Methods for splicing timber along the length. Connection of timber along the length

Wood is natural material containing many defects. To obtain a material with certain characteristics, jointed timber is produced today. Wood defects not only spoil the appearance wooden product, but also affect its durability. In this way, two types of building materials are obtained: glued structural timber and profiled timber. Without modern technology It is difficult to obtain material longer than 6 m for the construction of house walls. The connections can withstand all structural loads well. Because wood defects are cut out and individual elements are assembled into a solid structure. To install rafter systems, ceilings, and floors, you need a smooth and durable planed beam.

Planed larch timber is easy to assemble. Exist the following types of this material:

ordinary;
profiled, which has special grooves and ridges;
glued, during production individual lamellas are glued together into a single product.

Coniferous wood is used to produce profiled material. It is dried to 20%, so it is characterized by uniform moisture content, resistance to rotting, cracking, and takes up to a year to shrink. Glued laminated timber is more expensive than profiled timber. It requires virtually no external finishing.

During construction, planed dry timber 100x150 is often joined along the length. This process is called splicing. The joining method is selected according to the place where the material will be used. If serious loads are expected during operation, then tenon splicing is performed.

Extension may also be required for load-bearing walls oh, and on the dividing partitions. Docking also makes it possible to use material economically. When erecting walls, the crowns must be assembled taking into account the dressing (joints in adjacent rows should be located on opposite sides of the wall, by analogy with bricklaying).

If the material will only experience compression, then it is enough to connect the elements overlay (with oblique or straight cuts). To increase resistance to lateral loads, a lock option is used for joining the material. Extension allows for rational use of the building material.

Features of joining profiled timber

For construction wooden house It is not necessary to use expensive laminated veneer lumber. You can choose more cheap option profiled wood. It is planed and does not require mandatory finishing. Profiled timber is characterized by a unique shape, thanks to which each row of the building fits tightly together. Today, several types of profiles are used. The most popular option is “under insulation”, where space is provided for insulating material.

During construction, the material is connected in different ways:

by lenght;
in the corners;
with other materials.

When building up profiled lumber, it is necessary to provide chamfers along which water will drain. More attention should be paid to the places where the joint is created with another material (you need to know specifications). Wood at different conditions environment capable of expanding or contracting.

Dry planed timber must be joined correctly. The type of splicing is selected based on the architectural features of the building. Joining at angles and lengths is carried out by several in various ways. The difference between each connection lies in the shape of the tenon or groove.

In the corners wooden beam docks:

with the remainder (the end protrudes);
without a trace.

For T-shaped joining and extension in length, the following types of joining are used:

castle;
simple.

Knot-free laminated timber is also joined using one of the listed methods.

How to choose the right connection

Splicing is performed during the construction of load-bearing walls, construction interior partitions, arrangement rafter system, floor. The type of joining used should be selected depending on the type of load:

compression, it is important to perform it so that the ends touch in as large areas as possible;
stretching, a lock connection must be performed;
bending, joint is performed at an angle.

At different types the ends of the parts are cut in a certain way. When joining, jute insulation is placed in the lock. For lengthening, various types of connections are used.

When joining wood using the tenon and dowel method, it allows you to create robust construction having the required rigidity. It is necessary to make high quality keys. Interlocking joints are used to join lumber from which load-bearing walls will be built.

Wood floor splicing

Is the most basic solution. The ends of the joined elements are cut at right angles, half the thickness of the wooden part. The parts are connected by folding one end to the other. The tightness of the joint is ensured by insulation (jute tape is laid). In construction, the strength of the connection is imparted by installing wooden dowels. Additionally, the knot can be secured with screws.

Connection to root tenon

This connection option is somewhat more difficult to complete. A tenon is cut from the end of one of the parts (the size of 1/3 of the section), and a corresponding groove is made on the second (reminiscent of a trapezoid). This labor-intensive connection requires special precision (an angle of 45° is maintained). The corners of the log house are joined in a similar way.

Additionally, the connection is strengthened with dowels. If the elements are joined in this way, the beams do not move horizontally.

Connection in an oblique lock

Splicing timber into an oblique lock

It is most suitable if the node will experience bending load. This is a rather complex type of joining, but in terms of strength such a joint exceeds many. At the ends, an oblique tenon with a groove (with bends) is cut out to the appropriate dimensions. The two parts folded together form a lock. The joint is secured with two dowels.

Splicing by application

Is enough complex type docking. The lock is cut out in two pieces of wood. This is how the two links of the log house are connected to each other. The beam is folded at the ends and spliced with a construction bracket. The dowels are installed in the bottom row.

Connecting beams with dowels

It is also an effective way to splice a crown. Grooves are created at the two ends, and after laying, a wooden dowel is driven in. The joining itself can be done in half a tree (dowels must first be made and holes with a smaller diameter must be drilled). The cutting depth should be 2 cm.

If splicing is performed in this way, then it is a very durable method of joining in the construction of buildings. Grooves are cut out in two parts. The ends are folded, a key is installed in the groove ( wooden insert, a wedge, for example from aspen, can be made of metal). Its shape may vary (prismatic, rectangular). It tightly holds the two parts together.

All methods of splicing, both the simplest and the more complex, require fairly precise cuts on the timber, thereby ensuring a strong connection.

Mankind, using wood, has long invented many ways to build from it. Therefore, a modern builder, when choosing, for example, how to join timber along the length, is guided by the size of the house, the quality and grade of the material, its functional significance, etc.

The choice of one method or another largely determines the thermal conductivity properties and how comfortable and cozy it will be in the house.

Advantages of timber houses and the regulatory framework for their construction

Traditionally, wooden houses, that is, houses built from timber, are always popular among private developers. Such buildings have beautiful view, while it is very easy to give each a special personality.

They are also the most environmentally friendly type of housing, and for suburban construction- this is perhaps one of the most optimal options, as they fit organically into the surrounding landscape. In addition, wooden cottages allow you to create a full-fledged architectural ensemble, consisting directly of a house and other economic and household outbuildings.

Attention!
The construction of houses made of timber does not require strict compliance with all standards, as well as GOST 30974-2002 (adopted 03/01/03).
However, structures built in accordance with all the rules are easier to formalize in the future and obtain various permits.
Compliance with standards is also important when certifying products and structures made of timber.

How to choose a method for joining timber during building construction

Choosing how to properly join the timber is necessary for two operations:

for joining or cutting corners;
for increasing in length (this situation arises if some side of the house or all of them have a length of more than 6 meters, the standard size of the timber).

Before you start building a house with your own hands, or even hiring a team experienced builders, you need to familiarize yourself, and in the first case, thoroughly study how to join the timber at the corners.

Docking with the remainder

Docking with the remainder, i.e. with protruding ends, is usually performed in several ways, including:

in oblo, in the version of corner connections it has the following varieties:
in the fat tail;
oval comb;
half a tree;
to the clap;
in a huff.

Joining without residue (no protruding ends)

"in the paw";
“Oblo” type key groove;
T-joints have several variations:
- straight groove;
- key groove - “bowl” or “cup”;
- trapezoidal tenon: rectangular or symmetrical;
Butt connections are made:
- root thorn;
- dowels.

Joint with remainder

Structurally, a house built using this method is more stable compared to a house built “without residue.”

The oblo method and its variations

Very often the “bowl” method is chosen for docking; sometimes it is also called “bowl”- by external similarity, since a round recess is cut out in the upper part, reminiscent of a bowl or oblo - as it was called in ancient times, that is, “round”. The next log is placed across this “bowl”, in which a “bowl” is prepared for the next one.
Half a tree. The oblo or bowl also has its own varieties, the simplest timber joints of which are made “half a tree”. Additionally, for a tighter connection, a longitudinal groove is made in the bowl - it is necessary for installing the beam of the next crown, after installing the longitudinal one.
Another name for this groove is laying. To ensure greater stability of the structure, the top log is made with a rectangular or round section or dowel.
Joint with ridge. If an oval ridge-shaped residue is left at the bottom of the bowl, the structure of the house will become even more stable. In this case, it is important that the shape of the ridge follows the shape of the groove of the upper beam, but you should pay attention that the groove in this case will be at the bottom.
Kurdyuk. One of the most technically complicated ways laying the timber - “in the fat tail”, but if the corresponding instructions are followed, it is even possible to master and complete it yourself. A special protrusion is also added to the ridge in the bowl, strictly across the bowl and along the log, and in the lower part of the next beam across the groove, a notch is made, specifically for the fat tail.
Okhlop and okhryap. There are other ways to cut the corners of a wooden house, but all of them are, to one degree or another, a type of cutting. For example, “in a big way” or in other words “the Siberian bowl” is the same thing, only in reverse. The upper beam with the bowl is placed on the corner, slamming it down.
The “ohryap” method can be considered intermediate and is similar to the okhlop method, only it additionally has recesses about a quarter of the diameter in depth. This method is used for the transition between an angle with and without a remainder.

Methods of docking without residue: “in the paw” and “dovetail”

The connection without any residue is often performed “in the paw”, representing a joint, only without the end part. The simplest option is a paw with a notch, that is, with spikes and sockets at the ends of the beam, for greater stability.

Such a joint has a big drawback - it is very blown out. Therefore, it is recommended to use a “dovetail” connection, in which the spikes fit tightly together, as if wedging the entire structure, giving it reliability and improving thermal conductivity qualities.

A variation of the previous method is the “dovetail”, which is trapezoidal cuts on both parts, taking into account their tight fit. Such a joint is very strong and has sufficient joint rigidity, but does not have good thermal conductivity.

Important: joining timber during construction, especially for connections using dowels or those made using the fat-tailed method, tongue-and-groove, or with a notch, requires vertical gaps that will help compensate for the shrinkage of the structure.

How to make a longitudinal connection

In the process of building a house with dimensions exceeding 6x6 meters, extensions are always required to obtain the length required for a given structure.

The most common methods are to use connections (listed in order of increasing execution method):

half a tree;
longitudinal tenon on dowels;
longitudinal root spine;
oblique lock.

Connections with tenons and dowels

A joint-to-joint timber connection in half a tree is quite simple to make, but it is not sufficiently reliable and does not provide the necessary stability, therefore it requires the use of nails, dowels, and staples for strengthening. The joint itself consists of recesses half the diameter of the beam at the ends of both.

Experienced builders, in extreme cases, use this method for load-bearing external walls, which, even with additional reinforcement, do not have sufficient strength.

The tenon-dowel connection is more durable and can be made in two versions. main feature– connecting grooves at the ends on both parts and a joint is made butt to joint. To ensure the rigidity of the connection, a wooden dowel is inserted into the groove.

This type of connection practically eliminates the mobility of the connected parts in the horizontal direction. The formation of a connection on the main tenon occurs in a similar way, but with a slight difference: in this case, a tenon must be made at one end and a groove at the other.

Lock connections

If the choice is made on an oblique lock, then it is worth involving professionals, as this is very difficult option. The price the master charges for the work is justified by the increased strength and reliability of the building’s structure. The main difficulty of this connection is the exact observance of proportions for all elements of the oblique lock, since this is what affects the quality and efficiency of the connection.

Today, when choosing materials for the construction of private houses, developers are increasingly choosing wood. This choice is due to a number of positive qualities this building material. Wooden house– it’s primarily environmentally friendly clean house. A wooden house can fit into any landscape, giving it a unique personality and a special atmosphere. To this it is worth adding affordable prices for wood and relative simplicity building a wooden house. And if we take into account the saving of time and money during its construction, then the choice of wood as a building material will be completely justified.

A house made of timber is environmentally friendly and fits harmoniously into any natural landscape; to this we should add the availability of the material and the relative ease of construction.

Our ancestors have accumulated vast experience in construction over the centuries. wooden houses. But today, wooden beams are increasingly used instead of traditional logs. And although the technique of connecting the elements of logs and beams has much in common, it is still somewhat different. Therefore, when building a house from timber, you need to know how to join the timber if such a need arises.

Necessity of docking

Marking and calculations of some types of beam corner connections.

Although the houses being built may differ in the type of wood and the way it is processed, the question of how to properly lay the timber and securely fasten it between the crowns will always be relevant. The service life of a built house depends on these two factors. After all, improper installation will lead to the house gradually tilting to one side. And if the connections between the crowns are not tight, the walls will probably freeze in the winter.

The need to join the ends may arise in only two cases: when cutting a corner and when the length of the wall is more than 6 m (the standard length of timber). You can also add a notch to them interior walls in external walls house under construction, but in this case we are talking about only one end.

Since these are three completely different operations and they perform different tasks, the joining of the ends is performed differently in each case, although it has similar elements.
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Types of timber fastening at corners

There are two types of fastening of beams in the corners: a log house “in the paw” and a log house “in the claw”.

The stability of the entire house depends on the reliability of the corners. There are two ways to join the timber at the corners - with the remainder, i.e. with protruding ends, and without residue. The main type of connection with the remainder is a type of joining “in the area”.
The main types of connections without residue: in the paw, with a key groove of the “in the head” type and T-shaped connections - straight or key groove and trapezoidal tenon, rectangular or symmetrical.

The main advantage of a joint without a residue is considered to be material savings. But on the other hand, a house where the ends in the corners are connected to the rest is more stable. In addition, it resists wind and rain better, and will be less likely to be covered in snow in winter. And everything taken together contributes to a more comfortable atmosphere inside the house. Such a joint is easier for a non-professional to make, so if you do not have sufficient experience in building wooden houses, then it is better to choose this method for corner joints.
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Ways to connect corners with remainder

Most often, for joining corners with the remainder, the “into the bowl” type is used. With this method, the beams are connected to each other using key grooves. Such grooves can be made single-line, double-sided or four-sided.

To install a one-line lock, a transverse notch is made at the end at the junction. The width of such a notch must exactly correspond to the cross section of the end. This method of corner connection is mainly used for profiled timber.

To make a double-sided lock, perpendicular cuts are made at the end on both sides of a quarter of its thickness. During assembly, the cuts are joined groove to groove. It is very important that the grooves coincide with each other as accurately as possible. A large discrepancy in size will negatively affect the reliability of the connection as a whole. In addition, additional sealing of cracks will be required.

If you need to join the timber at the corners as securely as possible, use a four-sided lock. With it, cuts are made not from two, but from all four sides of the end. If the grooves are made correctly, the corner will be folded like a construction set. But you need to have very high qualifications to make them as accurate as possible.

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Ways to connect corners without leaving any residue

The simplest corner joint of this type is the butt joint. With this method, no cuts are needed - the beams are joined at their ends. The connections are fixed with metal plates using nails or staples. However, this method cannot guarantee sufficient tightness of the corners of the house even with perfectly straight ends. Therefore, it is practically not used in the construction of residential buildings.

Using special hardwood keys to connect the ends allows you to make such connections much better. Special grooves are made at the end: in one beam it is longitudinal at the very end, in the other it is transverse not far from the end. When connected, these grooves must coincide so that the key can be inserted into them. Without sufficient experience, it is better to stop at a perpendicular-parallel groove. For greater reliability, professionals make such grooves oblique.

Fastening with a main tenon is the most common type of corner assembly using timber. A groove is made at the end of one of the beams, and the end of the other is sawed off, leaving a tenon of the same size. When connecting, the tenon fits into the groove, thus securing the connection. To make it even more reliable, not one, but several grooves and tenons are made at the ends.

The most reliable fastening This type is “dovetail”, when the spike at the end is not rectangular, but trapezoidal. Accordingly, a groove is made in the end of the joined beam to fit this shape.

There are very important point, which should not be forgotten. When using a “tenon-to-groove” type fastening, in order to compensate for future shrinkage of the log house, it is imperative to leave vertical gaps between the groove and the tenon.

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Longitudinal beam connection

Longitudinal connection of the beam: a, c. half a tree; b, d. with an oblique cut. 1. Nagel. 2. Nest.

Because the standard length timber is 6 m, then when building walls longer length there is a need to join the timber along the length. When choosing joining methods, it is necessary to take into account what force and type of deformation the joint will be subjected to in the future. Without taking these factors into account, it is impossible to properly join the timber.

The most common methods of this type of connection are half-tree, longitudinal tenon on a key, longitudinal root tenon, oblique lock.

If a compression force is applied to the joint, use a half-tree joint. To join a beam along its length in this way, a rectangular groove is made on each beam for half its thickness. The length of the groove should be 2 or 3 times the width of the beam.

The grooves are then overlapped. Such a connection is very unstable, so it must be fastened with nails and additionally reinforced with dowels - rods made of hard wood. The main task of the dowels is to eliminate the possibility of displacement of the connected ends. Holes are drilled in the beams with a diameter corresponding to the thickness of the dowels, into which they are then inserted.

If a tearing force is applied to the wall, the timber must be joined along its length using locks. For this, grooves are also made at right angles, but in a different way. Such a groove is 2 times the width of the beam, while from the end the groove is made to 1/4 of its thickness, and then deepens to 1/2. The resulting ledges interlock the ends with each other. For greater reliability, they also need to be additionally reinforced with nails and dowels or use bolts for fastening.

Longitudinal connection of the beam: a, c. direct patch lock; b, d. oblique patch lock.

If the wall of the house experiences a strong bending force, then increased strength will be needed for the connection. Here, for reliable fixation, “oblique locks” are needed. This is the most complex longitudinal connection in execution, but in terms of reliability it is significantly superior to all other types.

The technique is the same as for conventional lock connections, only the cuts are made not straight, but oblique. When using this connection, it is extremely important to accurately observe the proportions of the fastening elements, since the quality of the joints depends on their accuracy. If possible, the place of such a connection is further strengthened with the help of 2 construction staples, stuffing them crosswise.

Despite such a variety of species, there are general rule, which needs to be carried out. To rainwater did not accumulate in the connecting grooves, with outside the walls must be rounded.

Also, regardless of the chosen joining method, it is advisable to treat the joining area with a special compound, a mixture of epoxy wall and sand or sawdust. Joints treated in this way are more airtight, and the resin glues the joined surfaces together, giving them additional strength.

All these types of connections are described in detail in GOST 30974-2002. But this is not a dogma, but just recommendations. In the process of building a house from timber, each developer himself must decide which type of connection is suitable for his house in each specific case.

Good luck to you! Strong walls for your home!

Beam connections in corners and straight walls of a house require strength and tightness. For tightness timber house The humidity of the building material has a huge impact. If you build a house from timber natural humidity, during drying and shrinkage, the log house will experience significant internal stresses, which can lead to its deformation.

By using lumber that has been dried to 20%, you can nip several problems in the bud at once - cracks, cracks, heavy settlement, etc. Ideally, use profiled or laminated timber for the log house chamber drying. The shrinkage of such a log house will be minimal.

The second method to avoid blowing corners is to make these corners with special, complex joint shapes.

The corners must be strong. The frame is subject to forces from possible ground movements, from its own weight and the weight of the roof, roofing and snow, as well as pressure from the force of the wind. The corners must withstand all loads, and in addition, withstand deformations from vibrations linear dimensions due to rain, snow and changes in heat and humidity conditions.

Corner connection with remainder

Very important advantages of this type of cutting:

Blowing from the street is minimal, even in strong winds and frost;
High reliability. Even if not fixed with dowels, the beams, connected in the corners by one of the types of felling with the remainder, do not move even with moderate movements of the foundation soil under the influence of heaving or seismicity. Lower crowns holds the weight of the top and tight connection of the corners.

Main types of cutting with residue

Method of cutting with a one-sided locking groove

This method is equally good for square timber, and for profiled. One side of the beam is sawn to form a groove, perpendicular to the axis timber. The thickness of the groove is equal to half the thickness of the timber, the width and length of the groove are the same. The lock is obtained when this groove accommodates ½ of a beam located perpendicular to it. Such a crown is tightly fixed in relation to the underlying crown in one direction. Additional fixation with dowels gives the corner sufficient strength.

Cutting with double-sided locking groove

This type of cutting is a little more complicated - you will have to select grooves from both the top edge of the beam and the bottom. The grooves in this case have the same width as with the one-sided groove method and a depth equal to ¼ of the thickness. Double-sided cutting of grooves takes twice as long and requires greater precision, but provides an undeniable advantage - rigid fixation of each pair of beams not in one, but in two directions. That is, spatial rigidity is already evident. Now, with any temperature and humidity fluctuations, shifting the beams and crowns relative to each other is practically impossible.

Cutting with a four-sided locking groove

The cutting is very complex, the grooves can be either symmetrical or asymmetrical, and choosing such a complex groove manually is extremely labor-intensive. Typically, such complex grooves with ideal geometry are made on equipment that produces house kits. Then, at a construction site, these kits are assembled from numbered beams, like Lego constructors.

Complex and expensive processing, but no practical improvement in the tightness of the corner is observed, although in theory such a corner should become absolutely ideal.

Main types of cutting without residue

The angle without any residue saves on lumber. The beam is entirely in the plane of the wall, the ends do not protrude outward. But there is no overall saving, since these angles require additional insulation and caulking. In terms of strength, reliability and protection from blowing, these types of cuttings are also inferior to corners cut with the remainder. Competition can only come from warm corner, aka the root thorn.

Cutting without residue allows you to make the façade of the house more geometrically strict, making it easier to complete exterior finishing. The issue of aesthetics is controversial, and has more to do with style.

Corners from both square and profiled timber are cut without residue.

Butt cutting without residue

The simplest and quick way for the construction of outbuildings. No additional processing is required, simply lay the bars of the required lengths in a checkerboard pattern. To ensure that the beams in the crowns and the crowns themselves do not move relative to each other, with this method of felling it is necessary to use fasteners - galvanized steel overlay plates, steel brackets or wooden dowels.

Labor costs in this case are minimal; carpentry experience may be completely absent. If you make a log house in this way from dried timber, you can get an acceptable result. From raw lumber, as carpenters say, no matter how hard you try, the corner will move after drying. The corner is deformed, and humidity fluctuations will contribute to linear fluctuations, resulting in blown gaps.

Butt cutting with dowels

The key may be different shapes. For a straight key, you will need to select straight grooves along the ends and side surfaces of adjacent beams. Under the dovetail key, you need to choose a rather complex groove, with widening from the middle. The key also has a complex shape.

The connection with a straight key will prevent the crown beams from moving in the horizontal plane, but not in the vertical. Vertically, the crowns will be held only by their own weight and the weight of the overlying structures. Key in shape swallowtail will securely fix the angle and prevent the bars from moving in both directions. This method of cutting without residue gives an almost windproof corner.

Half-tree felling

Also an easy cut. At the ends of the beams, cuts are made to ½ thickness, resulting in a tenon that is the same in length and width. Without fixation with dowels, this connection will not be reliable. After the log house shrinks and settles, the corner will most likely be blown out and will require additional insulation. The second caulking of log houses after curing and settling is always done.

As with butt cutting, you can modify this method by securing the corners with dowels. In this case, the bars will not move.

You can also improve the method of cutting half a tree if you join the ends into a paw. The paw has a more complex shape - the cuts are made inclined, wedge-shaped, exactly to size. The result is an increase in the strength of the log house, the beams are fixed relative to each other in the crowns, and the weight of the overlying crowns prevents the displacement of the underlying ones. The corner looks aesthetically pleasing from the inside and outside, the façade of the house is geometric and smooth.

Connection to a warm corner (to a root tenon)

It is considered the warmest, windproof connection and at the same time guarantees the fixation of the crowns. The method is not the most difficult:

The ends are cut off, leaving tenons, the length and width of which should be exactly 1/3 of the section of the beam. A simpler tenon has the shape of a rectangle, while a more complex tenon has a one-sided widening. The grooves of the joined beams are selected according to the size of these tenons, but without an exact fit, since the grooves need to be caulked with moss, flax or jute fiber, hemp or felt. Bars with spikes are placed on top of bars with grooves. Fastening the crowns with dowels this method felling is a must.

Fastening beams with dowels

The classic wood for dowels is birch, free of defects, knots and cross-layers, and with a parallel arrangement of fibers relative to the longitudinal axis.
The optimal length of the dowels is 0.8 of the sum of the heights of the two connected crowns. Sometimes not two, but three beams are connected with one dowel. The diameters of the dowels are from 25 to 35 mm.
Dowels are installed at intervals of up to 1.5 m, and always on both sides of each corner. Along horizontal rows, the dowels are shifted in a checkerboard pattern.

Connections of beams along the length

Long straight sections of walls can exceed the length of the lumber. The joining of timber along the length is done in one plane. The requirements for connections are the same as for corners - strength and tightness.

The easiest way to join a beam along its length is to join with rectangular dowels. The crowns will be securely fixed in the transverse direction; such a joint will not be blown through. The key is cut slightly smaller than the groove to leave gaps for the caulking. The grooves under the key are sealed with moss, jute and flax fiber and other materials.

More difficult and more efficient way joining beams with a root tenon. Direct splicing is technologically a little simpler than corner splicing, but also requires precision. There should be a few mm gaps between the groove and the tenon to be filled with caulk.

The most complex, costly in terms of material and labor, and at the same time the best in terms of results, type of straight splicing is joining with an oblique lock. The dimensions must be accurate, the fit close to ideal. The lock configuration is not simple. As a result, two beams have two completely overlapped sections in connection, which gives the joint strength, and the clever shape of the oblique lock makes it impossible for a gap to appear even with significant shrinkage.

Often during the construction of roof frames of complex configurations, there is a need to use elements custom size. Typical examples include hip and half-hip structures, the diagonal ribs of which are significantly longer than ordinary rafter legs.

Similar situations arise when constructing systems with valleys. To ensure that the created connections do not cause weakening of structures, you need to know how rafters are spliced along the length and how their strength is ensured.

Splicing the rafter legs allows you to unify the lumber purchased for constructing the roof. Knowledge of the intricacies of the process makes it possible to almost completely construct a rafter frame from a bar or board of the same section. The design of the system from materials of the same size has a beneficial effect on the total cost.

In addition, boards and bars of increased length, as a rule, are produced with a cross-section larger than that of the material standard sizes. Along with the cross-section, the cost also increases. Such a safety factor when installing hip and valley ribs is most often not needed. But if the rafter splicing is carried out correctly, the elements of the system are provided with sufficient rigidity and reliability at the lowest cost.

Without knowledge technological nuances It is quite difficult to make truly bending-rigid lumber joints. The connecting nodes of the rafters belong to the category of plastic hinges, which have only one degree of freedom - the ability to rotate in the connecting node when a vertical and compressive load along the length is applied.

In order to ensure uniform stiffness when bending force is applied along the entire length of the element, the mating of the two parts rafter leg located in places with the lowest bending moment. In diagrams demonstrating the magnitude of the bending moment, they are clearly visible. These are the points of intersection of the curve with the longitudinal axis of the rafters, at which the bending moment approaches zero values.

Let us take into account that when constructing a rafter frame, it is necessary to ensure equal resistance to bending along the entire length of the element, and not equal opportunities to bend. Therefore, the interface points are located next to the supports.

Both the intermediate post installed in the span and the Mauerlat or truss truss itself are used as support. Ridge run can also be assessed as a possible support, but the joining areas of the rafter legs are better located lower along the slope, i.e. where minimal load is placed on the system.

Options for splicing rafters

Except precise definition where to connect the two parts of the system element, you need to know how the rafters are extended correctly. The method of forming the connection depends on the lumber chosen for construction:

Bars or log. They are built up with an oblique cut formed in the joint area. To strengthen and to prevent rotation, the edges of both parts of the rafters, cut at an angle, are fastened with a bolt.
Boards sewn together in pairs. They are spliced with the arrangement of joining lines staggered. The connection of two overlapping parts is made with nails.
Single board. The priority is splicing with a frontal stop - by joining the trimmed parts of the rafter leg with the application of one or a pair of wooden or metal overlays. Less commonly, due to the insufficient thickness of the material, an oblique cut with fastening with metal clamps or traditional nailing is used.

Let us consider these methods in detail in order to understand in depth the process of increasing the length of the rafters.

Option 1: Oblique cut method

The method involves the formation of two inclined notches or cuts arranged on the side where the parts of the rafter leg meet. The planes of the notches to be joined must be perfectly aligned without the slightest gap, regardless of their size. The possibility of deformation must be excluded in the connection area.

It is prohibited to fill cracks and leaks with wood wedges, plywood or metal plates. It will not be possible to adjust and correct flaws. It is better to accurately measure and draw cutting lines in advance, according to the following standards:

The depth is determined by the formula 0.15 × h, where h denotes the height of the beam. This is the size of the area perpendicular to the longitudinal axis of the beam.
The interval within which the sloping areas cutting, is determined by the formula 2 × h.

The location for the joining area is found according to the current rules for all types rafter frames formula 0.15 × L, in which the value L reflects the size of the span covered by the rafters. The distance is measured from the center of the support.

Parts made of timber when making an oblique cut are additionally secured with a bolt passing through the center of the connection. The hole for its installation is drilled in advance; its Ø is equal to the Ø of the fastener rod. To prevent the wood from being crushed at the mounting location, wide metal washers are placed under the nuts.

If a board is connected using an oblique cut, then additional fixation is made using clamps or nails.

Option 2: Placing the boards together

When using bonding technology, the center of the connected area is located directly above the support. The joining lines of the trimmed boards are located on both sides of the center of the support at a calculated distance of 0.21 × L, where L denotes the length of the overlapped span. Fixation is carried out with nails installed in a checkerboard pattern.

Backlash and gaps are also unacceptable, but they are easier to avoid by carefully trimming the board. This method is much simpler to implement than the previous method, but in order not to waste hardware and not weaken the wood with unnecessary holes, you should accurately calculate the number of fastener points to be installed.

Nails with a stem cross-section up to 6 mm are installed without preliminary drilling of the corresponding holes. It is necessary to drill for fasteners larger than the specified size so as not to split the board along the fibers when connecting. The exception is hardware with a cross-section, which, regardless of size, wooden parts you can just score.

To ensure sufficient strength in the bonding zone, the following conditions must be met:

Fasteners are placed every 50 cm along both edges of the boards being joined.
Along the end connections, nails are placed in increments of 15 × d, where d is the diameter of the nail.
Smooth round, screw and threaded nails are suitable for holding the board together at the joint. However, threaded and screw options are a priority, because their pull-out strength is much higher.

Note that connecting rafters by welding is acceptable if an element is constructed from two sewn boards. As a result, both joints are covered with a solid section of lumber. The advantages of this method include the size of the overlapped span, which is impressive for private construction. In a similar way, you can extend the rafter legs if the distance from the top to the bottom support reaches 6.5 m.

Option 3: Frontal rest

The method of frontal extension of rafters consists in the end joining of the connected parts of the rafter leg with fixation of the section with nails, dowels or bolts through linings installed on both side planes.

To avoid play and deformation of the extended rafter leg, you must adhere to the following rules:

The edges of the boards to be joined must be perfectly trimmed. Gaps of any size along the connection line must be eliminated.
The length of the pads is determined by the formula l = 3 × h, i.e. they must be no less than three times the width of the board. Usually the length is calculated and selected based on the number of nails; the formula is given to determine the minimum length.
The overlays are made of material whose thickness is at least 1/3 of the same size as the main board.

Nails are driven into the linings in two parallel rows with a staggered “dispersion” of fastening points. To avoid damaging the overlay, which is thin in relation to the main lumber, the number of attachment points is calculated based on the resistance of the nails to the lateral force acting on the legs of the hardware.

When the junction of the rafter parts is located directly above the support, there is no need to calculate nailing to fix the linings. True, in this case the docked leg will begin to work as two separate beams both for deflection and compression, i.e. according to the normal scheme you will have to calculate bearing capacity for each of the constituent parts.

If steel rod bolts or rods without threads, dowels are used as fasteners when joining thick boards or timber, then the threat of deformation will be completely eliminated. In fact, even some gaps in the joining of the ends can be ignored, although it is still better to avoid such flaws.

When using screws or screws, pre-drill holes for their installation; the Ø of the holes is 2-3 mm less than the same size of the fastener leg.

When making frontal connections of rafters, it is necessary to strictly observe the design installation pitch, the number and diameter of fasteners. When the distances between fixation points are reduced, wood splitting may occur. If the holes for the fasteners are larger than the required dimensions, the rafters will be deformed, and if they are smaller, the lumber will split during the installation of the fasteners.

Extension with composite rafters

To connect and increase the length of the rafters there is still quite interesting way: extension using two boards. They are sewn to the side planes of the extended single element. Between the extended parts there remains a gap equal to the width of the top board.

The gap is filled with scraps of equal thickness, installed at intervals of no more than 7 × h, where h is the thickness of the board being extended. The length of spacer bars inserted into the lumen is at least 2 × h.

Extension using two extension boards is suitable for the following situations:

The construction of a layered system along two side girders, which serve as a support for the location of the joining area of the main board with the attached elements.
Installation of a diagonal rafter that defines the inclined edge of hip and half-hip structures.
Construction broken roofs. The strapping of the lower tier of rafters is used as a support for the connection.

Calculation of fasteners, fixation of spacer bars and connection of boards is carried out by analogy with the methods described above. For the manufacture of spacer bars, trimmings from the main lumber are suitable. As a result of installing these liners, the strength of the prefabricated rafter significantly increases. Despite the significant savings in material, it works like a solid beam.

Video about ways to build rafters

Demonstration of basic splicing techniques structural elements rafter system:

A video with a step-by-step description of the process of connecting rafter parts:

Video example of one of the methods of joining lumber:

Compliance with the technological requirements according to which the rafters are spliced along the length guarantees trouble-free operation of the structure. Extension methods can reduce roof construction costs. You should not forget about preliminary calculations and preparation for making connections so that the result of your efforts becomes ideal.