Making furniture with your own hands is becoming increasingly popular due to its high cost. finished products, and thanks to the large amount of source materials that have become freely available. At home, with a minimum set of appropriate tools, it is possible to assemble viable furniture that will serve well and delight you with its appearance. One of the most popular joining methods is gluing, which makes it possible to obtain durable, monolithic parts. Bonding can be used as an independent fastener or as a backup when using external elements such as dowels, dowels or screws.

DIY laminated wood

Before gluing, the parts are processed; this is done not only to clean the surface, but also to open the wood pores. When applied, the adhesive composition penetrates through the pores into the wood structure, into the intercellular space, and when hardened, it forms many thin threads (webs) that reliably “stitch” the workpieces together. The strength of a correctly executed seam exceeds the strength of the wood itself; when testing for fracture, the part breaks not at the gluing site, but along the whole wood.

Gluing wood allows you to obtain products with better parameters than solid ones. During the gluing process, elements that are suitable in texture and shade are selected, damaged, cracked and knotty areas are rejected. As a result, the glued parts have greater strength than ordinary ones, and by gluing the finest veneer onto the front surfaces, the products are given the appearance of the most valuable species. Wood glued according to all the rules is much less likely to warp, crack and dry out than solid wood.

How to glue wood. Technology

There are several ways to connect parts when gluing.

• Gluing wood into a smooth fugue - joining smooth parts without increasing the penetration area.

• Microthorn gluing – increasing the penetration area by 2.5 – 5 mm by creating a toothed relief on the part (using a milling cutter).

• Gluing to a serrated tenon – increasing the penetration area by 10 mm by creating a serrated tenon.

• Gluing to tongue and groove (tongue and groove, dovetail, oblique tenon) - additional grip due to the groove connection.

Although in certain situations where special conditions of use are expected, groove and tenon joints are relevant, in most cases the parts are glued together using a smooth fugue. Modern adhesive compositions penetrate deep into the structure and create a strong seam without additional wood removal.

How to glue boards together. Options

The wood to be glued must have a moisture content in the range of 8–12%, maximum 18%. If there is a need to glue wet parts, use special composition, as it hardens, it draws moisture out of the wood. When gluing blanks with different humidity A difference of more than 2% is not allowed to avoid internal stress in the adhesive seam due to deformation of the wetter part. The temperature of the workpieces being glued varies between 15 - 20⁰С, so work is carried out in warm rooms (18 - 22⁰С). In the cold, most compounds crystallize, which leads to a deterioration in the quality of gluing and complicates the process.

Final preparation of wood (planing, jointing, sanding) is carried out immediately before gluing in order to increase the permeability of the glue and avoid warping. It is important not only to select parts according to dimensions, structure and external data, but also to arrange them correctly.

• When gluing along the length, planks of only one type of sawing are used - tangential or radial;
• When gluing both along the length and width, alternation is not allowed different parts wood - the core is stacked with the core, sapwood (young, outer part) with sapwood;
• The annual rings of adjacent blanks made of boards or bars should be directed in different directions or at an angle to each other of 15⁰.

The standard thickness of furniture panels is 2 cm, but to glue wooden boards at home, when choosing boards for the board, the expected waste during processing is taken into account, so the workpiece is selected with a thickness of up to 2.5 cm. The excess will be removed during the initial processing, when eliminating defects, and after gluing, when sanding the board. If you dissolve for furniture board board 5 cm thick, you get two blanks with the same texture and shade, which increases the decorativeness of the product. For panels, boards of wood of the same species, up to 120 mm wide, are selected, so that it is possible to properly process the edges of the panel; the length of the blanks must have a margin (2 - 5 cm).

Adhesives

The adhesives used to make laminated wood are divided into two main groups.

Synthetic - obtained on the basis of resins or polyvinyl acetate dispersions (PVA). They are characterized by increased strength of the resulting connection, moisture resistance, and biostability. Disadvantages include the presence harmful substances, which can stand out in environment in the process of work and further exploitation. Compositions based on phenol-formaldehyde resins are “famous” for this. Modern PVA dispersions and their derivatives are non-toxic and are usually used in the domestic sphere and are considered universal for wood. The bulk of synthetic mixtures are ready for use. Epoxy glue needs finishing; to work with it, the hardener included in the kit is mixed with epoxy resin.

Natural mixtures - animal, plant, mineral. They are safe, provide a strong connection, but are produced in the form of semi-finished products that are prepared before use. How to glue wood with them: when preparing, you must strictly follow the instructions and observe the dosages, otherwise the quality of the glue will not allow you to obtain a strong connection. To prepare the glue, you usually need to dilute the powder concentrate with water to the desired consistency (it may require a certain period of swelling) or melt the solid particles. Direct exposure to fire is not allowed, “ water bath", on which the mass with the addition of water after swelling melts to a homogeneous consistency.

How to glue wood

When gluing wooden surfaces glue is applied to both parts in an even layer. The thickness of the layer depends on the type of glue, its consistency and the type of surfaces being glued - the thinner the wood, the thinner the layer. The glue should wet the part, but not excessively; when connecting the elements, an even bead should emerge outward. Glue drips are removed from the surface as soon as they set a little, using a scraper or spatula. Cured excess glue greatly spoils appearance parts and complicates their further processing.

How to glue a piece of wood.

After applying the glue, the parts are kept for a certain period of time, this allows the composition to penetrate deeper, at the same time excess moisture evaporates, and the concentration of adhesives increases. During exposure, the seam should not be exposed to wind or become dusty. Some varieties natural glue(bone, flesh) must be applied hot, instantly fastening the parts without aging, since as the composition cools, the composition loses its properties.

Wood gluing tool

To obtain the most durable connection, when gluing, the wood is pressed - subjected to compression using special presses. At home, improvised tools and means are used for these purposes - vices, clamps, cam devices, frames made of metal corners with clamping mechanisms. The pressure when pressing wood is maintained in the range from 0.2 to 1.2 MPa. In production, large values ​​are possible; at home, such indicators are enough for the structural parts to stick together.

Do-it-yourself laminated wood.

If the gluing technology is followed, the adhesive seam is strong and reliable, and, unlike the method of joining parts with metal fasteners, it does not spoil the appearance.

For those who like to create household items on their own, a topic is open on FORUMHOUSE. You can find out how to organize a convenient corner for working with wood in the article. The video about wooden elements in a country house shows interesting products, made by portal users.

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 by experienced builders or engineers with special training.

Designing a wooden rafter system is much more difficult than any metal structures. 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.

1. 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.
2. 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. A rather complex method that requires practical experience in carpentry. 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 position 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 for certain patterns when choosing the size of the fastener, the location of its installation and the length of the linings. 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.

1. 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 together so tightly 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. Bending pins must be large. 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.

   

2. Board overlap length. This parameter should always be four times the width of the boards. If the width of the rafters is 30 cm, then the length of the overlap cannot be less than 1.2 m. We have already mentioned that the specific decision is made by the master taking into account the condition of the lumber, the angle of inclination of the rafters, the distance between them, and weight roofing materials and climatic zone of the building location. All these parameters have a great influence on the stability of the rafter system.

   

3. 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.

   

   

4. 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 side by side, 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 required 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 the individual elements do not move while drilling holes, they need to be temporarily secured to each other. 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 flat surface and do an audit. 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 the overall size of the 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 methods of splicing rafters helps to save boards and rationally use waste of various lumber. In this case, cuttings of sheet plywood one centimeter thick are 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 times shorter than the total thickness of the boards and plywood; their ends cannot protrude from the 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 reverse side up, place the stands under the ends, 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 properly drive nails into rafters when splicing

It is not always possible or 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. Under small angle Drive the nail into the boards, 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. When the permissible load is exceeded, hardened screws do not stretch, but burst. During the operation of the roof, the relative humidity of wooden structures changes, 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 reverse effect, the build-up will not intensify, but weaken.

Video - Splicing rafters along the length

Types of connections of wooden structures

Typically, timber products such as beams, planks or planks come in a specific size, but construction often requires materials that are longer, wider or thicker. Therefore, to obtain the required dimensions, there are various types connections using notches, which are made manually according to markings or with special equipment.

Width connections

When joining narrow boards, boards of the required size are obtained.

There are several ways to connect.

1) Joint with a smooth reveal;
With this joining method, each strip or board is called a plot, and the seam that is formed as a result of the connection is called a fugue. The quality of jointing is indicated by the absence of gaps between the joints of the edges of adjacent plots.
2) Rail connection;
Grooves are selected along the edges of the plots and inserted into their slats, which fasten the plots together. The thickness of the slats and the width of the groove should not exceed 1/3 of the thickness of the board.
3) Quarter connection;
In plots that are fastened, quarters are selected along the entire length. In this case, the dimensions of the quarter, as a rule, do not exceed half the thickness of the plot.
3) Tongue and groove connection (rectangular and triangular);
This type of connection provides the plot with a groove on one side and a ridge on the other. The comb can be either rectangular or triangular, but the latter is rarely used as its strength is slightly inferior. The tongue and groove joint is quite popular and is often used by parquet manufacturers. The disadvantage of this connection is considered to be lower efficiency, since more boards are used.
4) Dovetail connection;

This type of fastening is a little similar to the previous one, only the comb has a trapezoidal shape. Well, hence the name.

Also, when assembling panels, dowels, tips in a groove and a comb are used with a lath glued into the end. Among the glued slats, there are triangular, rectangular and glued ones, and when using dowels, the dovetail groove is mainly chosen. All this is needed to securely fasten the shield.

Length connection

Popular types of joints along the length include: end-to-end, tongue-and-groove, tongue-and-groove, toothed adhesive joints, quarter joints, and rail joints. The toothed connection is the most popular because it has better strength.

There is also splicing, where longer sections are joined together. This can happen in several ways. For example, half-tree, oblique cut, oblique and straight overlay lock, oblique and straight tension lock and end-to-end. When choosing half-timber splicing, the required joint length should be 2 or 2.5 times the thickness of the timber. For greater reliability, dowels are used, for example, this can be found in the construction of cobblestone houses.

When using an oblique cut with trimming the end, the dimensions are 2.5 - 3 times the thickness of the beam and are also secured with dowels.

A connection with a straight or oblique patch lock is used in structures in which tensile forces are present. A straight rim lock is located on a support, and an oblique lock can be placed near the supports.

If you decide to use an oblique cut with an end trim, then the connection should have 2.5 or 3 times the thickness of the timber. In this case, dowels are also used.

When joining with a straight or oblique tension lock, you don’t have to worry about strength, but such a connection is difficult to manufacture, and when the wood dries out, the wedges weaken, so this joining method is not suitable for serious structures.

A butt splice is when the two ends of a beam are placed on a support and securely connected with staples.

The connection of beams or logs can be found during the construction of walls or in the upper or lower frame in frame houses. The main types of joints include half-tree, half-foot, tenon and corner frying pan.
Half-tree cutting is cutting down or cutting off half the thickness at the ends of the beams, after which they are connected at an angle of 90 degrees.

A half-foot joint is formed by cutting inclined planes at the ends of the beams, thanks to which the beams are tightly connected. The size of the slope is determined by the formula.
Cutting with a corner frying pan is very similar to cutting half a tree, but distinctive feature is that with such a connection one of the beams loses a small part in width.

Height connection

A cross-shaped connection of beams can be found during bridge construction. With this method, you can use a half-tree connection, a third and a quarter of a tree, or notching one beam.

Building up

Building up beams and logs is the connection of elements in height, which is often used in the construction of pillars or matches.

There are several types of extensions:

1) end-to-end with a hidden tenon;
2) end-to-end with a through ridge;
3) half-tree with bolt fastening;
4) half-tree with fastening with clamps;
5) half-wood with strip steel fastening;
6) an oblique cut with fastening with clamps;
7) end-to-end with overlays;
8) bolting;

The length of the joints is usually 2-3 times the thickness of the beams being connected or 2-3 times the diameter of the logs.

Tenon connection

When tenoning bars, a tenon is cut on one, and an eye or socket is made on the other. Tenon joints are often used to create joinery, doors, windows or transoms. All connections are made with glue. You can use not only one, but also two or more spikes. The more tenons, the larger the gluing area. This type of connection can be divided into corner end, corner middle and corner box.

With an angular end connection, an open through tenon (one, two or three), a tenon with a through and non-through darkening, and insert dowels are used. Corner middle connections can be found on doors. Corner middle and end joints can additionally use nails, screws, dowels or bolts.

Well, that’s probably all about connection types. This does not include connections made with nails, screws or bolts. Pure wood and a little glue. :)

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 rigidity when bending force is applied along the entire length of the element, the junction of the two parts of the rafter leg is 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 rafter, 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 inclined sections of the cutting are located is determined by the formula 2 × h.

The location for the joining section is found using the formula 0.15 × L, valid for all types of rafter frames, in which the value of 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, can simply be hammered into wooden parts.

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 the load-bearing capacity for each of the component 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 calculated 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. We should not forget about preliminary calculations and about preparing to make connections so that the result of the efforts is perfect.

Wooden parts are used in many products. And their connection - important process, on which the strength of the entire structure depends.

Dozens of wood products are used to make furniture and other wood products. various connections. The choice of method for connecting wooden parts depends on what the product should be like in the end and what load it should bear.

Types of connection

When connecting wooden parts need to remember important point- a thin part is always attached to a thick one, but not vice versa.

According to relative position elements, there are the following methods of connecting wooden parts:

• extension - increasing the height of a part;
• splicing - elongation of the workpiece;
• rallying - increasing the width of an element;
• knitting - joining at an angle.

The most common methods for joining wooden parts in furniture making are:

• gluing;
• "dovetail";
• end-to-end;
• grooved;
• overlap;
• deaf on spikes;
• through tenon.

Let's look at the technologies of some connections in more detail.

Length splicing

Such wooden parts have some nuances. At its core, this is the elongation of elements in the horizontal direction. Splicing can be:

• Butt-end - the ends are cut at right angles and aligned with each other. A bracket is hammered into both beams (logs).
• Oblique butt - the cuts are made at an angle, and the ends are fastened with a pin or nail.
• End butt with ridge.
• Direct overlay - the length of the cutting is 1.5-2 times greater than the thickness of the timber (log).
• Oblique overlay - the ends are cut at an angle and secured with bolts.
• Overlay with an oblique cut - at the ends of the parts, end ridges are made, having a width and length of one third of the thickness of the beam.

Increase in height

From the name it is clear that the essence is to lengthen the beams or logs in the vertical direction. The axes of the elements are on the same vertical line. Types of extensions are:

• End-to-end extension. To absorb random loads, a barbed pin is inserted on the sides.
• Extension with one or two spikes. The width and height of one tenon must be at least one third of the thickness of the timber. The depth of the nest is slightly greater than the height of the spike.
• Half-tree extension. The ends of both logs need to be cut to half their thickness by 3-3.5 diameters in length.
• Tongue building. In one beam you need to cut a fork into which you need to insert the correspondingly cut end of another piece. The connection itself must be wrapped in tin.

Width joining

Used to increase the width of the product. When using bonding methods, it is important to pay attention to the location of the tree’s annual rings. It is important to alternate the boards depending on their direction. The payment options are:

• Butt-to-end - the parts need to be trimmed and jointed using a square.
• In tongue and groove - the height and width of the ridge is equal to 1/3 of the thickness of the board.
• Using a hacksaw, the edges must be cut at an acute angle to the wide plane of the board.
• With a comb with a height of 1/3 to half of the board.
• A quarter with a ledge equal to half the thickness of the board.
• In tongue and groove with slats - in each board, select grooves into which you need to insert a rake that is twice as wide as the depth of the groove.

Mating

Knitting is used when there is a need to connect parts at an angle. Types of knitting are:

• half-tree knitting using a hidden spike;
• half-paw mating;
• single and double slotted tenons;
• slotted paw.

to the end

The easiest way to join two parts together. Joining wooden parts at right angles is done using this method. The surfaces of the two parts are carefully adjusted to each other and pressed tightly. The wooden parts are connected with nails or screws. Their length should be such as to pass through the first part and go deeper into the second by about 1/3 of the length.

In order for the fastening to be reliable, it is necessary to drive in at least two nails. They need to be located on the sides of the center line. The thickness of the nail should not cause cracking of the wood. Therefore, it is recommended to make holes in advance with a diameter of 0.7 of the thickness of the nail used.

To enhance fixation, lubricate the surfaces that are connected with glue. For rooms that will not be exposed to moisture, you can use carpentry, casein or hide glue. If the product is used in conditions of high humidity, it is better to use moisture-resistant glue, for example, epoxy.

T-shaped connection with overlay

To make such a connection of wooden parts, you need to place one piece on top of another and fasten them to each other using bolts, screws or nails. Wooden blanks can be placed either at a certain angle to each other or along one line.

To ensure that parts do not change, use at least 4 nails. If there are only two nails, then they are driven in diagonally. To make the fixation more durable, the nails must pass through both parts, and the protruding ends must be bent and deepened into the wood.

Half-tree connection

To perform such a connection between two wooden parts, certain skills and experience are required. It is performed as follows. In both workpieces, samples are made with a depth that corresponds to half their thickness. The width of the selection must be equal to the width of the part.

The method of joining wooden parts in half a tree can be done using different angles. In this case, it is important to ensure that the angle is the same on both wooden blanks, and the width corresponded to the width of the part. Thanks to this, the parts are pressed tightly against each other, and their edges are located in the same plane.

In addition, such a connection can be complete or partial. In the case of a partial connection, the end of one workpiece is cut at a certain angle, and a corresponding cut is made at the end of the other. Such joints include angular half-tree joints. The idea is to trim both tenons at an angle of 45°, as a result of which the seam between them is located diagonally. When using this method, you need to be especially careful and make corner cuts special tool- miter box.

Cleat

Such wooden parts are used for fastening sheathing boards or when laying floors. The edge of one board has a tenon, and the edge of the other has a groove. Accordingly, fastening occurs when the tenon enters the groove. This connection looks very neat, since there are no gaps between the boards.

Doing tenons and mortises requires some experience. And besides, for production you will need special machine. Therefore, it is easier to purchase ready-made parts.

Connection "socket-spike"

The most commonly used method of joining wooden parts. This joint is strong, rigid and looks as neat as possible. To make such a connection, you need to have some skills and experience, as well as be careful. An incorrectly made socket-tenon connection is fragile and looks unsightly.

Its essence is as follows. At the end of one workpiece a groove is drilled or gouged out, and at the end of the other - a tenon. It is better when the elements have the same width. If the thickness is different, then the tenon is made in a thin part, and the groove, accordingly, in a thick one.

Spike connection sequence:

• Using a thicknesser, draw two marks parallel to each other on the side of one workpiece. The distance should be the width of the future spike. To ensure its evenness, markings should be made on both sides.
• Most optimal tool to make tenons - a hacksaw with a narrow blade and fine teeth, or bow saw. During operation, the teeth of the tool must pass along the inner edge of the marking line. For convenience, it is better to clamp the part in a vice. It is best to make the spike slightly larger than the required size. Then, if necessary, you can remove the excess. But if the spike turns out to be shorter, then the whole process will need to be repeated again.
• Using a chisel or chisel, a socket (groove) is made in the second part. Naturally, the dimensions of the groove must correspond to the dimensions of the tenon. It is best to drill holes around the entire perimeter of the groove before starting chiselling. The edges are carefully processed with a chisel.

If the connection of wooden parts is done correctly, then the surfaces of the edges of the tenons fit tightly to the walls of the nest. This gives good adhesion when gluing. To make the fit of the studs tighter, their dimensions should be 0.2-0.3 mm higher more sizes nests If this value is exceeded, the bowstring may split; if the tolerance is less, the fastening will lose its strength during operation.

In addition, such a connection also involves gluing and fastening with screws, nails or wooden dowels. To simplify the work, you should drill holes before screwing in the screws. The screw heads are hidden in a countersunk (made using a countersink). The pilot hole should be equal to 2/3 of the diameter of the screw and 6 mm (approximately) less than its length.

Bonding

Gluing wooden parts is carried out as follows:

• The surfaces to be glued are cleaned with a lint-free cloth, and rough spots are smoothed out with fine sandpaper.
• Using a cardboard stick, apply wood glue in an even, thin layer over all necessary surfaces.
• Surfaces coated with glue should be rubbed against each other. This will ensure even contact and strong adhesion.
• The parts need to be pulled together to ensure reliable retention at the joints. Measuring the diagonals will make sure that the angles are straight. They must be equal. If this is not the case, the position of the elements needs to be corrected.
• The connection is strengthened by drilling pilot holes into which finishing nails or screws are driven. The screw heads must be recessed; for this, the holes must be bored out. The nails are deepened using a punch.
• Holes with nails are covered with wood putty. The holes bored out for the screws are closed with hardwood wooden plugs coated with glue. When the glue or putty has dried, the surface is sanded so that it is smooth and then varnished.

Necessary tools and equipment

The tools for execution are very diverse. They are selected depending on the type of work performed. Since in carpentry the elements being processed are larger than in carpentry, therefore, the tool must be suitable.

To connect wooden parts use the following:

• axe;
• plane, straight and curved planes, bear, sherhebel - more thorough surface treatment;
• chisel - chiseling holes and sockets;
• chisel - for cleaning cuts;
• drills with different tips - for through holes;
• various saws- for sawing lengthwise and crosswise;
• hammer, hammer, sledgehammer, mallet;
• square, compass, level and others auxiliary tools;
• nails, metal staples, bolts with nuts, screws and other fastening products.

Conclusion

In fact, there are many more ways to connect wooden parts of furniture or other structures. The article describes the most popular methods and technologies of implementation. It is important to remember that the connection of wooden parts for painting or varnishing must be carefully prepared, and all fastenings must be strong and made conscientiously.