The coolest joiners and carpenters are said to be able to build a house without a single nail. Japanese artisans, even amateurs, are just that.
A few years ago, a young and passionate automotive industry worker came across a book describing traditional Japanese woodworking techniques. He was very fascinated by the descriptions of the connections of parts without the use of nails, screws and glue. He wanted to learn how to do the same. But there were no diagrams for making fasteners in the book. Then the guy decided to draw them himself.
He used the free service Fusion-360 to model and animate the parts. The Japanese translated the resulting result into GIFs and posted it on a Twitter account called The joinery... In almost a year, the young carpenter visualized 85 different types of detachable connections.
The variety of mounts is truly amazing. With their help, you can make basically anything - a stool, a sofa, a table, and so on. The main thing is to have straight arms and a good, preferably electric tool.
But even if the manual labor doesn't inspire you at all, you will probably enjoy watching GIFs. The grace with which the details mesh with each other is mesmerizing.
Timber such as beams, planks or squared beams are generally produced in a specific size, but often construction may require material that is long, wide, or thick. For this reason, to achieve the required size, several types of joints are used with the use of cuts made by specialized equipment or by manual marking.
Width connections
After bonding boards with a small width, a shield is obtained with the dimensions required for production. There are several methods for docking:
1)Docking on a smooth joint;
in this method of joining, any board or rail is referred to as a plot, and the formed seam is referred to as a fugue. The jointing can be considered qualitative only when there are no gaps between the edges of adjacent boards.
2)Rail fastening;
grooves are selected along the edges of the plot and slats are inserted into them, fastening the boards between each other. The indicator of the thickness of the lath and the indicator of the width of the groove itself cannot exceed 1/3 of the indicator of the thickness of the timber used
3) Binding in a quarter;
in abutting plots, completely along the entire length, quarters are selected. With this method, quarters cannot exceed 50% of the thickness of the plot itself.
4) Docking type in groove and ridge (rectangular and triangular);
this type of joining provides for the presence of a groove on one edge of the plot, and on the opposite edge of the ridge, the shape of which can be either rectangular or triangular. Moreover, the latter is rarely used, due to the lower level of fortress. This kind of joining is quite in demand and is often used in the manufacture of parquet. Lack of bonding - less economy due to the use of more boards
5) Dovetail fastening;
This type of docking is somewhat similar to the previous version, but only the ridge here has a trapezoid shape, similar to the tail of swallows. Hence the name of the fastening method.
Joining the boards into shields: a - on a smooth joint, b - in a quarter, c - on a rail, d - in a groove and a rectangular ridge, e - in a groove and a triangular ridge, e - in a “dovetail”.
Also, in the production of wood panels, dowels, a ridge glued into the end strip and tips in the groove are often used. The laths for gluing can be rectangular or triangular. When using dowels, it is better to prefer the dovetail groove. All this is necessary for the manufacture of high quality wood panels.
Shields: a - with dowels, 6 - with a tip in the groove and ridge, c - with a glued strip in the end, d - with a glued triangular strip, d - with a glued triangular strip.
Length splice
The most popular methods of joining along the length are: close, such as groove and comb, fastening with a "mustache", serrated type of adhesive fastening, quarter, and also fastening on a rail. The docking of the toothed type is most actively used, due to its extremely high level of strength.
The connection of the bars along the length: a - end-to-end, b - in the groove and comb, c - on the mustache, d, e - on the toothed adhesive joint, e - in a quarter, g - on the rail.
Also, the boards can be joined by the splicing method, when the segments of the timber dock together in length. This is done in several ways. For example, in half a tree or with a cut of an oblique type, an overhead lock of an oblique type and a straight one, close, as well as a tension lock of both a straight type and an oblique one. When splicing using the half-tree method, the required length must be 2-2.5 times the thickness of the bar. To increase the level of reliability, dowels are used. For example, a similar option can be observed when building log cottages.
When using an oblique cut with cutting ends, the size should be equal to 2.5-3 of the thickness of the bar. It is also fixed by means of pins.
Fastening with an oblique or straight type patch lock is used in those structures where there is a tensile force. The direct-type overhead lock is placed directly on the support itself, and the oblique type lock can be placed at the support.
If you made a decision to use an oblique cut with trimming the ends, then the fastening must be 2.5-3 of the bar thickness indicator. In such situations, you can also use a dowel.
When fastened by means of an oblique or straight type tension lock, a high level of strength is achieved. But at the same time, such a docking is notable for the complexity of manufacturing, and the wedges are somewhat weakened when the tree dries out. For these reasons, this method of fastening will not work for structures that carry high loads.
Side-by-side splicing involves moving both ends of the bar onto a support and then stapling it together.
Splicing: a - in a half-wood, b - with an oblique cut, c - a straight patch lock, d - an oblique patch lock, e - a straight tension lock, e - an oblique tension lock, g - end-to-end.
The fastening of logs or beams can be observed when erecting the walls of frame houses, in the upper or lower part of the harness. The key types of fasteners are: half-wood, corner pan, spike type and half-leg.
Docking in a half-tree - direct cutting or cutting of 50% of the thickness at the edges of the bars, as well as their subsequent fastening at a right angle.
The half-leg docking is formed by cutting at the edges of the beams of the inclined planes, as a result of which a tight connection of the beams is obtained. The slope must be determined using a special formula.
The cut by means of a corner frying pan is extremely similar to the cut by the half-wood method, but differs from it in that with this type of fastening, one of the bars loses a little in width.
The connection of the bars at an angle: a - half-wood, b - half-leg, c - spike, d - angular.
Height connection
Cross-shaped fastening of the bars is often observed during the construction of bridge structures. With this option, you can use the docking in half a tree, by a third and a quarter, and also by notching only one of the bars.
Cross-shaped connection of the beams: a - in half a tree, b - in a third of a tree, c - in a quarter of a tree, d - with a notch of one bar.
The method of building boards or bars in height is called bonding materials in height, which is very actively used when erecting poles or masts.
Build-up is subdivided into the following types:
- Tightly with a secret type thorn.
- Tight with a through-type ridge.
- Half-wood bolted.
- Half-tree with fastening on clamps.
- Half a tree with a steel strip.
- An oblique cut with fastening on clamps.
- Tightly with overlays.
- Fastening with bolts.
The length of the joints themselves, as a rule, is equal to 2/3 of the thickness of the joined bars or 2/3 of the diameter of the logs.
Connection of logs when building up: a - end-to-end with a secret spike, b - end-to-end with a through ridge, c - half-wood with fastening with bolts, d - half-wood with fastening with strip steel, d - half-wood with fastening with clamps, e - oblique cut with fastening with clamps, g - back to back with overlays and bolted.
Spike connection
When fastening the bars by means of thorns, a direct thorn is cut on one of them, and an eyelet or a socket is made on the other. Knitting of beams with a thorn method is actively used in the production of such joinery as doors, windows or transoms. Each fastening is carried out on the basis of glue. It is allowed to use not only one thorn, but several. The larger the number of spikes is planned to be made, the correspondingly and larger the gluing area will be.
This type of docking is subdivided into: corner end type, corner middle type and corner box type.
When the end-type angular fastening is used, unclosed through thorns (no more than three), thorns with darkness through and blind type, as well as a plug-in dowel. Corner docking of the middle type is quite often found on doors. For corner fasteners of the middle and end type, you can additionally use screws, nails or bolts.
Corner middle joints on the tenon: a - blind type US-1, b through US-2, c - through double US-3, d - blind into the groove and comb US-4, e - blind into the groove US-5, e - blind on round dowels US-6.
That's all the key information about the existing connection types. This does not include nails, screws or bolts. Pure wood and a little bit of glue. 🙂
Wooden parts are used in many products. And their connection is an important process on which the strength of the entire structure depends.
Dozens of different compounds are used to make furniture and other wood products. The choice of the method of joining wood parts depends on what the product should be in the end and what kind of load it should carry.
Connection types
When connecting wooden parts, an important point must be remembered - always a thin part is attached to a thick one, but not vice versa.
According to the mutual arrangement of the elements, the following methods of joining wood parts are distinguished:
- building - increasing the height of the part;
- splicing - elongation of the workpiece;
- rallying - increasing the width of the element;
- knitting - connection at an angle.
The methods of joining wooden parts in the manufacture of furniture are most often used as follows:
- gluing;
- "dovetail";
- end-to-end;
- groove;
- overlap;
- deaf on thorns;
- through spike.
Let's consider the technologies of some compounds in more detail.
Splice lengthwise
This kind of wooden parts has some nuances. In essence, this is the elongation of elements in the horizontal direction. Splicing can be:
- End-to-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 a comb.
- Straight overlay - the cutting length is 1.5-2 times greater than the thickness of the bar (log).
- Oblique pad - the ends are cut at an angle and fixed with bolts.
- A lining 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 bar.
Height extension
From the name it is clear that the essence lies in lengthening the beams or logs in the vertical direction. The axes of the elements are on the same vertical line. The types of building are as follows:
- Build-up end-to-end. A barbed pin is inserted at the sides to absorb accidental loads.
- Extension with one or two thorns. The width and height of one spike must be at least one third of the thickness of the bar. The depth of the nest is slightly more than the height of the thorn.
- Growing in half a tree. The ends of both logs must be cut to half their thickness by 3-3.5 diameters in length.
- Build up the tongue. In one beam, you need to cut a fork into which you need to insert the correspondingly cut end of another workpiece. The connection itself must be wrapped in tin.
Rallying in width
Used to increase the width of the product. When using rallying 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. Rallying options are as follows:
- End-to-end - details need to be cut and squared in a square.
- In tongue and groove - the height and width of the ridge is equal to 1/3 of the thickness of the board.
- In a hacksaw - the edges must be cut at an acute angle to the wide plane of the board.
- 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 the groove with strips - in each board, select the grooves into which you need to insert a strip that has a width twice the depth of the groove.
Knitting
Knitting is used when it becomes necessary to join parts at an angle. Types of knitting are as follows:
- knitting in half a tree using a secret thorn;
- knitting in a half-paw;
- single and double slotted tenons;
- slotted paw.
to the butt
The easiest way to put two pieces together. Right angle joining of wood pieces is done using this method. The surfaces of the two parts are carefully matched to each other and pressed tightly. Wooden parts are connected with nails or screws. Their length should be such as to pass through the first part and go deep into the second by about 1/3 of the length.
For the fastening to be reliable, it is necessary to drive in at least two nails. They need to be placed on the sides of the center line. The thickness of the nail should not cause the wood to crack. Therefore, it is recommended to pre-make holes with a diameter of 0.7 of the thickness of the nail used.
To enhance fixation, grease the surfaces that are connected with glue. For rooms that will not be exposed to moisture, you can use carpentry, casein or skin glue. In the case of using the product in high humidity conditions, it is better to use a moisture-resistant glue, for example, epoxy.
Overlay T-joint
To make such a connection of wooden parts, you need to lay one workpiece on top of another and fasten them to each other using bolts, screws or nails. You can arrange wooden blanks both at a certain angle to each other, and along one line.
To keep the details from changing, use at least 4 nails. If there are only two nails, then they are driven in diagonally. For a stronger hold, the nails must go through both parts, and the protruding ends must be bent and deepened into the wood.
Half-tree connection
To make such a connection of two wooden parts, certain skills and experience are required. It is performed as follows. In both blanks, samples are made with a depth that corresponds to half of their thickness. The sampling width must be equal to the part width.
The method of joining wooden parts in half-wood can be performed at different angles. In this case, it is important to ensure that the angle is the same on both pieces of wood, and the width matches the width of the part. Due to this, the parts are tightly pressed against one another, 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 blank is cut at a certain angle, and at the end of the other, a corresponding cut is made. Such compounds include an angular mustache in a half-tree. The bottom line is to trim both studs 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 the corner cuts with a special tool - a miter box.
Cleat
Such wooden parts are used for fixing planks or for flooring. The edge of one board has a spike, and the edge of the other has a groove. Accordingly, the fastening occurs when the tenon enters the groove. This connection looks very neat, since there are no gaps between the boards.
Making tenons and grooves takes some experience. And besides, a special machine is required for manufacturing. Therefore, it is easier to purchase ready-made parts.
Socket-tenon connection
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 attentive. An improperly made socket-tenon connection is fragile and looks ugly.
Its essence is as follows. At the end of one workpiece, a groove is drilled or hollowed out, and a spike at the end of the other. It is better when the elements are of the same width. If the thickness is different, then the spike is made in a thin part, and the groove, respectively, in a thick one.
Spike Sequence:
- Using a thickness gauge, draw two parallel lines on the side of one workpiece. The distance should be the width of the future spike. For its evenness, markings should be made on both sides.
- The most optimal tool for making thorns is a hacksaw with a narrow blade and fine teeth, or a 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 is 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 along the entire perimeter of the groove before starting chiselling. The edges are neatly cut with a chisel.
If the connection of the wooden parts is done correctly, then the surfaces of the edges of the thorns adhere tightly to the walls of the nest. This gives good adhesion when gluing. In order for the thorns to fit more tightly, their dimensions should be 0.2-0.3 mm larger than the socket dimensions. If this value is exceeded, the bowstring may split; if the tolerance is less, the mount will lose its strength during operation.
In addition, such a connection also involves gluing and fastening with screws, nails or wooden dowels. To simplify work, holes should be drilled before screwing in the screws. The heads of the screws are hidden in a recessed hole (made with a countersink). The pilot hole should be 2/3 of the screw diameter and less than 6 mm (approximately) of its length.
Gluing
The gluing of wooden parts is carried out as follows:
- The surfaces to be glued are cleaned with a lint-free cloth, and roughness is smoothed with fine emery.
- Using a cardboard stick, apply the joiner's glue in an even thin layer over all necessary surfaces.
- Glue-smeared surfaces should be rubbed against each other. This will provide an even touch and a strong bond.
- The parts must be pulled together so that the retention at the joints is reliable. Measurement of the diagonals will make sure that the corners 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. The nails are deepened using a punch.
- Holes with nails are covered with wood putty. The holes bored for the screws are closed with hardwood plugs, greased with glue. When the glue or putty is dry, the surface is smoothed with emery so that it is smooth and then varnished.
Required tools and fixtures
The tools for execution are very diverse. They are chosen depending on the type of work performed. Since in the carpentry the processed elements are larger than in the joinery, accordingly, the tool must be suitable.
To connect wooden parts, use the following:
- axe;
- planer, straight and curved planes, bear, scherhebel - more thorough surface treatment;
- chisel - chiselling holes and sockets;
- chisel - for cleaning cuttings;
- drills with different tips - for through holes;
- various saws - for sawing up and down;
- hammer, hammer, sledgehammer, mallet;
- square, compass, level and other auxiliary tools;
- nails, metal staples, bolts with nuts, screws and other products for fastening.
Conclusion
In fact, there are many more ways to connect wooden pieces of furniture or other structures. The article describes the most popular execution methods and technologies. It is important to remember that the connection of wooden parts for painting or varnishing must be carefully prepared, and all fasteners must be strong and made to last.
It will be useful for novice home craftsmen to learn about the methods of joining wooden parts. We devote a short educational program to this topic, which will describe the main types of joinery joints and rallies with the use of glue, nails, screws or dowels, or without them at all.
Rules for choosing a connection depending on the type of load
The most simple end connections, they are used when it is necessary to build up a part. These joints are best suited to withstand compressive loads, but good resistance to twisting, stretching and bending can be achieved by cutting down specially shaped locks. The standard end connection is trimmed to half the thickness of both parts. The cut can be straight or oblique; if necessary, to prevent bending, stretching or twisting, a thorn or an obtuse angle is cut at the end of each cut, or the cut is made stepwise, forming a kind of "lock".
1 - a straight overlay in a half-tree; 2 - oblique pad; 3 - straight strip with a stepped joint; 4 - half-wood pad with an oblique joint; 5 - oblique patch lock; 6 - half-wood connection with an oblique thorn
Corner and side joints are used to connect straight parts into a truss or frame. Usually this part of the structure is a supporting one, so the main loads fall on displacement and compression. If the structure is subjected to the stipulated static load, a rectangular tenon is cut on one of the parts, and a groove or eyelet of appropriate dimensions is cut on the other. If action to break the structure is possible, the tenon and the groove are cut in the form of a trapezoid.
Corner joints: 1 - with an open through thorn; 2 - with a deaf closed thorn; 3 - with a through oblique thorn
Overhead cross and T-shaped connections are used, as a rule, for additional connections between critical structural parts. The main load in them is on compression, displacement and rupture. The first two types of loads are eliminated by cutting half a tree or less, followed by aligning the parts. The shoulders of the notches take the main load on themselves, it remains only to secure the connection with screws or overhead brackets. In some cases, a dowel is used to strengthen the connection or a thorn with a wedge is cut out.
1 - cross connection with a half-wood overlay; 2 - cross connection with landing in one socket; 3 - T-shaped connection with a hidden oblique thorn; 4 - T-shaped connection with a straight stepped plate
A separate type of connections is box-type. They are intended for joining boards at right angles. Usually, for a box connection, teeth are cut on each board, the width of which is equal to the distance between them. On different boards, the teeth are cut with an offset, so when joining, the corner from the boards looks like one whole. The teeth can also be wedge-shaped, which prevents the angle from breaking in one direction, or they are additionally fastened with glue or nails.
Box corner joints: 1 - with straight through thorns; 2 - with oblique through thorns
How to make a spike connection
To make a tenon joint, you need to circle both parts with a marking line on all faces at a distance from the end equal to the width of the joint. On two opposite sides and the end, the body of the thorn is marked with lines, the markings on both parts are completely identical.
The thorn is trimmed from the sides with a hacksaw for a cross-cut and the wood is chipped with a chisel. The width of the stud is made 2-3 mm larger for subsequent precise processing with a knife or chisel. The groove is cut with a hacksaw for longitudinal cutting and chipped with a chisel, also leaving a small allowance for processing. This is followed by fitting, in the process of which the parts are combined and achieve the most snug fit.
With a T-shaped spike connection, a central spike or groove is cut on one of the parts, and an eyelet is hollowed out on the other, or two side cuts are made, depending on the type of the first part. To make the eyelet, a chisel is used, turning the inclined part of the blade into the hole. If the eyelet is not solid, I make the spike 8-10 mm more depth and cut off its end in the form of a deployed wedge. So, when hammering, the spike will open itself, and the part will be firmly seated.
To connect wide parts, you can use the box connection by cutting several pins and grooves. The easiest way to secure a tenon joint is to drill through the tenons and hammer a wooden dowel into the hole (window gusset).
How to splice boards with glue
A very popular method of joining planks and planks is longitudinal and transverse gluing. When joining the boards with the wide side, the end can be even, although in most cases a tongue-and-groove profile is used. A tight fit of the parts is very important so that the adhesive layer is as thin as possible, this is the only way to achieve maximum strength. Sometimes a small amount of cotton fiber is applied to the butt, greased with glue, this improves the quality of the adhesion.
The boards can also be connected in profile, but this will require wedge-shaped toothed cutting of both ends with an offset to the floor of the tooth for different parts. At home, such an operation can be performed using a hand-held router.
For gluing parts, casein glue or high concentration PVA is used; sifted wood flour is added to the adhesive to give strength. The surfaces are covered with glue and kept in air for 3-5 minutes, after which they are placed under oppression or squeezed with clamps. Such a connection turns out to be stronger than the tree itself and never breaks at the joint.
How to weld structural members
For supporting structures, two types of connections are used - extension and articulation. The easiest way to weld the two pieces together is to make a half-thickness cut with a hacksaw at the same distance from the ends, and then chop off the excess wood with an ax. After matching the two parts, the connection is usually fastened with two overhead strips nailed to the side of the cut. Bonding is also possible, but only with a tight fit of the parts.
The ends cut into half a tree can be brought together at almost any angle, this is the main method of connecting roof trusses. For fastening the parts, an additional tightening bond is required: the bar is applied to the connected parts from the side at a distance of 30-50 cm from the corner and cut into half the thickness at the points of contact, and then the structure is fastened with nails.
Often vertical and inclined structures need support, for example, when connecting a rafter system to floor beams. In this case, a notch is made for the seats on the horizontal beam, into which the racks will be inserted. It is very important to observe the angle of inclination and make the undercut by no more than a third of the thickness of the timber.
Connections with ad hoc links
Almost all joinery joints are made with additional reinforcing ties. In the simplest example, the role of such is played by nails or self-tapping screws.
When building up parts, the unit can be strengthened with a through bolt connection, clamps, brackets and wood grouses, or it is simply wrapped with cold-rolled wire. It is enough to fasten the spliced vertical supports with two overhead strips - wooden or metal.
Corner joints are most often fastened with staples, patch plates or corners. In cases where it is necessary to maintain a small mobility of the connection, one through bolt is used, which either stitches across the place of the overlay of the parts, or pulls them in the longitudinal direction with a minimum indent from the overlay.
The attachment point of the special connection must be at least 10 diameters of the fastening element from the edge and must not have any defects. It is important to remember that often the bonds do not provide the overall strength of the joint, but only compensate for the unaccounted load.
The rafter system is the most complex and one of the most critical elements of the house; the comfort and operation time of the structure largely depends on the correctness of its construction. Calculation and design of the rafter system should only be done by experienced builders or engineers with special training.
It is much more difficult to design a wooden truss system than any metal structure. Why? In nature, there are no two boards with exactly the same strength indicators; this parameter is influenced by a lot of factors.
The metal has the same properties, which depend only on the grade of steel. The calculations will be accurate, the error is minimal. With a tree, everything is much more complicated. In order to minimize the risks of destruction of the system, it is necessary to provide a large margin of safety. 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 essential.
Prices for various types of building boards
Construction boards
Why splicing rafters
There are several reasons why you need to splice rafters.
- Roof length exceeds standard lumber length... The standard length of the boards does not exceed six meters. If the slope is large, then the boards will have to be lengthened.
- During construction, there are many good boards with a length of 3-4 m... To lower the estimated cost of the building and reduce the amount of unproductive waste, you can use these pieces to make the rafters after splicing them together.
Important. It must be remembered that the strength of spliced rafters is always lower than that of whole ones. You need to try to place the splice as close to the vertical stops as possible.
Splicing methods
There are several methods of splicing, definitely no better or worse. Craftsmen make decisions based on their skills and the specific location of the joint.
Table. Methods for splicing rafters.
| Splicing method | Brief description of technology |
|---|---|
| It is used on boards with a thickness of at least 35 mm. Quite a complex method, it requires practical experience in performing carpentry work. In terms of strength, the connection is the weakest of all. The advantage is saving lumber. Practically at construction sites it is used very rarely. |
| The length of the rafter legs is increased by means of an overlay. The cover can be wooden or metal. If the length of two pieces of boards is insufficient in terms of the parameters of the rafter system, then this method allows them to be increased. The butt joint has the highest flexural strength and is widely used during the construction of various structures. |
| Overlap. Two boards are fixed with an overlap. The simplest method, in terms of strength, takes the middle position. Disadvantage - the total length of the two boards must be greater than the design length of the rafter leg. |
In this article, we will look at two of the 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 the large number of shortcomings.
Building code requirements for joining rafters
Inexperienced splicing of rafters along the length can not only sharply reduce their resistance to bending loads, but also cause the complete destruction of the structure. The consequences of this situation are very sad. Building rules provide for certain patterns when choosing the size of fasteners, their installation locations and the length of the overlays. The data was taken based on many years of practical experience.
Spliced rafters will be much stronger if you use metal studs instead of nails to connect them. The instruction will help you make an independent calculation of the connection. The advantage of the method is its versatility, with its help it is possible to solve problems not only with lengthening the rafters, but also with building up other elements of the roof. Specialized companies performed rough calculations and collected the data in a table, but only the minimum allowable parameters are indicated in it.
- Diameter and length of studs... In all cases, the diameter of the studs must be ≥ 8 mm. The thinner ones do not have sufficient strength, and it is not recommended to use them. Why? In metal joints, the diameter of the studs is calculated for the tensile forces. During tightening, the metal surfaces are pressed against each other so strongly that they are held by frictional force. In wooden structures, the stud works in bending. Individual boards cannot be pulled together with great force; the pucks will fall into the board. In addition, during the change in the relative humidity of the boards, the thickness is changed, due to this, the pulling force is reduced. Bending studs should be oversized. The specific diameter of the stud must be determined by the formula d w = 0.25 × S, where S is the thickness of the board. For example, for a 40 mm thick board, the stud diameter should be 10 mm. Although this is all relatively relative, you need to keep in mind the specific loads, and they depend on many factors.
- Overlap length of boards... 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 a 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, the weight of the roofing materials and the climatic zone of the location of the building. All these parameters have a great impact on the stability of the rafter system.
- Stud hole spacing... It is recommended to fix the fasteners at a distance of at least seven diameters of the studs; the distance from the edge of the board should be at least three diameters. These are the minimum indicators, in practice it is recommended to increase them. But it all depends on the width of the board. It is impossible, by increasing the distance from the edge, to 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. The craftsmen install two rows of pins, taking into account the distance between them, the holes are staggered.
