously, craftsmen could make these complex cuts with a single axe. Today, developers are armed with modern, powerful tools, but not everyone is able to make this complex “lock”: skill in such work is still necessary.
If you decide to build wooden house made of timber, then you will undoubtedly need the help of specialists, or at least first become familiar with such a concept as connecting timber along a length. How well you know about the construction wooden house its further maintenance also depends, or in extreme cases, this knowledge will be useful when dismantling the building. Often you have to deal not only with wood processing but also with connecting structural parts.
Typically, the standard length of rough, profiled or glued beams is 6 meters, so when constructing a log house of a wooden house that is longer than the standard, it is necessary to use technologies for connecting along the length.
The timber is joined along its length in cases where one side of the house is longer. The bars are joined on one side with a bandage, and the next row on the other side. This order eliminates the incorrect location of two joints located one under one. Profiled beams are usually connected in several ways in accordance with GOST 30974-2002, the name of which is: “connections of corner wooden paving and log low-rise structures. Classification, designs, sizes." Typically, this standard applies to T-shaped connections, as well as corner connections of low-rise buildings that are built from logs or timber. These standards are not mandatory, but there is one thing, but these requirements must be taken into account when certifying products, such as profiled timber or entire production.
The type of splice used depends on the load on the beam - loads can be compression, tension and bending.
For the method of connecting timber along the length (splicing), you must also use Various types connections, such as:
- Half-tree connection
- Connection with key
- Connection with main tenon
- Connection with oblique lock
- Connection with rim lock
When connecting timber under compression force, it is necessary to use the notches shown in the figure above. The length of the fastening is equal to the width of the beam + 10 cm. Also, when building a house from timber, the connection must be reinforced with dowels.
The drawing shows locks for connections under the influence of tensile forces, which resist longitudinal displacement. They also need to be reinforced with dowels.
Depending on the type of connection, the ends of the timber being connected are cut in a certain way. At the moment of connection, insulating inter-crown jute is placed in the lock.
You can read more about the connections of beams and logs here
Video standard half-tree connection: