Joining a beam along the length. The design of the floor on wooden beams, the calculation of the bearing capacity. Splicing, strengthening and warming. Inter-beam filling of the floor
A myriad of connections can be used to connect wooden parts. The names and classifications of carpentry joints tend to vary significantly by country, region, and even school of woodworking. The craftsmanship lies in the fact that the precision of execution provides a correctly functioning connection that is able to withstand the loads intended for it.
Initial information
Connection categories
All connections (in carpentry they are called bindings) of wooden parts according to the scope can be divided into three categories (foreign version of the classification):
- box;
- frame (frame);
- for splicing/splicing.
Drawer connections are used, for example, in the manufacture of drawers and cabinets, frame connections are used in window frames and doors, and rallying / splicing is used to obtain parts with an increased width / length.
Many joints can be used in different categories, for example, butt joints are used in all three categories.
Material preparation
Even planed lumber may need some preparation.
- Trim the material with a margin in width and thickness for further planing. Don't cut to length yet.
- Choose the best quality layer - the front side. Plane it along the entire length. Check with a straightedge.
After the final alignment, make a mark on the front side with a pencil. - Plane the front - clean - edge. Check with a straightedge, as well as a square against the front side. Smooth out warp by planing. Mark a clean edge.
- Use a thickness gauge to mark the required thickness along all edges of the part contour. Plan up to this risk. Check with a straightedge.
- Repeat the operation for the width.
- Now mark up the length and actual connections. Mark from the front side and a clean edge.
Lumber marking
Be careful when marking lumber. Make sufficient allowances for kerf width, planing thickness and joining.
All readings are taken from the front side and the clean edge, on which put the appropriate marks. In frame and cabinet designs, these marks should face inward to improve manufacturing accuracy. For ease of sorting and assembly, number the parts as they are manufactured on the front side so that, for example, it indicates that side 1 is connected to end 1.
When marking identical parts, carefully align them and make markings on all workpieces at once. This will ensure that the markup is identical. When marking profile elements, keep in mind that there can be “right” and “left” parts.
Butt joints
These are the simplest of joinery and carpentry joints. They can be included in all three categories of compounds.
Assembly
The butt joint can be reinforced with nails hammered at an angle. Drive the nails in randomly.
Trim the ends of the two pieces evenly and join them. Secure with nails or screws. Before this, glue can be applied to the parts to enhance fixation. Butt joints in frame structures can be reinforced with a steel plate or a corrugated key on the outside, or with a wooden block fixed on the inside.
Nail / dowel connections
Wooden dowels - today they are increasingly called dowels - can be used to strengthen the connection. These plug-in round spikes increase shear (shear) strength and, with adhesive, hold the assembly in place more securely. Dowel connections can be used as frame connections (furniture), drawer connections (cabinets) or for riveting/splicing (panels).
Assembling the dowel joint
1. Carefully cut out all the components to exactly the right dimensions. Mark the position of the crossbar on the face and clean edge of the upright.
2. Mark the center lines for the dowels at the end of the crossbar. The distance from each end must be at least half the thickness of the material. A wide bar may require more than two dowels.
Mark the center lines for the pins on the end of the crossbar and transfer them to the rack using the square.
3. Lay the upright and bar face up. On the square, transfer the center lines to the rack. Number and label all connections if there are more than one pair of uprights and crossbars.
4. Transfer this marking to the clean edge of the post and the ends of the crossbar.
5. From the front side with a thickness gauge, draw a risk in the center of the material, crossing the marking lines. This will mark the centers of the holes for the dowels.
With a thickness gauge, draw a center line, crossing the marking lines, which will show the centers of the dowel holes.
6. Using a power drill with a twist drill or a hand drill with a spade bit, drill holes in all parts. The drill must have a center point and cutters. The hole across the fibers should be about 2.5 times the diameter of the dowel, and the hole at the end should be about 3 times the depth. For each hole, make an allowance of 2 mm, at this distance the dowel should not reach the bottom.
7. Remove excess fibers from the top of the holes with a countersink. This will also make it easier to install the dowel and create space for the adhesive to secure the connection.
Nagels
The pin should have a longitudinal groove (now standard pins are made with longitudinal ribs), through which excess glue will be removed when assembling the joint. If the dowel does not have a groove, then cut it flat on one side, which will give the same result. The ends should be chamfered to facilitate assembly and prevent damage to the hole by the dowel. And here, if the dowels do not have a chamfer, make it with a file or grind the edges of their ends.
Use of pins for marking dowels
Mark and drill the crossbars. Insert special dowel pins into the pin holes. Align the crossbar with the markings of the rack and squeeze the parts together. The tips of the teats will make marks on the rack. Drill holes through them. Alternatively, you can make a template out of a block of wood, drill holes in it, fix the template to the part and drill holes for the dowels through the holes in it.
Using a jig for a dowel connection
The metal jig for dowel connections greatly facilitates the marking and drilling of holes for dowels. In box joints, the jig can be used at the ends, but it will not work on the face of wide panels.
conductor for nail joints
1. Mark center lines on the front of the material where the dowel holes are to be. Select a suitable drill guide bushing and insert it into the jig.
2. Align the alignment marks on the side of the jig and secure the slide bearing of the guide bush.
3. Install the jig on the part. Align the center notch with the center line of the dowel hole. Tighten.
4. Install the drilling depth gauge on the drill at the desired location.
Rallying
To get a wider wood detail using dowels, you can connect two parts of the same thickness along the edge. Place two boards with the wide sides together, line up the ends exactly, and clamp the pair in a vise. On a clean edge, draw perpendicular lines indicating the center lines of each dowel. In the middle of the edge of each board, with a thickness gauge, make risks across each previously marked center line. The intersection points will be the centers of the dowel holes.
The pin connection is neat and strong.
Flange / mortise connections
A notch, tie-in or groove connection is called a corner or middle connection, when the end of one part is attached to the layer and another part. It is based on a butt joint with an end cut made in the face. It is used in frame (house frames) or box (cabinets) connections.
Types of mortise / mortise connections
The main types of butt joints are the dark/semi-dark T-joint (often this term is replaced by the term "flush/semi-flush"), which looks like a butt joint, but is stronger, a quarter corner (corner joint) and a dark/semi-dark corner joint. The corner cut into the rebate and the corner cut into the rebate with darkness / semi-darkness are made in the same way, but the rebate is made deeper - two-thirds of the material is selected.
Making a cut
1. Mark a groove on the face of the material. The distance between the two lines is equal to the thickness of the second part. Continue the lines on both edges.
2. Use a thickness gauge to mark the depth of the groove between the marking lines on the edges. The depth is usually made from one quarter to one third of the thickness of the part. Mark the waste part of the material.
3. C-clamp the workpiece securely. Saw through the shoulders on the waste side of the marking lines to the desired depth. If the groove is wide, make additional cuts in the waste to make it easier to remove the material with a chisel.
Saw close to the marking line on the return side, making intermediate cuts with a wide groove.
4. Working with a chisel on both sides, remove excess material and check the flatness of the bottom. To level the bottom, you can use a primer.
With a chisel, remove the waste, working from both sides, and level the bottom of the groove.
5. Check the fit, if the piece is too tight it may need to be trimmed. Check for perpendicularity.
6. The notch connection can be strengthened by one of the following methods or a combination of them:
- gluing and clamping until the adhesive sets;
- screwing with screws through the face of the outer part;
- nailing at an angle through the face of the outer part;
- nailing obliquely through the corner.
The notch connection is strong enough
Tongue and groove connections
This is a combination of a quarter cut and a rebate cut. It is used in the manufacture of furniture and the installation of slopes of window openings.
Making a connection
1. Make the ends perpendicular to the longitudinal axes of both parts. On one part, mark the shoulder by measuring the thickness of the material from the end. Continue marking on both edges and front side.
2. Mark the second shoulder from the end, it should be at a distance of one third of the thickness of the material. Continue on both edges.
3. Use a thickness gauge to mark the depth of the groove (one third of the thickness of the material) on the edges between the shoulder lines.
4. With a hacksaw with a butt, saw through the shoulders to the risks of the thicknesser. Remove waste with a chisel and check for evenness.
5. Using a thickness gauge with the same setting, mark a line on the back and on the edges of the second part.
Adviсe:
- Tongue and groove type joints can be easily made with a router and an appropriate guide, either for the groove only or for both the groove and rebate. See p. 35.
- If the comb is too tight in the groove, trim the front (smooth) side of the comb or sand with sandpaper.
6. From the front side with a thickness gauge, make markings on the edges towards the end and on the end itself. Saw along the lines of the thickness gauge with a hacksaw with a butt. Do not cut too deep as this will weaken the connection.
7. Working with a chisel from the end, remove the waste. Check fit and adjust if necessary.
Half tree connections
Half-timber connections refer to frame connections, which are used to connect parts in layers or along an edge. The connection is made by taking the same amount of material from each part so that they are joined flush with each other.
Types of joins in half-tree
There are six main types of connections in the half-tree: transverse, angular, dark, angular on the mustache, dovetail and splicing.
Making a half-tree gusset
1. Align the ends of both parts. On the top side of one of the parts, draw a line perpendicular to the edges, stepping back from the end to the width of the second part. Repeat on the underside of the second piece.
2. Set the thicknesser at half the thickness of the parts and draw a line on the ends and edges of both parts. Mark the waste on the top side of one and the bottom side of the other part.
3. Clamp the part in a vise at an angle of 45° (face vertically). Carefully cut along the grain close to the thicknesser line on the back side until the saw is diagonal. Flip the piece over and continue sawing gently, gradually raising the saw handle until the saw lines up with the shoulder line on both edges.
4. Remove the part from the vise and place it on the face. Press it firmly against the hutch and clamp it with a clamp.
5. Saw through the shoulder to the previous cut and remove the waste. Align all irregularities in the sample with a chisel. Check the accuracy of the cut.
6. Repeat the process on the second piece.
7. Check the fit of the parts and, if necessary, level with a chisel. The connection must be rectangular, flush, without gaps and backlashes.
8. The connection can be strengthened with nails, screws, glue.
Corner joints on the mustache
Corner joints on the mustache are made using the bevel of the ends and hide the end grain, and also aesthetically correspond more to the angular rotation of the decorative overlay.
Types of corner connections on the mustache
To perform a bevel of the ends in a corner joint, the angle at which the parts meet is divided in half. In a traditional joint, this angle is 90°, so each end is cut at 45°, but the angle can be either obtuse or sharp. In uneven corner joints, parts with different widths are connected to the mustache.
Making a corner connection
1. Mark the length of the parts, keeping in mind that it should be measured on the long side, as the bevel will reduce the length inside the corner.
2. Having decided on the length, mark the line at 45° - on the edge or on the face, depending on where the bevel will be cut.
3. With a combination square, transfer the markup to all sides of the part.
4. When hand cutting, use a miter box and a backed hacksaw or hand miter saw. Press the part firmly against the back of the miter box - if it moves, the bevel will turn out uneven and the joint will not fit well. If you are sawing freehand, be careful not to deviate from the marking lines on all sides of the part. A miter saw, if you have one, will make a very neat bevel.
5. Place the two pieces together and check the fit. You can correct it by trimming the surface of the bevel with a planer. Firmly fix the part and work with a sharp planer, setting a small overhang of the knife.
6. The connection should be knocked down with nails through both parts. To do this, first lay the parts on the face and drive nails into the outer side of the bevel so that their tips slightly show out of the bevels.
Start nails in both parts so that the tips protrude slightly from the surface of the bevel.
7. Apply glue and squeeze the joint tightly so that one part protrudes slightly - overlaps the other. First, drive nails into the protruding part. Under hammer blows when driving nails, the part will move slightly. Surfaces must be level. Nail the other side of the connection and sink the nail heads. Check squareness.
Drive the nails into the protruding piece first, and the impact of the hammer will move the joint into position.
8. If there is a small gap due to unevenness, smooth the connection on both sides with a round screwdriver rod. This will move the fibers, which will close the gap. If the gap is too large, then you will either have to redo the connection, or close the gap with putty.
9. To reinforce the corner joint on the mustache, you can glue a wooden block inside the corner if it is not visible. If appearance is important, then the connection can be made on a plug-in spike or secured with veneer dowels. Pins or lamellas (standard flat studs) can be used inside the flat joints.
Splicing on a mustache and connection with cutting
Splicing on a mustache connects the ends of parts located on the same straight line, and a connection with a cut is used when it is necessary to connect two profile parts at an angle to each other.
Mustache splicing
When splicing with a mustache, the parts are connected by the same bevels at the ends in such a way that the same thickness of the parts remains unchanged.
Cutting connection
Connection with cutting (cutting, fitting) is used when it is necessary to connect two parts with a profile in the corner, for example, two skirting boards or cornices. If the part moves during its fastening, then the gap will be less noticeable than with a corner joint.
1. Fix the first skirting board in place. Move the second plinth close to it, located along the wall.
Fasten the first skirting board in place and press the second skirting board against it, aligning it with the wall.
2. Swipe along the profiled surface of the fixed plinth with a small wooden block with a pencil pressed against it. The pencil will leave a marking line on the plinth to be marked.
With a bar with a pencil pressed against it, attached with a tip to the second plinth, draw along the relief of the first plinth, and the pencil will mark the line of the cut.
3. Cut along the marking line. Check fit and adjust if necessary.
Complex profiles
Lay the first plinth in place and, placing the second plinth in the miter box, make a bevel on it. The line formed by the profile side and the bevel will show the desired shape. Cut along this line with a jigsaw.
Eyelet connections
Eyelet connections are used when it is required to join intersecting parts located "on the edge", either in a corner or in the middle (for example, the corner of a window frame or where a table leg meets a crossbar).
Eyelet Types
The most common types of eye connections are angle and tee (T-shaped). For strength, the connection must be glued, but you can strengthen it with a dowel.
Making an eyelet connection
1. Make a marking in the same way as for, but divide the material thickness by three to determine one third. Mark the waste on both parts. On one part, you will need to choose the middle. This groove is called an eyelet. On the second part, both side parts of the material are removed, and the remaining middle part is called a spike.
2. Saw along the fibers to the line of the shoulders along the marking lines on the side of the waste. Cut the shoulders with a hacksaw with a butt, and you get a spike.
3. Working on both sides, select the material from the eyelet with a chisel/grooving chisel or jigsaw.
4. Check the fit and fine-tune with a chisel if necessary. Apply adhesive to the joint surfaces. Check squareness. Use a C-clamp to clamp the joint while the adhesive cures.
Spike-to-socket connection
Spike-to-socket connections, or just spike connections, are used when two parts are connected at an angle or at an intersection. It is probably the strongest of all frame joints in carpentry and is used in the manufacture of doors, window frames and furniture.
Types of spike-to-socket connections
The two main types of stud joints are the usual stud-to-socket connection and the stepped stud-to-socket connection (semi-dark). The spike and socket are approximately two-thirds of the width of the material. The expansion of the nest is made on one side of the groove (semi-darkness), and a spike step is inserted into it from its corresponding side. The semi-darkness helps to prevent the thorn from turning out of the socket.
Standard spike-to-socket connection
1. Determine the position of the connection on both parts and mark on all sides of the material. The markup shows the width of the intersecting part. The spike will be at the end of the crossbar, and the socket will go through the post. The spike should have a small allowance in length for further stripping of the connection.
2. Pick up a chisel as close as possible in size to a third of the thickness of the material. Set the thickness gauge to the size of the chisel and mark the nest in the middle of the rack between the previously marked marking lines. Work from the front. If desired, you can set the thickness solution to a third of the thickness of the material and work with it on both sides.
3. In the same way, mark the spike on the butt and both sides to mark the shoulders on the crossbar.
4. Clamp a piece of wood secondary support in a vise high enough to attach the edge-on stand to it. Fasten the post to the support by placing the clamp next to the marking of the nest.
5. Cut out the nest with a chisel, making an inward allowance of about 3 mm from each of its ends so as not to damage the edges when sampling waste. Hold the chisel straight and parallel
its edges are the plane of the rack. Make the first cut strictly vertically, placing the sharpening bevel towards the middle of the socket. Repeat from the other end.
6. Make a few intermediate cuts, holding the chisel at a slight angle and bevel down. Select the waste by using the chisel as a lever. Going deeper by 5 mm, make more cuts and select a waste. Continue until about half the thickness. Flip the part over and work the same way on the other side.
7. After removing the main part of the waste, clean the nest and cut off the allowance left earlier to the marking lines on each side.
8. Cut the spike along the fibers, leading a hacksaw with a butt along the marking line from the side of the waste, and cut out the shoulders.
9. Check fit and adjust if necessary. The shoulders of the cleat must fit snugly against the post, and the joint must be perpendicular and free from play.
10. Wedges can be inserted on both sides of the spike to secure. A gap for this is made in the nest. Working with a chisel from the outside of the nest, widen about two thirds of the depth with a 1:8 slope. Wedges are made with the same bias.
11. Apply glue and press firmly. Check squareness. Apply glue to the wedges and drive them into place. Saw off the tenon allowance and remove excess glue.
Other spike connections
Stud joints for window frames and doors are somewhat different from half-dark stud joints, although the technique is the same. Inside there is a fold and / or an overlay for glass or a panel (panel). When making a connection with a spike into a socket on a part with a seam, make the plane of the spike in line with the edge of the seam. One of the shoulders of the crossbar is made longer (to the depth of the fold), and the second is shorter so as not to block the fold.
Studded joints for parts with overlays have a cut-off shoulder to match the profile of the overlay. Alternatively, you can remove the trim from the edge of the socket and make a bevel or cut to match the counterpart.
Other types of spike-to-socket connections:
- Side spike - in the manufacture of doors.
- A hidden beveled spike in semi-darkness (with a beveled step) - to hide the spike.
- Spike in the dark (steps of the stud on its two sides) - for relatively wide details, such as the lower trim (bar) of the door.
All these connections can be through, or they can be deaf, when the end of the spike is not visible from the back of the rack. They can be reinforced with wedges or dowels.
Rallying
Wide, high-quality wood is becoming increasingly difficult to find and very expensive. In addition, such wide boards are subject to very large shrinkage deformations, which makes it difficult to work with them. To connect narrow boards along the edge into wide panels for worktops or workbench covers, rallying is used.
Preparation
Before starting the actual rallying, you must do the following:
- If possible, select radial sawn boards. They are less susceptible to shrinkage than tangential sawn timber. If boards of tangential sawing are used, then lay their sound side alternately in one and the other side.
- Try not to bundle materials with different ways sawing into one panel.
- In no case do not rally the boards from different breeds wood if not dried properly. They will shrink and crack.
- If possible, arrange the boards with the fibers in one direction.
- Be sure to cut the material to size before stapling.
- Use only good quality glue.
- If the wood will be polished, adjust the texture or color.
Rallying for a smooth fugue
1. Lay all boards face up. To facilitate subsequent assembly, mark the edges with a continuous pencil line drawn at an angle along the joints.
2. Plan straight edges and check the fit to the corresponding adjacent boards. Align the ends or pencil lines each time.
3. Make sure that there are no gaps and that the entire surface is flat. If you squeeze the gap with a clamp or putty it, the connection will subsequently crack.
4. When planing short pieces, clamp the two right sides together in a vise and plan both edges at the same time. It is not necessary to maintain the squareness of the edges, since when docking they will mutually compensate for their possible inclination.
5. Prepare as for a butt joint and apply adhesive. Squeeze with lapping to connect the two surfaces, squeezing out excess glue and helping the surfaces to “stick” to each other.
Other payment methods
Other fusion joints with different amplifications are prepared in the same way. These include:
- with pins (dowels);
- in a groove and a comb;
- in a quarter.
Bonding and clamping
Gluing and fixing glued parts is an important part of woodworking, without which many products will lose strength.
Adhesives
The adhesive reinforces the connection, holding the parts together so that they cannot be easily pulled apart. Be sure to wear protective gloves when handling adhesives and follow the safety instructions on the packaging. Clean the product of excess glue before it sets, as it can dull the planer knife and clog the abrasive of the skin.
PVA (polyvinyl acetate)
PVA glue is a universal glue for wood. When still wet, it can be wiped off with a cloth dampened with water. It perfectly sticks together loose surfaces, does not require long-term fixation for setting and sets in about an hour. PVA gives a fairly strong bond and sticks to almost any porous surface. Gives a permanent bond, but is not heat and moisture resistant. Apply with a brush, or for large areas dilute with water and apply with a paint roller. Since PVA glue has a water base, it shrinks when setting.
contact adhesive
Contact adhesive sticks together immediately after application and connection of parts. Apply it to both surfaces and when the glue is dry to the touch, join them. It is used for laminate (laminate) or veneer to chipboard. Fixing is not required. Cleaned with solvent. Contact adhesive is flammable. Work with it in a well ventilated area to reduce the concentration of fumes. Not recommended for outdoor use, as it is not moisture and heat resistant.
Epoxy adhesive
Epoxy is the strongest adhesive used in woodworking and the most expensive. It is a two-component resin-based adhesive that does not shrink on setting and softens when heated and does not creep under load. Water-resistant and bonds almost all materials, both porous and smooth, with the exception of thermoplastics, such as polyvinyl chloride (PVC) or plexiglass (organic glass). Suitable for outdoor work. In the uncured form, it can be removed with a solvent.
hot glue
Hot melt adhesive bonds almost everything, including many plastics. Usually sold in the form of glue sticks that are inserted into a special electric glue gun for gluing. Apply glue, join surfaces and squeeze for 30 seconds. Fixing is not required. Cleaned with solvents.
Clips for fixation
Clamps come in a variety of designs and sizes, most of which are called clamps, but usually only a couple of varieties are needed. Be sure to place a piece of wood waste between the clamp and the product to avoid denting from applied pressure.
Gluing and fixing technique
Before gluing, be sure to assemble the product “dry” - without glue. Lock if necessary to check connections and dimensions. If everything is fine, disassemble the product, placing the parts in a convenient order. Mark the areas to be glued and prepare the clamps with the jaws/stops set apart to the desired distance.
Frame assembly
Spread the adhesive evenly with a brush on all surfaces to be glued and quickly assemble the product. Remove excess adhesive and secure assembly with clips. Compress the connections with even pressure. The clamps must be perpendicular and parallel to the surfaces of the product.
Position the clamps as close as possible to the connection. Check the parallelism of the crossbars and align if necessary. Measure the diagonals - if they are the same, then the rectangularity of the product is maintained. If not, then a slight but sharp blow to one end of the rack can even out the shape. Adjust clamps if necessary.
If the frame does not lie flat on a flat surface, use a mallet to tap the protruding sections through a piece of wood as a spacer. If that doesn't work, you may need to loosen the clamps or clamp the wood block across the frame.
Whether you are using wooden beams in the interior of the house, making a roof, perhaps building a terrace, you will need information - how the connection of wooden beams is made.
If earlier connections were made using spikes, then this old-fashioned method is gradually becoming a thing of the past, perhaps professionals still use it, but most likely in the near future they will begin to use more modern approaches.
Indeed, in our time, metal connectors allow you to quickly and reliably connect wooden beams. Unlike screwing, which is also only suitable for certain types of connections, such as diagonal braces. Today, wooden beam connectors are available for almost any type of connection.
The connectors are made from sheet steel and are pre-drilled. Smaller holes of 3.5 or 4.5mm are great for galvanized V-nails or comb nails. Some fittings also have larger holes with a diameter of 11 or 13.5 mm. They are used for hexagon head screws.
Below we will explain which fitting is suitable for connecting wooden beams and where.
1. T-joints for wooden beams
If you want to connect a beam to a transversely standing beam or, conversely, to connect a vertically standing beam to a horizontal one, you can make such a connection in several ways:
Straight connectors are 96 to 180 mm long (shown on the left) and are fastened with nails or screws.
There are even large straight connectors with a length of up to 400 mm or even up to 1250 mm - which allows you to attach to the beam at a great distance.
T-connectors, also called cross connectors, are suitable for 3-beam T-connections (2 cross beams are stacked side by side on the same post). Typically, these types of connections are used in the construction of canopies or terraces.
Such fasteners are primarily used when it is necessary to additionally stabilize rectangular beam joints. They are mounted at a 135° angle, for mounting at a different angle, an adjustable angle connector is used.
Alternatively, you can use universal connectors (multifunction connectors) with cut-out thigh ends. These connectors have a predetermined bending point so that they can be adapted to any desired angle. Thus, these beam connectors can be used in a wide variety of ways.
Rafter connections are used primarily for roof structures. Here, particularly strong beam connections are needed, as they are often subjected to strong winds.
Such strong connections are achieved with rafter connectors, which are available in six standard sizes. Such products are made in two types - right and left - so that the beam can be fixed on both sides.
Beam shoes are used when connecting a beam to a main beam. These connections are, in particular, the most common when arranging the interior of a room using beams.
This is a particularly strong connection that is used not only to connect a beam to a beam, but also a beam to concrete or brick, metal.
Such connectors are available in different versions: for mounting outside - type A, for mounting inside - type B. The second type allows you to make a more inconspicuous connection, but has a lower torsional rigidity than the first type.
The connection of a beam with a beam that does not correspond to standard dimensions can be realized using a two-section connector - Vario (type C).
5. Corner connectors for wooden beams
Corner connectors or corner sheets are primarily suitable for rectangular wooden joints, which will not be subjected to a large load. Therefore, they are often used in the manufacture of furniture and interior decoration.
Corner connectors are available in various sizes and designs, eg as a corner with perforated plate or slotted holes. Thus, they can be very versatile.
For greater stability, special heavy-duty connectors should be used.
Cross connectors are used, for example, in the construction of a pergola. To secure this kind of beam connection, connectors are available in several variants.
For perpendicular beam connections, connectors of the first type are very well suited (see figure). For angled cross connections, fork connectors can be used. A few more difficult option, but also possible, the use of connectors with two corners (item 5) for large loads.
When the main construction of houses - the construction of capital walls - is almost completed, you need to think about organizing floors, as well as interior and exterior decoration of a private house. Often, by this time, the main material resources of the site owners have been exhausted or are coming to an end. And sometimes it also happens that there is a lot of building material that would be good to use in construction. Then splicing floor beams can be a real salvation.
Beams are most often wooden bars rectangular section.
This means that in order to obtain one full-fledged beam, it is necessary to connect several pieces of the same section. Of course, this connection must be strong so that the resulting element can be used to implement the floors of private houses. Of course, building a house is a difficult long-term job. Some owners who cannot afford the construction of solid walls use frame wall construction options. What does it mean? Frame walls are built from thick load-bearing beams, both wooden and metal. They are fastened along the edges, as well as in places where the ceilings will be mounted. Frame walls definitely need to be filled. For this, as a rule, bulk materials or mineral wool are used.
What are overlays really?
Overlappings are of several types; For example, according to their location, they are divided into:
Before installing a wooden beam, it must be treated with an antiseptic solution.
- basement - they are usually located between the first floor and the basement of a private house;
- interfloor - these types of floors are located between floors;
- attic - they separate the residential floors from the attic.
In addition, floors can be divided according to the type of building materials from which they are made: beam or slab. Any floors, regardless of what they are and what materials they are made of, must provide thermal insulation, as well as sound and waterproofing. They can and should have increased strength, rigidity and fire safety. In addition, if the floors are wooden, they must be protected from rotting or mold. Decide on the type of floors that will be made in frame house, it is necessary long before construction, since the structures of beam or slab floors are completely different from each other.
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Basic requirements for floors
1. Of course, strength comes first.
Overlappings not only have to withstand their own weight, they also need to carry certain loads. And if the supports for the floors are frame walls, it matters a lot.
So, according to all the rules, any organized in residential buildings are required to withstand a total, but uniform load of about 200 kg / m² over the entire area; in practice, floors are usually built that are ready for higher loads. But less durable. Whether to reinforce the ceilings or not - it depends on what exactly will be in the room - a piano, a wardrobe, exercise equipment, etc.
When installing the ceiling, a sufficient degree of its sound insulation should be provided, the value of which is established by the norms or special recommendations for the design of buildings for one purpose or another.
2.Rigidity. In addition to the fact that the floor must withstand loads, it should not sag under them. If the floors sag, sooner or later they may undergo deformation, which will lead to destruction.
3. Heat and sound insulation. Mounted ceilings should also provide protection for the premises from the penetration of both airborne and impact noise from the rooms below. To do this, when organizing the overlap, a special mineral or any other insulation is used, which ensures the repayment of noise of any kind, and also retains heat in the room. standard size the insulation layer is 150 mm. When constructing such structures, various tools are also used. This:
- chainsaw;
- square;
- axe;
- hammer;
- electric drill;
- construction knife;
- chisel.
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Beam ceilings. Peculiarities
Wooden flooring is made of wooden beams of coniferous and hardwood.
Used beams for floors can be from different material: wood, metal, reinforced concrete. The design when using any of the above building materials is the same. in most cases, they are made with the help of load-bearing beams, the floor itself, the obligatory inter-beam filling and the necessary finishing layer of the ceiling. Sound and heat insulation can be provided with flooring, the so-called reel. The overlap resembles a kind of "sandwich", where all the layers must be present in the required size in order to get the desired result. Basically, beam ceilings, both interfloor, and basement and attic, are very similar to each other. They separate the living quarters of the house from the non-residential ones. Even their installation is carried out in the same way, with the exception of some nuances.
They should be mounted somewhat differently, since they have rooms on both sides, and not utility space. Wooden ones should be laid, as a rule, parallel to each other along the short side of the span. If the beams are not close to each other, the distance between them should be the same. When installing beam floors First of all, you need to fix the beams. Depending on which walls are implemented during the construction of houses - frame or capital - special gaps are left to fix the beams.
Table of the ratio of the width of the span and the width of the laying of beams.
- If the walls of the houses are capital and made of wood, then it is not necessary to prepare “nests” for the beams in advance - it will be enough to cut out suitable gaps for laying the floors during the installation of the beam ceilings. However, frame walls need specially prepared "nests".
- If wooden beams are used for floors, then it is necessary to pre-treat the ends of the beams to prevent them from rotting or premature destruction.
- For the width of the span, you need to take the appropriate section of the beams: the greater the width, the thicker the beam (see Table 21). If the span width is large enough, and the timber right size no, you can splice existing beams to achieve the desired thickness. This, of course, can lead to an overall lack of structural strength.
- To ensure rigidity, the resulting composite beam must be securely fixed at the joints. It is advisable to use such building elements at random - that is, so that the joints in these beams are not opposite each other. Thus, the pressure on the places where the beams are spliced is minimized and additional strength is achieved due to this.
So that the beams do not bend under the weight of the floor, they must be laid at a certain distance.
In addition, when organizing floors, you can use not only wooden beams. For this, logs are also suitable. desired diameter. Of course, they need to be trimmed from all sides. It will undoubtedly be cheaper, too, because lumber is worth much more than roundwood on the construction market. However, you can not use "fresh" logs. In order to use them at, you need to withstand the round wood for at least six months - a year in a dry place, otherwise the overlap will “lead” and this will cause the deformation of the whole house.
After laying a wooden beam or hewn logs, it is necessary to make a rolling floor. To do this, special cranial bars with a section of 5x5 cm are attached to the beams with the help of nails, and the selected roll boards are already placed on them; often craftsmen make it so that the lower part of the beam used for overlapping is equal to the reel. This contributes to further trouble-free finishing of the ceiling.
When laying the roll, it is not necessary to use full-fledged wooden planks- the "croaker" will fit quite well. After rolling comes the heat insulator. It can be completely different - from mineral wool to sawdust. Just like with beams, the reel must dry out. In addition, before laying the insulation, you need to roll up with paper. If it is decided to use sawdust or other bulk materials, then their amount should not exceed three-quarters of the height of the beam.
After laying the insulation on top of the beams, roofing felt or roofing material is laid, and only then - logs. However, in most cases, the logs are not laid if the floor beams are next to each other. If the beams are located far from each other, then the logs are necessary to create a continuous floor. When installing the basement and attic floors elements such as insulation and rolling may not be used. For backfilling, it would be logical to fill up with gravel and cover with roofing material.
Connections of wooden elements have the task of connecting mating Construction Materials, for example edged beams, so that they do not move relative to each other. According to the position and direction of the connected wooden elements, longitudinal joints and corner joints, as well as joints on branches and crosshairs, are distinguished. Spatial sheet steel connectors and pre-drilled steel sheet escutcheons often replace carpentry connections.
Connections that must transmit forces of a certain magnitude and direction, such as compressive forces, are also called joints of connected wooden elements like rods, for example, compressed rods. Compressed rods connected at an acute angle can be connected at notches. Other connections of wooden structures are arranged at the expense of joints of wooden elements using connecting means.
According to the type of connecting means, such connections are called nail or bolt, dowel or dowel connections. In the construction of wood, glued building structures are also used. Since they have particular advantages, the use of glued timber structures is of increasing importance.
Longitudinal connections
There are longitudinal connections on the supports and longitudinal connections in the span. Above the supports, perpendicular trunnions are used, a joint “in the paw” and a partially trunnion joint “in the paw” (Fig. 1). To reinforce these joints, building brackets made of flat or round steel can be driven in from above or from the side. Often, wooden elements are joined head-on and fixed only with building brackets. If, however, large tensile forces act at the joint, for example, at the girders on the roof rafters, then both elements are joined head-on on the support and connected by side plates made of boards or perforated strips of steel protected from corrosion.
Rice. 1. Longitudinal connections
Runs can also be made in the form cantilever-suspended(Gerber runs) or hinged girders. They have a joint located in a place determined by the calculation, not far from the support, in which the bending moments are equal to zero and where there are no bending forces (Fig. 2). There, the runs are connected with a straight or oblique overlay. The incoming purlin is held in place by a screw bolt, also called a pivot bolt. The swivel bolt with washers must bear the load from the suspended purlin.
Rice. 2. Longitudinal joints of Gerber girders
Gerber purlins with a seam lying on top are impractical, since there is a danger that the purlins at the edge of the seam will come off. With a suspended joint, having screwed up, there is no danger of separation.
To connect the Gerber purlins, spatial elements made of steel sheet are also used, which are also called Gerber connecting elements. They are attached with nails along the front butted ends of the runs (see Fig. 2).
Corner connections
Corner joints are necessary when two logs or beams in a corner are joined at a right or approximately right angle in the same plane. The most commonly used types of joints are cut-out trunnions, a smooth angular foot and a compressed foot (Fig. 3). With the help of cut-out trunnions and smooth corner legs, the ends of thresholds, girders and rafter legs lying on supports or protruding cantilevered are connected. Nails or screw bolts can be used to secure the joints. The compressed paw has planes obliquely entering each other. It is particularly suitable for connecting loaded, fully supported thresholds.
Rice. 3. Corner joints
Branches
When branching, a beam suitable at a right or oblique angle in most cases is superficially joined to another beam. In normal cases, a joint on the trunnions is used, and in secondary structures, a “paw” joint is also used. In addition, beams made of timber can be joined using metal spatial connecting elements. In trunnion joints, the thickness of the trunnion is approximately one third of the thickness of the timber. The trunnions have a length in most cases from 4 to 5 cm. The groove for the trunnion is made 1 cm deeper so that the compression force is transmitted not through the section of the trunnion, but through a large area of the remaining section of the bars.
When arranging trunnions, normal trunnions are distinguished, passing through the entire width of the beam, and protruding(hemp) pins, which are used for connections at the ends of the bars (Fig. 4). If the bars in the connection do not fit at right angles to each other, for example, at the corner struts, then the trunnion at the strut must be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).
Rice. 4. Pin connections
When installing trunnions in wooden beams and girders, the trunnion must bear the entire load. It is more advantageous to make such connections using beam shoes from corrosion-protected steel (Fig. 9). These shoes are fixed with special nails in such a way as to prevent them from buckling and turning relative to the joint. In addition, the cross section of the beam is not weakened by the trunnion holes.
Cross connections
Wooden beams can intersect in the same plane or with offset planes and be overhead or support. Bars intersecting in the same plane can intersect "IN THE LAPU" if the weakening of the section does not play any role (Fig. 5). It is advisable to tie the intersecting overhead thresholds on the support beams with round dowels (pins) made of hard wood or steel 10 to 12 cm long (Fig. 6).
Rice. 5. Connection "in the paw"
Rice. 6. Connection with round dowels (pins)
The beams joining on the side receive good support on the pole if their connection is made “In the groove” (Fig. 7). To do this, the intersection planes of both elements are cut to a depth of 1.5 to 2.0 cm. This results in an immovable connection, which is fixed with a screw bolt.
Rice. 7. Groove connection
When joining inclined and horizontal bars, as is usually the case when joining rafter legs with girders - thresholds, in rafter leg a cut is made corresponding to the slope, which is called sidebar(Fig. 8).
Rice. 8. Insert rafter leg
The depth of the tie-in in the rafter legs with a normal section height of 16 to 20 cm is from 2.5 to 3.5 cm. One nail is used for fastening, penetrating the threshold for a length of at least 12 cm, or a special anchor for attaching the rafters to the girders.
Rice. 9. Steel shoe connection
cuts
When cutting, a compressed rod entering at an acute angle is connected to another beam using one or more force-transmitting planes on its front side. According to the number and position of the force-transmitting planes, a frontal cut, a cut with a tooth, and a double front cut with a tooth are distinguished.
At frontal cutting(also called a frontal stop), the receiving beam has a wedge-shaped cutout that matches the shape of the end of the compressed rod (Fig. 10). The frontal plane must pass at an angle dividing the obtuse outer corner notches in half. The fastening bolt must also have the same direction, guaranteeing the joint from lateral displacement. To mark the cut, parallels are drawn at the same distance from the sides of the corner, which must be divided in half. The connecting line between the point of their intersection and the vertex of an obtuse angle will be the bisector of this angle (see Fig. 10). The position of the fastening bolt is obtained if the distance between the bisector and the end of the notch is divided into three parts parallel to the bisector (see Fig. 10).
Rice. 10. Frontal cutting
Under the action of a compressive force, the wood lying in front of the frontal part of the compressed rod works on slice(see fig. 10). Since the permissible stress on the cut of wood along the fibers is relatively small (0.9 MN / m 2), the plane of the wood in front of the cut edge (cut plane) must be large enough. Since, in addition, cracking due to shrinkage should be taken into account, with rare exceptions, the length of the cut plane should not be less than 20 cm.
At reverse or notched cut the cutting plane is cut at a right angle to the lower side of the compressed rod (Fig. 11). Due to the fact that due to an eccentric connection in a notched slot there may be a risk of splitting the compressed rod, it is necessary that the free end of the notch does not fit tightly against the support rod and a seam is provided between them.
Rice. 11. Serrated notch
double cut consists, as a rule, of a frontal cut in combination with a toothed cut (Fig. 12). The direction of the cutting planes is similar to that used for each of the cuttings of this combination. However, the notched cut in this case must be at least 1 cm deeper so that its cut plane is below the cut plane of the frontal cut. The fastening bolt should run parallel to the front of the notch approximately midway between the bisector and the top of the acute joint angle.
Rice. 12. Double notch
Cutting depth t v is limited according to DIN 1052. The decisive factors for this are the contact angle (a) and the height h of the cut rod (Table 1).
Pin and bolt connections
In the case of pin and bolt connections, wooden beams or boards that are in contact with the sides are connected by cylindrical connecting elements, such as rod dowels, bolts with countersunk heads and nuts, ordinary bolts with nuts. These rod dowels and bolts should prevent the wooden elements from moving in the connection plane, also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. Dowels and bolts at the same time work on bending. In the connected wooden elements, all efforts are concentrated on inner surface holes for dowels or bolts.
The number of rod dowels and bolts installed at the junction depends on the magnitude of the transmitted force. In this case, as a rule, at least two such elements should be installed (Fig. 13).
Rice. 13. Connection with rod dowels
In one connection, many shear planes can be located next to each other. According to the number of cut planes that are connected by the same connecting elements, single-cut, double-cut and multi-cut dowel and bolted connections are distinguished (Fig. 14). According to DIN 1052, single shear load-bearing connections with dowel pins must have at least four dowel pins.
Rice. 14. Bolted connections
For bolted connections, mainly bolts with nuts made of steel with a normalized diameter of 12, 16, 20 and 24 mm are used. In order to prevent the head and nut of the bolt from cutting into the tree, strong steel washers should be placed under them. The minimum dimensions of these washers are given for various bolt diameters in DIN 1052 (Table 2).
In order to prevent splitting of the wooden elements to be connected by rod dowels and bolts, these connecting means must have installed minimum distances between themselves, as well as from the loaded and unloaded ends. The minimum distances depend on the direction of the force, on the direction of the wood fibers and on the diameter of the dowel or bolt db and do (fig. 15 and 16). For load-bearing bolts with nuts, greater distances must be maintained between themselves and from the loaded end than in the case of rod dowels and bolts with hidden heads. On the other hand, rod dowels or bolts with hidden heads close to each other in the direction of the wood fibers should be spaced apart from the cut line so that the joints do not crack (see Fig. 15).
Rice. 15. Minimum distances in case of rod dowels and hidden head bolts
Rice. 16. Minimum distances in case of bearing bolts
Holes for pins and bolts are pre-drilled perpendicular to the cutting plane. For this, electric drills with a bed with parallel movement are used. For pins when drilling holes in wood, as well as when drilling holes in wood and metal connecting elements, the diameter of the hole must correspond to the diameter of the pin.
Also, the bolt holes should match the diameter of the bolts well. Do not increase the diameter of the hole in comparison with the diameter of the bolt by more than 1 mm. With bolted connections, it is bad when the bolt sits freely in the hole. It is also bad if, due to the shrinkage of the wood, the clamp of the bolt in the hole gradually weakens. In this case, a play appears in the shear plane, which leads to even greater pressure of the bolt shaft on the boundary planes of the hole walls (Fig. 17). Due to the flexibility associated with this, bolted connections cannot be used indefinitely. For simple buildings, such as sheds and sheds, as well as scaffolding, they can, however, be used. In any case, in the finished structure, the bolts must be tightened many times during operation.
Rice. 17. Backlash when bolted
Dowel connections
Dowels are fasteners made of hard wood or metal, which are used together with bolts to connect smoothly joined wooden elements (Fig. 18). They are positioned in such a way that they evenly act on the surface of the elements to be joined. In this case, the transmission of forces is carried out only through the dowels, while the bolts provide a clamping action in the connection so that the dowels cannot tip over. Laths made of flat or profiled steel are also attached to wooden elements using dowels. For this, one-sided dowels or flat steel dowels are used. Dowels are various forms and types.
Rice. 18. Connecting wooden elements with dowels and bolts
When making dowel connections with pressed dowels, bolt holes are first drilled in the elements to be connected. After that, the wooden elements are separated again, and, if necessary, a groove for the main plate is cut. Depending on the construction technology, the dowel is completely or partially driven into the groove of one of the connected elements using a mallet. For the final clamping of an axially aligned connection, special clamping bolts with a large washer are used. Connections with many or large pressed-in dowels are clamped with a hydraulic press. For connections with a large number of dowels, as is the case when making corner joints in frames made of glued plank elements, it is more preferable to use round plug-in dowels, since with pressed dowels the pressing pressure may be too high (Fig. 19).
Rice. 19. Dowel connection in the corner of the frame
Each dowel, as a rule, should correspond to one bolt with nut, the diameter of which depends on the size of the dowel (Table 3). The size of the washer is the same as for bolted connections. Depending on the magnitude of the force acting on the connection, larger or smaller dowels can be used. The most common are diameters from 50 to 165 mm. In the drawings, the size of the dowels is indicated by symbols (Table 4).
| Table 3. Minimum dimensions in dowel connections | ||
| Outer diameter d d in mm | Bolt diameter d b in mm | Distance between dowels/distance from dowel to element end, e db, in mm |
| 50 | M12 | 120 |
| 65 | M16 | 140 |
| 85 | M20 | 170 |
| 95 | M24 | 200 |
| 115 | M24 | 230 |
| The values are valid for the family of round push-in dowels type D. | ||
| Table 4. Drawing symbols for special type dowels | |
| Symbol | Dowel size |
 |
from 40 to 55 mm |
 |
from 56 to 70 mm |
 |
from 71 to 85 mm |
 |
from 86 to 100 mm |
 |
Nominal dimensions > 100 mm |
At dowel placement it is necessary to adhere to certain distances of the dowels between themselves and from the edges of the wooden elements. These minimum distances according to DIN 1052, they depend on the type of dowel and its diameter (see table. 3).
Bolts with dowel nuts are almost always driven through the center of the dowel. Only with rectangular and flat steel dowels do they lie outside the plane of the dowel. When tightening the nuts on the bolts, the washers should cut about 1 mm into the wood. For dowel connections, the nuts on the bolts must be re-tightened a few months after installation so that their tightening effect remains even after the wood has dried. They talk about a connection with a constant transmission of force.
Bearing pin connections
Bearing dowel (nail) connections have the task of transmitting tensile and compressive forces. With the help of dowel joints, load-bearing parts can be fastened, for example, for freely supported trusses, as well as structures made of boards and beams. Nail joints can be made single-shear, double-shear and multi-shear. In this case, the size of the nails should correspond to the thickness of the lumber and the depth of the drive. In addition, when arranging the nails, certain distances between them must be maintained. In load-bearing dowel joints, holes must be drilled in advance. The drilled hole should be slightly smaller in diameter than the diameter of the nail. Since the wood does not crack as much, the nails can be placed closer together in this way. In addition, the load-bearing capacity of the nail joint will increase and the thickness of the wood can be reduced.
Single shear dowel joints are used when compressed and stretched rods from boards or beams must be attached to the beams (Fig. 20). In this case, the nails pass through only one connecting seam. They are loaded there perpendicular to the shaft of the hole and can bend with too much force. Since shear forces also occur in the connecting seam in the body of the nail, this sectional plane is called the shear plane. In the case of paired joining of plank rods on the planes of the main beam, there are two single-cut dowel joints opposite each other.
Rice. 20. Single shear dowel connection
At double shear dowel joints the nails pass through three connected wooden elements (Fig. 21). Nails have two cut planes, since they are loaded in both connecting seams with the same directed force. Therefore, the bearing capacity of a double-shear loaded nail is twice that of a single-shear nail. In order for the double-cut dowel joints to not disperse, half of the nails are hammered on one side, and the other half on the other. Double-cut dowel joints are mainly used if freely supported trusses consist entirely or mainly of boards or beams.
Rice. 21. Double-cut dowel connection
Minimum timber thicknesses and minimum nailing depth
Since thin wooden elements easily split when hammering nails, boards for load-bearing rods, belts and planks must be at least 24 mm thick. When using nails from size 42/110, use even larger minimum thicknessesA(Fig. 22). They depend on the diameter of the nail. With pre-drilled nail joints, the minimum thicknesses of the wood can be less than with simple nailing, as there is less risk of cracking.
Rice. 22. Minimum thickness and depth of driving
The distance of the tip of the nail from the closest cutting plane is called the driving depth. s(see fig. 22). It depends on the diameter of the nail dn and has a different value for single-cut and double-cut nail connections. Single shear loaded nails must have a driving depth of at least 12d n. However, for certain special nails, due to the greater holding force due to the special profiling, a driving depth of 8d n is sufficient. For double shear connections, a driving depth of 8d n is also sufficient. With a shallower driving depth, the bearing capacity of the nails decreases. If the nails have a driving depth of less than half that required, then they cannot be taken into account for the transmission of forces.
Minimum spacing between nails
Fixing formwork, battens and fillets, as well as rafters, battens, etc. acceptable with less than four nails. However, in general, at least four nails are required for each seam or multi-shear nail joint intended for force transmission.
The uniform arrangement of these nails on the plane of the connection is made using nail lines(Fig. 23). In order for two nails located one behind the other not to sit on the same fiber, they are displaced relative to the point of intersection of mutually perpendicular nail lines by the thickness of the nail in both directions. In addition, minimum distances must be observed. They depend on whether the direction of the force is parallel or across the fibers. Further, it is necessary to monitor whether the ends of the rods or the edges of the wood are loaded by the force acting in the joint or not. Since there is a danger of cracking when the ends of the rods or edges are loaded, it is necessary to maintain large distances from the edges to the nails.
Rice. 23. Minimum distances between nails with a single shear connection
At single shear nail connection vertical or diagonal tensioned rod with nails with a diameter of d n ≤ 4.2 mm, the minimum distances shown in fig. 23. When using nails with a diameter of d n> 4.2 mm, these distances should be slightly increased. If the nail holes are pre-drilled, in most cases smaller distances are required.
At double-cut nail joints nails are arranged in ledges. Between the risks of a single-cut nail joint, additional risks are drawn with a minimum distance of 10d n (Fig. 24).
Rice. 24. Minimum distances between nails for double-cut joint
Nail connection device
When making nail joints, the nails must be driven vertically into the wood. In this case, the nail head should only be slightly pressed into the wood so that the wood fibers at the junction are not damaged. For the same reason, the protruding ends of the nails can only be bent in a special way. This should only happen perpendicular to the fibers. For drawing the location of the nails, as a rule, suitably drilled templates made of thin plywood or tin are used. In the case of plywood templates, holes are made of such a diameter that nail heads can pass through them. In the case of tin templates, the locations of the nails are marked with a brush and paint.
Nail connections with steel plates
Nail joints with steel plates can be divided into three types, namely, connections with embedded or externally laid plates with a thickness of at least 2 mm and connections with embedded plates with a thickness of less than 2 mm.
Overlays on the outside, as a rule, have in advance drilled holes(Fig. 25). They are superimposed over the connection of beams or boards to the butt and nailed with the appropriate number of wire or special nails. At embedded overlays with a thickness of at least 2 mm holes for nails must be drilled simultaneously in the wooden elements and in the overlays. In this case, the diameter of the holes must correspond to the diameter of the nail. Embedded linings less than 2 mm, of which there may be several at the junction, can be pierced with nails without pre-drilling (Fig. 26). Such connections may only be made with specially designed spline tools and only on the basis of special approval from the authorities.
Rice. 25. Connection with a perforated steel plate-lining
Rice. 26. Nail connection with embedded steel plates (Grame)
Connections with nail gussets
Nail gussets are used for the rational manufacture of wooden half-timbered trusses from single-row sections of wood (Fig. 27). To do this, cut to length wooden rods of the same thickness, impregnated and adjusted exactly to each other.
Rice. 27. Connection with a nail gusset
In this case, the moisture content of the wood should not exceed 20%, and the difference in thickness should not be more than 1 mm. In addition, the rods should not have any cuts and edges.
Nail gussets must be placed symmetrically on both sides and, using a suitable press, pressed into the wood so that the nails sit in the wood for their entire length. Hammering of nail gussets with a hammer or the like is unacceptable.
Fastening with the help of nail gussets creates a connection or joints that are strong in compression, tension and shear at nodal points without weakening the load-bearing section of the wood. For the transmission of forces, the working area of \u200b\u200bthe connection of the nail gusset is of primary importance (Fig. 28). It corresponds to the area of contact of the nail gusset with the wood, with the exception of the edge strip with a minimum width of 10 mm.
Rice. 28. Working area of the connection at the nail gusset
Trusses with connecting rods with gussets are industrially manufactured only by licensed enterprises, delivered ready-made to the construction site and mounted there.
The strength of the load-bearing roof systems must be given special attention, since the protection of the building from the weather depends on it. Mistakes made when attaching rafters to beams are fraught with big troubles, up to repairing the roof or even dismantling it and creating a new frame. Rafter beams are an indispensable part of the entire roof structure. They are made of wood and metal; a reinforced concrete rafter beam is also on sale.
When developing a roofing project and during its creation, many factors that create loads on truss structures are taken into account, among them:
- the weight of the coating and other elements of the roofing "pie";
- wind power;
- the greatest possible thickness of snow on the roof;
- the presence of equipment and other loads on the frame.
The main elements of the roof structure, which bear the most loads, include:
- rafter system or farm;
- composite beams.
Of course, the quality of the material from which the above materials are made is of great importance, but no less important is the strength and reliability of the connection of the roof elements to each other.
I-beams
I-beams are a structural material that is used for the construction of buildings according to frame technology, and also for the device of overlappings. They do not have the disadvantages inherent in wood, and due to the presence of an I-section, high strength characteristics are achieved. Docking of I-beams is carried out using a carpentry tool.
Methods for attaching rafters to walls
To date, the main options for installing rafters and attaching them to the walls of houses are as follows:
Fasteners for rafters
For Assembly roof structure use wooden elements and metal products. Wooden fasteners include: bars; triangles; pins, etc.
Metal fasteners are nails, bolts, steel angles, screws, studs, clamps, staples, special devices for rafters called skids or sliders, and much more.
WB beam fasteners are used when mounting load-bearing beams for wooden structures in the construction of wooden houses. Its advantage is that it does not require cutting into the beam, and fastening is carried out using nails, screws or anchor bolts.
Methods for attaching rafters to the Mauerlat
The most common way to attach the rafters in the lower part is their connection to the Mauerlat (read: ""). Despite its popularity, not every builder will be able to perform such work with high quality, and this cannot but affect the strength and reliability of the roof.
Before attaching the rafters to the Mauerlat beams, a special cut is made at the bottom of the rafter leg. It is impossible to install the rafters without this, because at the slightest load the flat edge of the beam will slide off the surface of the beam. As for the notch in the Mauerlat, whether to do it or not depends on the material of its manufacture.
In the case of using hardwood, experts recommend making an incision in the beam - it, together with the slot made in the rafter leg, will create a persistent lock. When the Mauerlat is made of coniferous wood, it is undesirable to make slots, as they will lead to a weakening of the structure. The condition of the roof in different weather conditions depends on the way in which the beams are fastened to the Mauerlat (read also: "").
Connecting a beam to a rafter leg
The roof of the house under the influence of loads on it tends to disperse to the sides and down. To prevent this, various design solutions are used that prevent the elements of the roof frame from shifting.
This is how the cutting of notches in the leg of the rafters was invented, which can be done using such connections as:
- tooth with one stop;
- tooth with a spike and an emphasis;
Fastening the rafters to the Mauerlat, look at the video:
A notch with one tooth is used when the roof has a large slope angle. This means that the rafters are attached to the floor beams at an angle of more than 35 degrees. A tooth with a spike is cut out in the leg, and a nest is created in the beam for the entrance of the spike. In this case, the recess depth cannot be more than 1/3 or 1/4 of the beam thickness, otherwise the element is weakened. The cut is made by stepping back from the edge of the beam 25 - 40 centimeters, then it will be possible to avoid the likelihood of chips. To prevent the connection from shifting to the side, a single tooth must be created together with the tenon.
A cut with a double tooth is performed for flat roofs, when the angle between the connection elements does not exceed 35 degrees, it is performed in one of the following ways:
- two spikes;
- emphasis without a spike;
- emphasis, supplemented with a spike;
- connection like a lock with two spikes and other options.
For both teeth, the incision depth is usually the same. But in some cases, the first tooth supplemented with a spike is cut into 1/3 of the thickness of the beam, and the second - by 1/2.
When creating roofs, there is such a method of arranging rafters when connecting rafter legs and wooden ceiling beams, but it is rarely used. In this case, a stop tooth is cut out in the leg so that one of its planes rests on the flat edge of the beam, and the other plane rests against a cut made with a depth of 1/3 of the beam thickness. For reliability, in addition to cutting, an additional connection is made using clamps, bolts, wire loops or strips of metal.
Joining rafters on a roof ridge
Currently, in the construction industry, when creating a rafter system, 3 methods of connecting rafters on a ridge are used:
- butt joint;
- installation on a ridge run;
- fastening with an overlap on the ridge run.
To understand which option is preferable, you need to understand how they are performed.
Butt joint . The upper part of the rafter leg is cut at an angle that is equal to the angle of inclination of the roof and abuts it against another rafter leg, which is also trimmed only in the opposite direction. Such work is performed according to a pre-made template. In some cases, in order to provide greater stress at the stop, trimming is performed during installation, while the cut is made through both bars, as a result of which the two planes fit snugly against each other. Then the rafters are connected to each other with long nails.
When this method is used, a metal or wooden lining is used for additional fastening - it is installed with bolts or nails are driven in at the junction.
Installation on a ridge run . This method is similar in many ways to the previous method. The difference lies in the installation of the ridge beam. This one is reliable, but it is not always possible to use it, since additional installation of support beams is required here and then it is not very convenient to use the attic.
This option allows you to work on the installation of each pair of rafter legs directly on site without preliminary work and the use of templates. The upper edge of the leg in this case rests on the ridge beam, and the lower edge on the Mauerlat.
Overlap fastening on the ridge run . The work is carried out similarly to the previous option, only the upper joint of the rafters is overlapped. They touch at the top not with their ends, but with their sides. Fasteners are bolts or studs.
Roof structure repair
A private house can be operated for more than a dozen years, and often a situation arises when it is necessary to repair the elements of the roof structure. The condition of the roof frame and roofing must be constantly monitored, since their destruction leads to great trouble. If defects are found, immediate action must be taken.
Problem: the end of the rafter leg began to rot based on Mauerlat. In such a situation, a log is placed on the floor of the attic, it must be supported by several beams (the installation of floor beams must be reliable). Braces are placed under the repaired rafter leg - it is necessary that they rest against the log. Between the extreme brace and the place of decay, the distance should exceed 20 centimeters. After the damaged segment is removed by sawing out, a pre-prepared liner is mounted in its place.
Problem: wood rot found in the middle of the rafter leg . In order to strengthen the truss structure, wooden linings from boards 50-60 millimeters thick are nailed on both sides of the damaged element. Nails for fastening are hammered along their edges into the undamaged part of the rafter.
Problem: Mauerlat damaged . When this is an insignificant area, experts advise installing struts with a rafter leg attached to them with brackets. The struts are mounted with support on the intact part of the Mauerlat. In the event that the area of \u200b\u200bdamage to the Mauerlat is significant, then an overlay of boards is nailed to the rafter leg, they, in turn, are attached to a new Mauerlat, which is installed slightly lower than the damaged one. An additional Mauerlat is mounted in the wall using pins, while performing in accordance with the project.
Problem: A crack has appeared in the rafter leg , resulting in a deflection of the roof. To carry out repairs, it is necessary to prepare 2 boards, one of them will become a squeeze rack, and the second will be a support for it. The base board is fixed perpendicularly load-bearing beams attic floors. The push-up stand is installed on a previously fixed support and brought under the deflection of the leg. Between the end of the squeezing rack and the support board, 2 wedges are driven in one towards the other. They continue to be hammered until the deflection is eliminated. In the place where the crack is located, two boards are placed, the length of which is not less than a meter greater than the size of the damaged area. They are fixed with bolts. Then the wedges are knocked out, the support board and the temporary stand are removed.
Problem: reinforcement of the truss system is required because new roofing material heavier than before. To do this, increase the main section of the rafters, increasing it with boards. What value needs to be increased (but not more than 5 centimeters) is determined using calculations (read also: ""). The gasket and the rafter are connected using nails.
