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 also has 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 work is in some ways similar to the connection in the “oblo”, only in addition to the cut-out bowl, an additional longitudinal groove(it is also called styling). 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 wooden dowels with a round cross-section; they help 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, longitudinal grooves are cut out in both bowls, 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 the corner fastening of timber into a “half-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 the spike in a 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.
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.
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 depends 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. Besides, 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 extension in length (this situation arises if some side of the house or all of them are more than 6 meters long, standard size timber).
Before you start building a house with your own hands, or even by hiring a team of experienced builders, you need to familiarize yourself, and in the first case, thoroughly study how to join beams 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 option corner connections 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. Oblo or bowl also have their own varieties, the most simple joints timber from 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 dowel 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 corners wooden house, but all of them are, to one degree or another, a type of region. For example, “in a big way” or in other words “the Siberian bowl” is the same thing, only in reverse. Top beam with the bowl he presses himself onto the corner, slamming it.
- 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 junction has big drawback- it is blowing very hard. 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 a 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 joining.
Connecting timber into half a tree or in another way during the construction process requires a responsible attitude. Can be used perfectly for wood different types fastenings, the durability of which is due to the high strength of the material used. Wooden buildings They are distinguished by environmental friendliness, increased strength, and attractive appearance.
One of the most important stages The construction of houses made of wood is the construction of a log house. Correct joining of the timber allows you to reliably lay wood material, connecting the workpieces to each other. Lifetime wooden log house depends on the reliability of installation of products. This affects the sound insulation characteristics and ability wooden walls retain heat.
Types of beam connections
The choice of beam splicing method is influenced by the features of the structure and the type of material used. In this case, they can be used different types timber connections. Violation of technology during the construction of a log house often leads to disastrous results.
Before making a connection with your own hands, you need to think about how to properly join the timber. If this is done incorrectly, then cracks will begin to appear in the building, and the building itself will begin to tilt. Finding a way out of this situation is not difficult, since you can connect the timber in several ways:
- Butt.
- On dowels.
- Half a tree.
- Dovetail.
- On the root spines.
It is necessary to know all the basic techniques used in the construction of wooden structures. Not all methods are overhead; they differ significantly from each other, which is why these technologies require a special approach.
Corner connection method
Modern construction of wooden structures involves the use of two types of corner joints:
- Without a trace (“in the tooth”, “in the paw”).
- With the remainder (“into the bowl”, “into the cloud”).
The connection of the timber in the corners with the remainder suggests that the ends of the frame finished construction will protrude beyond the boundaries of the wall by about 0.5 m. This construction method is more expensive, but it has a number of advantages:
- heat transfer decreases;
- the reliability of the structure increases.
Corner joints of timber
The use of the method of connecting with the remainder “into the bowl” involves sawing out the key grooves. Methods for connecting timber in the corners with the remainder are as follows:
- Unilateral.
- Bilateral.
- Quadruple.
This type of connection involves creating a notch, that is, a perpendicular groove on the upper side of the beam. The corner connection of this type of beam does not require significant effort and large quantity time.
The creation of a four-way locking groove, which requires great skill and experience of carpenters, provides a fairly strong fastening. A groove is cut out on each side of the product. The crowns are stacked like a construction set. This technique ensures greater strength of the log house.
Butt joint technique
Joining beams using the butt method involves creating a connecting seam by attaching one beam to another at the ends. Each element is overlapped on top by the next product. To create a reliable connection, the ends of the products should be sawed off at an angle of 90°.
Even if the butt joint is tight enough, this does not guarantee the absence of heat loss, which will be too large. This is unprofitable, especially when building a bathhouse from timber. The “butt” connection method can be replaced by a more reliable “root tenon” method, which is also called a “warm corner”.
Butt joint of timber
The joined timber is secured with studded steel plates. They can be hammered in with staples or nails. In order for the surface of the product to be perfectly flat, the carpenter must be able to adjust the ends of the joined beams. Due to the low tightness of the corner, periodic loads may occur.
Experienced builders do not recommend using the “butt” method, which is considered one of the fastest methods. Otherwise, heat loss will be very large. This will not save time and effort for complex species connections. The “butt” method of joining timber without residue is not suitable for all types of buildings.
Connection using the "dowel" method
Laying timber spliced using dowels allows you to obtain a reliable and durable wooden structure. To join timber at the corners, wedges are required, that is, dowels (dowels) made of hardwood. Ideal to use for timber wood dowel, for example, from aspen. The key, which fits into the cut groove, connects the products very tightly.
Connecting timber with a key
Wedges make it possible to achieve high strength of the log house and reduce its thermal conductivity. The elements are attached to dowels driven into the joint, which is pre-cut. The key may have different shape: prismatic, rectangular, dovetail, straight or serrated.
When splicing beams that work in tension, notches are used to protect them from longitudinal displacement. This type of splice is called a lock. In some cases, the notches have to be strengthened with bolts or dowels; in this way they can be connected.
Products connected using keys must have grooves that are identical to the grooves of other elements. Dowels are wedges that connect two wooden element, dowels are transverse, longitudinal and oblique. Application last type keys are available only to professionals.
Assembling a log house using the half-tree method
An improved method of assembling half a tree involves the use of a dowel. This allows you to increase the strength of the corner joint. Connecting timber along its length is also possible by laying it in half a tree. The entire structure is strengthened using dowels.
The element connected into half a tree is sawn halfway across. Hence the name of the structure itself, since the size of the cutting is equal to half the section. Holes for dowels are pre-drilled in the product. Dowels should be inserted near corner joints. The length of the dowel is calculated so that it is enough for several products at once.
Connecting timber using the half-tree method
The corner connection is created by cutting at the top and bottom. This is how 2 links are processed. To ensure the greatest strength of the connection, wooden bushings are used, which are mounted at the ends of the cutting. The option of oblique cutting is also acceptable for creating a reliable log house using the half-tree method.
This type of corner fastening is widely used in construction residential buildings. For example, in the process of constructing log houses from profiled timber. All joints are carefully insulated. To reduce the ventilation of the structure, cutting is done with a slight slope, and not at a right angle.
Method of joining into a “root tenon”
Method corner assembly The "root tenon" is the simplest type of castle connection. The method is used to obtain reliable fastening from spliced elements. The root tenon is a structure that includes a tenon and a groove rectangular shape. Their dimensions in height and width are 4 cm with a beam cross-section of 150 mm. It is quite easy to cut out a tenon and groove according to the diagram.
Method of connecting timber with a root tenon
The "root thorn" method is the most common. In one of the joined products, a special groove is made at the end. The end of the other is connected to the first beam using a vertical tenon. All work should only be carried out by an experienced carpenter.
Each subsequent crown is laid using wooden dowel, which has round section. When laying elements in a “root tenon”, it is necessary to use flax-jute fabric to increase the density of the assembly and improve the thermal insulation of the log house.
If the logs are one-dimensional, then the marking can be simplified by making appropriate templates. It is possible to carry out more thorough compaction of the cuttings. To do this, you can use the “paw with a root spike” assembly method.
Dovetail connection
The structure of the assembly structure using the dovetail method resembles a “root tenon”. The fastening method is used for corner connections, T-shaped and in length. When cutting out a tenon and a groove at the end of the product, it is necessary to maintain identity. The sealed connection is ensured by the trapezoidal shape of the tenon.
Method of connecting dovetail beams
The T-shaped assembly design is widely used in the construction of houses made of timber. There is no need to leave additional overlaps on the internal surfaces of the walls of the building. The dovetail technique allows the use of smaller cross-section elements.
Insulation of corner elements during installation is carried out using jute fiber. However, the system is not permeable. Before laying using the dovetail method corner mounts can be cut down in a way that is similar to the “half-tree” technique. The cutting should have trapezoidal shape. Each product is stacked one on top of the other. Variety horizontal mounting corners using the “dovetail” method is the connection of the timber “into the paw”. The product is sawn horizontally, which involves the creation of trapezoidal recesses, suitable friend to friend.
Fastening via longitudinal connection
To increase the insufficient length of the timber, carpenters recommend using the appropriate technique. It is not difficult to choose a method of longitudinal connection, since the following methods allow joining timber:
- Half a tree.
- Tenon with key.
- Root thorn.
The ends of each product must be sawn through, making grooves for joining the beams. Reliability of the assembly is ensured through the use of tenons with keys. Joining timber along the length is high-quality and reliable, it is carried out by analogy with in an angular way, allowing the timber to be spliced.
Methods for longitudinal connection of timber
Lengthening a beam using the longitudinal root tenon method involves cutting out a groove at the end of one product and a tenon at the other end. The greatest fastening strength is achieved by giving the tongue and groove trapezoidal shapes.
Any of the presented and outlined methods of constructing wooden buildings has its own characteristics. But there is general tips, which are suitable when using any assembly technique. The beam must be rounded with outside to prevent rain or melt water from stagnating in the grooves. The contact points between the elements must be perfectly aligned and polished. Additional density of the structure can be ensured by coating the joint with a mixture of resin and sand.
Watch the video on the topic of our article.
The rafter system is the most complex and one of the most important elements of the house; the comfort and operating time of the building largely depend on the correctness of its construction. Calculation and design rafter system should only be done experienced builders or engineers with special training.
Designing a wooden rafter system is much more difficult than any metal constructions. Why? In nature, there are no two boards with absolutely identical strength indicators; this parameter is influenced by many factors.
The metal has the same properties, which depend only on the grade of steel. The calculations will be accurate, the error will be minimal. With wood everything is much more complicated. In order to minimize the risk of system destruction, it is necessary to provide a large safety margin. Most decisions are made directly by the builders on site after assessing the condition of the lumber and taking into account the design features. Practical experience is very important.
Why do you need to splice rafters?
There are several reasons why rafters need to be spliced.
- Roof length exceeds standard lumber length. The standard length of the boards does not exceed six meters. If the slope is large, the boards will have to be lengthened.
- During construction there is a lot left good boards 3–4 m long. To reduce the estimated cost of the building and reduce the amount of unproductive waste, these pieces can be used to make rafters, having previously spliced them together.
Important. It must be remembered that the strength of spliced rafters is always lower than that of whole rafters. You should try to ensure that the splice point is located as close as possible to the vertical stops.
Splicing methods
There are several ways to splice, there is definitely no better or worse. Craftsmen make decisions taking into account their skills and the specific location of the joint.
Table. Methods of splicing rafters.
| Splicing method | Brief description of the technology |
|---|---|
| It is used on boards with a thickness of at least 35 mm. Quite a complex method, it requires practical experience execution carpentry work. In terms of strength, the connection is the weakest of all existing ones. The advantage is saving lumber. In practice, it is used very rarely on construction sites. |
| The length of the rafter legs is increased with the help of an overlay. The cover can be wooden or metal. If the length of two sections of boards is not sufficient according to the parameters of the rafter system, then this method allows you to increase them. Butt joints have the highest bending strength and are widely used during the construction of various structures. |
| Overlapping. Two boards are fixed with an overlap. The simplest method is in the middle in terms of strength. Disadvantage - the total length of the two boards must be greater than the design length rafter leg. |
In this article we will look at the two simplest and most reliable splicing methods: butt and overlap. There is no point in touching the oblique cut; it is almost never used due to a large number of shortcomings.
Requirements of building codes and regulations for splicing rafters
Inept splicing of rafters along the length can not only sharply reduce their resistance to bending loads, but also cause complete destruction of the structure. The consequences of this situation are very sad. Building regulations provide certain patterns when choosing the size of the fastener, its installation location and the length of the pads. The data is based on many years of practical experience.
Spliced rafters will be much stronger if metal pins, rather than nails, are used to connect them. The instructions will help you make your own connection calculations. The advantage of the method is its versatility; it can be used to solve problems not only with lengthening rafters, but also with building up other roof elements. Specialized companies performed rough calculations and collected the data in a table, but it indicates only the minimum acceptable parameters.
- Diameter and length of studs. In all cases, the diameter of the studs must be ≥ 8 mm. Thinner ones do not have sufficient strength and are not recommended to be used. Why? IN metal connections The diameter of the studs is calculated based on tensile forces. During contraction metal surfaces They are pressed so tightly together that they are held together by friction. In wooden structures, the pin works in bending. Individual boards cannot be pulled together with great force; the washers fall into the board. In addition, as the relative humidity changes, the thickness of the boards changes, thereby reducing the tightening force. Studs used for bending must have big size. The specific diameter of the stud must be determined using the formula d w = 0.25×S, where S is the thickness of the board. For example, for a board 40 mm thick, the pin diameter should be 10 mm. Although this is all quite relative, you need to keep in mind the specific loads, and they depend on many factors.
- Board overlap length. This parameter should always be four times the width of the boards. If the rafter width is 30 cm, then the overlap length cannot be less than 1.2 m. We have already mentioned that specific solution accepted by the master taking into account the condition of the lumber, the angle of inclination of the rafters, the distance between them, weight roofing materials and climatic zone of the building location. All these parameters have a great influence on the stability of the rafter system.
- Stud hole spacing. It is recommended to fix the fasteners at a distance of at least seven stud diameters; the distance from the edge of the board should be at least three diameters. These are minimum values; in practice, it is recommended to increase them. But it all depends on the width of the board. By increasing the distance from the edge, you cannot reduce the distance between the rows of studs too much.
- Number of tie rods. There are quite complex formulas, but in practice they are not used. Craftsmen install two rows of studs, taking into account the distance between them, the holes are arranged in a checkerboard pattern.
Practical advice. To increase the bending strength of the spliced rafters, the holes of the studs should not be located on the same line; they should be shifted by at least one diameter.
Butt splicing with boards
It is much more convenient to do the work on the ground; prepare a flat area. Place the bars on the ground - the rafters will have to be trimmed, you need clearance for circular saw. Before splicing, find out exactly the length of the rafters. You need to measure it on the building; use any thin long boards, rope or construction tape. If there is an error of a few centimeters, no problem. When connecting the rafter legs on the roof, this error is eliminated without problems.
Step 1. Place one board on the bars, cut the end exactly at a right angle. It is better to cut with a hand-held electric circular saw.
Important. Follow the safety rules, this is a high-speed and very dangerous tool. Never remove the saw's factory safety features or turn off the electrical overload relays.
Rafter boards are quite heavy; when cutting, position them so that they do not pinch the saw blade or break prematurely during cutting. Prepare the second board in the same way. Make sure that the cut is only at a right angle. The ends of the spliced boards should fit tightly against each other over the entire surface; this is necessary to increase the strength of the spliced rafters. The fact is that even if the connection of the studs is loosened, the ends during bending will rest against each other along the entire length of the cut and hold the load. Studs and overhead boards will only keep the structure from creeping along its length.
Step 2. Place two prepared rafter boards side by side. Prepare a board for the overlay. We have already mentioned that its length should be approximately four times the width of the board. If the roof slopes have a slight slope, the distance between the rafters is large, and the roof will be insulated mineral wool, then the bending loads increase significantly. Accordingly, the length of the board for splicing must be increased.
Step 3. Place the overlay on two adjacent boards for the joint. Quite often, the thickness and width of boards, even from the same batch, differ by several millimeters. If this is the case, then level the boards on the side to which the sheathing will be nailed.
Practical advice. The science of strength of materials says that thinner material, the greater its resistance to bending along a thin plane. This means that, for example, five boards placed next to each other on an edge, each 1 cm thick, can withstand a significantly greater load than one board 5 cm thick. Conclusion - for splicing it is not at all necessary to cut thick expensive materials, you can use several thin pieces of the desired length. There are enough such pieces at any construction site.
Step 4. Drill holes for the studs in a checkerboard pattern and at standardized distances. To ensure that when drilling holes individual elements did not move, you need to temporarily fix them together. Use long and thin screws for these purposes; nailing is not recommended. They cut or tear the wood fibers, and the strength of the board is slightly reduced. Self-tapping screws do not cut the fibers, but push them apart; after unscrewing, the boards almost completely restore their original strength characteristics.
Step 5. Drill holes, do not place them on the same line, otherwise the boards may crack during use.
You may find recommendations to separate the boards after drilling the holes and lay jute between them to prevent the appearance of cold bridges. This is not only wasted work, but also harmful. Why? Firstly, no cold bridges arise at the splice points; on the contrary, they have the greatest thickness and, accordingly, the lowest thermal conductivity. But even if they appear, there will be no negative consequences it won’t, it’s a roof truss system, not room window or a door. Secondly, jute reduces the friction force between the splice elements, and this has a very negative effect on their strength. Thirdly, if condensation gets on the material, which is very likely, then it will take a very long time to remove moisture from it. What are the consequences of prolonged contact? wooden structures There is no need to tell about moisture.
Step 6. Insert the studs into the prepared holes, put washers on both sides and tighten firmly with nuts. It is recommended to tighten until the washers are pressed into the wood. The excess length of the studs can be cut off using a cylindrical grinder with a metal disc.
All other rafters are spliced in the same way.
Overlapping splicing
This connection is easier to make, but under one condition - the total length of the two boards allows it; it must be greater than the length of the rafter leg by the amount of overlap.
If you have low quality lumber, then before starting work it is recommended to lay it out on a flat surface and make an inspection. For long sections of spliced rafters, choose straight ones, and for segments use curves. Although for the rafter system it is strongly recommended to buy only quality materials, this is not an architectural element of a building on which you can save.
Step 1. Select the boards and place them on top of the beams. If you wish, you can align the ends using circular saw, no desire - don’t match. The condition of the ends does not in any way affect the strength of the overlap splice.
Step 2. Lay the boards on top of each other, adjust the length of the joint and overall size rafters.
Practical advice. The boards must lie strictly parallel to each other. Due to the fact that the upper one is raised above the lower one by the thickness of the material, stands made from pieces should be placed under it and the bars. The thickness of the segments should be equal to the thickness of the bottom board.
Step 3. Align the boards along one of the edges and temporarily fasten them with self-tapping screws. Drill holes, install studs, washers and tighten nuts.
Butt splicing with plywood
One of the ways to splice rafters helps to save boards and rationally use waste various lumber. IN in this case Cutting sheet plywood one centimeter thick is used.
Step 1. Lay the rafter boards evenly on the site, close the ends, pay attention to the parallelism of the side edges. The boards should be extremely equal in thickness, the ends should be cut exactly at right angles.
Step 2. Using a brush, generously coat the surface with PVA glue.
Step 3. Place the prepared piece of plywood at the joint and press it firmly with clamps. While fixing, make sure that the plywood does not move from its original location.
Step 4. Using long, strong self-tapping screws in a staggered pattern, screw the plywood to the boards. The length of the screws should be 1–2 shorter than the total thickness of the boards and plywood; their ends cannot protrude from reverse side. Be sure to place washers under the screws large diameter. Before tightening the screws, drill holes in the rafters. Their diameter should be 2–3 mm less than the diameter of the threaded part of the hardware.
Step 5. Turn the board over, place it under the ends of the stand, they should not hang in the air. Carefully remove all installed clamps one by one.
Step 6. Apply glue to the surfaces and place a second piece of plywood on them. Clamp it again with clamps.
Step 7 Tighten the screws with great force.
Important. When tightening the screws, make sure that they are not positioned against each other. The displacement must be at least three centimeters.
Step 8 Remove the clamps. To strengthen the splice assembly, tighten it with through pins. They should be placed in the same way as with conventional butt splicing.
Practical advice. The holes for the studs should be 0.5–1.0 mm smaller than the diameter of the stud. There are times when it is impossible to accurately select the diameter of a drill bit for wood. Then it is recommended to use a drill of a slightly smaller diameter, let the pin go in with a fairly large force.
During its hammering, the first few turns of the thread are crushed by strong blows of the hammer, which makes it very difficult to screw on the nut. To avoid problems, tighten the nuts before driving in the stud; now let the thread on the end kink; it is no longer needed. Before installing the rafters in place, check that the glue is dry. In good weather, it takes about 24 hours for it to completely harden.
The final touch is applying glue
Important. If, when splicing the rafters along the length of the boards, the nuts were tightened until the washer was sunk into the wood, then this cannot be done with plywood. Carefully control the pressing force, do not damage the plywood veneer.
How to correctly hammer nails into rafters when splicing
It is not always possible and necessary to splice individual rafter elements using studs; sometimes it is easier to do this with ordinary smooth nails. But you need to be able to hammer them in correctly, otherwise over time the compression force of the boards will decrease significantly. The length of the nail should be 2.5–3 cm greater than the thickness of the rafter at the junction.
How to correctly drive nails to connect loaded or critical wooden structures?
Step 1. Drive the nail into the boards at a slight angle, but not all the way. It is necessary that the tip protrudes from the back side by about one centimeter.
Step 2. On the back side of the rafter, bend the nail at a right angle with a hammer.
Step 3. Hammer the nail about one more centimeter. Bend the end again, the bend angle should now be much less than 90°. The more you bend it, the more secure the final fixation will be.
Step 4. Now you can drive the nail head all the way in. On the reverse side, bend the protruding part until the sharp end is completely inserted into the board. Remember that the point where the body of the nail exits and the point where its tip is driven in should not lie on the same line.
This technology completely eliminates the independent weakening of the pressing force.
It has already been mentioned that the bending strength of the rafters at the splice is always less than that of the whole element. If possible try to place this node as close as possible to the ridge, Mauerlat or various spacers. Such precautions minimize the risks of mechanical destruction of the rafter leg. If this possibility is not available for one reason or another, then it is not recommended to place the stop under the splice at a distance of more than 15% of the leg length from either end.
Never use black self-tapping screws for connections.. This metal has two significant drawbacks. The first is that it quickly oxidizes and loses its original strength. Secondly, the manufacturing technology of such self-tapping screws involves hardening. Hardened self-tapping screws when exceeding permissible load do not stretch, but burst. During roof operation relative humidity wooden structures change, and the thickness of the boards fluctuates accordingly. And this can significantly increase the tensile force of the self-tapping screw; it will not withstand it and will crack.
Do not overdo it with the amount of hardware. If there are too many of them, then the holes will significantly reduce the strength of the parts being connected, as a result you will get the opposite effect, the build-up will not be strengthened, but weakened.
Video - Splicing rafters along the length
