Connect wooden beams together. Basic requirements for splicing floor beams. Making an eyelet connection

Connections of wooden elements have the task of connecting mating building materials, such as edged beams, so that they do not move relative to each other. According to the position and direction of the wooden elements being connected, longitudinal connections and corner connections, as well as connections on branches and crosses, are distinguished. Spatial connecting elements made of sheet steel and plate steel plates with pre-drilled holes often replace carpenter's connections.

Connections that must transmit forces of a certain magnitude and direction, such as compressive forces, are also called joints of connected wooden elements as rods, for example compressed rods. Compressed rods connected at an acute angle can be connected using notches. Other connections of wooden structures are made by joining wooden elements using connecting means.

Based on the type of connecting means, such connections are called nail or bolt, dowel or dowel connections. In wood construction, glued building structures are also used. Because they have special advantages, the use of laminated timber structures is of increasing importance.

Longitudinal connections

There are longitudinal connections on supports and longitudinal connections in the span. Above the supports, perpendicular trunnions, a “toe-to-foot” joint and a partially “to-toe” trunnion joint are used (Fig. 1). To reinforce these joints, flat or round steel construction staples can be driven into the top or sides. Often wooden elements are butted head-on and secured only with construction staples. If, however, there are large tensile forces at the joint, for example, at purlins on the roof rafters, then both elements are butted head-on on a support and connected by side plates made of boards or perforated strips of corrosion-protected steel.

Rice. 1. Longitudinal connections

Purlins can also be made in the form cantilever-suspended(Gerber runs) or hinged purlins. Their joint is located in a place determined by 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 purlins are connected with a straight or oblique overlay. The incoming purlin is held in place by a screw bolt, also called a hinge bolt. The hinge bolt with washers must take the load from the suspended purlin.

Rice. 2. Longitudinal connections of Gerber purlins

Gerber purlins with a joint lying on top are impractical, since there is a danger that the purlins at the edge of the joint will come off. If the joint is suspended, if damaged, there is no danger of tearing off.

To connect 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 frontal butt ends of the purlins (see Fig. 2).

Corner connections

Corner joints are necessary when two logs or beams in a corner are joined at right or approximately right angles in the same plane. The most commonly used types of joints are cut-out trunnions, smooth corner foot and compressed foot (Fig. 3). With the help of cut-out trunnions and smooth corner paws, the ends of the thresholds, purlins and rafter legs lying on supports or protruding in a cantilever are connected. Nails or screws can be used to secure connections. The compressed paw has planes that enter each other obliquely. It is particularly suitable for connecting loaded, fully supported thresholds.

Rice. 3. Corner joints

Branches

When branching, a timber suitable at a right or oblique angle is in most cases superficially joined to another timber. In ordinary cases, a joint on axles is used, and in secondary structures a “claw” connection is also used. In addition, timber beams 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 beam. The axles have a length in most cases from 4 to 5 cm. The groove for the axle is made 1 cm deeper so that the compression force is transmitted not through the axle section, but through the large area of the remaining cross-section of the beams.

When arranging axles, a distinction is made between normal axles that extend across the entire width of the beam, and protruding(hemp) axles, which are used for connections at the ends of beams (Fig. 4). If the beams in the connection do not approach each other at right angles, for example, with corner struts, then the axle at the strut should be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).

Rice. 4. Trunnion connections

When installing axles in wooden beams and purlins, the axle must carry the entire load. It is more advantageous to carry out such connections using beam shoes made of corrosion-protected steel (Fig. 9). These shoes are secured 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 holes for the trunnions.

Cross connections

Wooden beams can intersect in one plane or with offset planes and be overhead or supporting. Beams intersecting in the same plane can intersect “IN THE PAW” if the weakening of the section does not play any role (Fig. 5). It is advisable to connect the intersecting overhead thresholds on the support beams with round dowels (pins) made of hard wood or steel with a length of 10 to 12 cm (Fig. 6).

Rice. 5. “claw” connection

Rice. 6. Connection using round keys (pins)

Side-joining beams receive good support on the pole if their connection is made “IN THE GROOT” (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 a non-shifting connection, which is secured with a screw bolt.

Rice. 7. “Groove” connection

When joining inclined and horizontal beams, as is usually the case when joining rafter legs with purlins - thresholds, a cutout is made in the rafter leg corresponding to the slope, which is called sidebar(Fig. 8).

Rice. 8. Inset of rafter leg

The depth of the cut in the rafter legs with a normal section height of 16 to 20 cm is from 2.5 to 3.5 cm. For fastening, use one nail that penetrates the threshold for a length of at least 12 cm, or a special anchor for attaching the rafters to the purlins.

Rice. 9. Connection with steel shoe

Cuttings

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. Based on the number and position of force-transmitting planes, a distinction is made between a frontal notch, a notch with a tooth, and a double frontal notch with a tooth.

At frontal cut(also called the frontal stop) the receiving beam has a wedge-shaped cutout corresponding in shape to the end of the compressed rod (Fig. 10). The frontal plane should pass at an angle dividing the obtuse outer corner of the notch in half. The fastening bolt must have the same direction, guaranteeing the joint against lateral displacement. To mark the notches, parallels are drawn at equal distances from the sides of the angle, 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 cut

Under the action of a compressive force, the wood lying in front of the frontal part of the compressed rod works to slice(see Fig. 10). Since the permissible stress for cutting wood along the fibers is relatively small (0.9 MN/m2), the plane of the wood in front of the cut edge (cut plane) must be quite large. Since, in addition, cracking due to shrinkage should be taken into account, then, with rare exceptions, the length of the cut plane should not be less than 20 cm.

At reverse or gear notch the notch plane is cut at a right angle to the underside of the compressed rod (Fig. 11). Due to the fact that due to the eccentric connection in a gear notch there may be a risk of splitting of the compressed rod, it is necessary that the free end of the notch does not fit tightly to the support rod and a seam is provided between them.

Rice. 11. Tooth cutting

Double cut consists, as a rule, of a frontal notch in combination with a gear notch (Fig. 12). The direction of the notch planes is the same as is customary for each of the notches of this combination. However, the serrated notch in this case must be at least 1 cm deeper so that its cut plane is lower than the cut plane of the frontal notch. The fastening bolt should run parallel to the frontal part of the notch approximately halfway between the bisector and the top of the acute joint angle.

Rice. 12. Double cut

Cutting depth t v is limited according to DIN 1052. The determining 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 touching their sides are connected by cylindrical connecting elements, such as dowel rods, bolts with recessed heads and nuts, and ordinary bolts and nuts. These rod dowels and bolts are designed to prevent the wood members from moving in the joint plane, also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. Dowels and bolts work in bending. In connecting wooden elements, all efforts are concentrated on the inner surface of the 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 using rod dowels

In a single joint, many shear planes may be located adjacent to each other. Based on the number of cut planes that are connected by identical connecting elements, single-cut, double-cut and multi-cut dowel and bolt connections are distinguished (Fig. 14). According to DIN 1052, single-cut load-bearing connections using dowel rods must have at least four dowel rods.

Rice. 14. Bolted connections

For bolted connections, bolts and nuts made of steel with standardized diameters of 12, 16, 20 and 24 mm are mainly used. To prevent the head and nut of the bolt from cutting into the wood, 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).

To prevent splintering of the connected wooden elements by the core dowels and bolts, these connecting means must be 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 grain and on the diameter of the dowel rod or bolt db and do (Fig. 15 and 16). For load-bearing bolts and nuts, greater distances must be maintained between each other and from the loaded end than for rod dowels and bolts with hidden heads. But dowel rods or bolts with hidden heads located close to each other in the direction of the wood fibers should be spaced apart relative to the cut line so that the joints do not crack (see Fig. 15).

Rice. 15. Minimum distances for dowel rods and hidden head bolts

Rice. 16. Minimum distances in case of load-bearing bolts

Holes for pins and bolts are pre-drilled perpendicular to the cutting plane. For this purpose, electric drills with a frame with parallel movement are used. For pins, when drilling holes in wood, as well as when simultaneously drilling holes in wood and metal connecting elements, the diameter of the hole must correspond to the diameter of the pin.

Also, the holes for the bolts should be well suited to the diameter of the bolts. The diameter of the hole cannot be increased compared to the diameter of the bolt by more than 1 mm. With bolted connections, it is bad when the bolt sits loosely in the hole. It is also bad if, due to shrinkage of the wood, the clamp of the bolt in the hole gradually weakens. In this case, a backlash appears in the cut plane, which leads to even greater pressure from the bolt rod on the boundary planes of the hole walls (Fig. 17). Due to the associated flexibility, 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 in bolted connections

Dowel connections

Dowels are fasteners made of solid wood or metal that are used together with bolts to connect smoothly joined wooden elements (Fig. 18). They are positioned in such a way that they act evenly on the surface of the elements being connected. In this case, the transmission of forces occurs only through the dowels, while the bolts provide a clamping effect in the connection so that the dowels cannot tip over. Slats made of flat or profile steel are also attached to wooden elements using dowels. To do this, use single-sided dowels or flat steel dowels. Dowels come in various shapes and types.

Rice. 18. Connecting wooden elements using dowels and bolts

When making dowel connections with pressed-in dowels, holes for the bolts are first drilled in the elements being connected. After this, the wooden elements are again separated, and a groove is cut, if necessary, for the main plate. Depending on the construction technology, the dowel is completely or partially driven into the groove of one of the elements being connected using a mallet. For final clamping of a precisely aligned connection, special clamping bolts with a large washer are used. Connections with many or large pressed-in dowels are clamped using a hydraulic press. When making connections with a large number of dowels, as is the case when making corner connections in frames made of laminated board elements, it is more preferable to use round plug-in dowels, since with pressed-in dowels the press-in pressure may be too high (Fig. 19).

Rice. 19. Dowel connection in the corner of the frame

Each dowel, as a rule, must correspond to one bolt and 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 diameters are from 50 to 165 mm. In the drawings, the size of the dowels is indicated by symbols (Table 4).

Table 3. Minimum dimensions for dowel connections
Outer diameter d d in mm	Bolt diameter d b in mm	Distance between dowels/distance from dowel to the end of the element, 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 press-in dowels type D.

Table 4. Drawing symbols for special types of 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 placement of dowels You should maintain certain distances between the dowels and from the edges of the wooden elements. These minimum distances according to DIN 1052 depend on the type of dowel and its diameter (see Table 3).

The bolts and nuts of dowel joints are almost always passed 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 approximately 1mm into the wood. For dowel joints, the nuts on the bolts must be tightened again several months after installation so that their tightening effect remains even after the wood shrinks. They talk about a connection with constant force transmission.

Load-bearing dowel connections

Load-bearing dowel (nail) connections have the task of transmitting tensile and compressive forces. With the help of dowel connections, load-bearing parts can be fastened, for example, for simply supported trusses, as well as structures made of boards and beams. Dowel connections can be made single-cut, double-cut and multi-cut. In this case, the size of the nails must correspond to the thickness of the lumber and the depth of driving. In addition, when placing nails, certain distances between them must be maintained. In load-bearing dowel connections, holes should be drilled in advance. The drilled hole should be slightly smaller in diameter than the diameter of the nail. Since this does not cause the wood to crack as much, the nails can be placed closer together in this way. In addition, the load-bearing capacity of the nail joint will be increased, and the thickness of the wood can be reduced.

Single shear dowel connections 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 hole shaft and can bend if too much force is applied. Since shear forces also arise in the connecting seam in the body of the nail, this section plane is called the shear plane. In the case of paired connection of plank rods on the planes of the main beam, there are two single-cut dowel connections opposite each other.

Rice. 20. Single-cut dowel connection

At double shear dowel connections the nails pass through the three wooden elements being connected (Fig. 21). The nails have two cutting planes, since they are loaded with the same directional force in both connecting seams. Therefore, the load-bearing capacity of a double-shear loaded nail is twice that of a single-shear nail. To prevent double-cut dowel joints from coming apart, half the nails are driven in on one side and the other half on the other. Double-shear dowel connections are mainly used if simply supported trusses consist entirely or predominantly of boards or beams.

Rice. 21. Double-cut dowel connection

Minimum thicknesses of wooden elements and minimum nailing depth

Since thin wooden elements easily split when hammering nails, the 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 ones minimum thicknessA(Fig. 22). They depend on the diameter of the nail. With dowel joints with pre-drilled holes, the minimum thickness of wood will be less than with simple nailing, since there is less risk of cracking.

Rice. 22. Minimum thickness and driving depth

The distance of the nail tip 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 12dn. 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 8dn is also sufficient. With a shallower driving depth, the load-bearing capacity of the nails decreases. If nails have a driving depth of less than half the required, then they cannot be taken into account for the transmission of forces.

Minimum distances between nails

Fastening of formwork, slats and fillies, as well as rafters, lathing, etc. acceptable using less than four nails. However, in general, a minimum of four nails are required for each seam or multiple nail joint intended to transmit forces.

The uniform arrangement of these nails on the connection plane is done using nail marks(Fig. 23). To ensure that two nails located one behind the other do not sit on the same fiber, they are shifted relative to the point of intersection of mutually perpendicular nail marks by the thickness of the nail in both directions. In addition, minimum distances must be maintained. They depend on whether the direction of force is parallel or across the fibers. Next, it is necessary to monitor whether the ends of the rods or the edges of the wood will be loaded by the force acting in the connection 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 for a single-cut connection

At single shear nail connection vertical or diagonal stretched rod with nails with a diameter d n ≤ 4.2 mm, the minimum distances shown in Fig. 23. When using nails with a diameter d n > 4.2 mm, these distances should be increased slightly. If nail holes are pre-drilled, shorter distances are required in most cases.

At double shear nail connections the nails are arranged in ledges. Between the risks of a single-shear nail connection, additional risks are drawn with a minimum distance of 10d n (Fig. 24).

Rice. 24. Minimum distances between nails for a double-cut connection

Installation of nail connections

When making nail connections, 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 joint are not damaged. For the same reason, the protruding ends of the nails can only be bent in a special way. This should only occur perpendicular to the grain. To apply the location of nails, as a rule, appropriately drilled templates made of thin plywood or tin are used. In the case of plywood templates, the holes are made of such a diameter that the nail heads can pass through them. In the case of templates made of tin, the locations of the nails are marked with a brush and paint.

Nail connections with steel plates

Nail connections with steel plates can be divided into three types, namely connections with embedded or externally lying plates with a thickness of at least 2 mm and connections with embedded plates with a thickness of less than 2 mm.

Externally lying pads, as a rule, have pre-drilled holes (Fig. 25). They are placed over the joint of beams or boards at the end and nailed with the appropriate number of wire or special nails. At embedded overlays with a thickness of at least 2 mm nail holes must be drilled simultaneously in the wood members and in the trims. In this case, the diameter of the holes must correspond to the diameter of the nail. Embedded overlays with thickness less than 2 mm, of which there may be several at the joint, can be pierced with nails without pre-drilling (Fig. 26). Such connections can only be made using specially designed spline tools and only with special approval from the authorities.

Rice. 25. Connection using a perforated steel plate-plate

Rice. 26. Nail connection with embedded steel plates (Greim)

Connections using nail gussets

Nail gussets are used for the rational production of wooden half-timbered trusses from single-row sections of wood (Fig. 27). To do this, wooden rods of equal thickness are cut to length, impregnated and adjusted exactly to each other.

Rice. 27. Connection using a nail gusset

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 or edges.

The nail gussets must be positioned symmetrically on both sides and, using a suitable press, pressed into the wood so that the nails sit in the wood to their full length. Driving nail heads using a hammer or the like is not permitted.

Fastening with 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 main importance is the working area of the connection of the nail gusset (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 width of at least 10 mm.

Rice. 28. Working area of the connection at the nail gusset

Trusses with gusseted connections of rods are industrially manufactured only by licensed enterprises, delivered ready-made to the construction site and installed there.

Joints of beam elements

Features of factory, enlargement and installation joints. The need to make joints between the elements that make up the beam may arise, firstly, due to the insufficient length of sheets and angles rolled in factories compared to the length of the beam and, secondly, due to the fact that the total weight of the beam or overall dimensions it is not possible to transport or lift entire beams with the equipment available at the construction site.
In the first case, the joints of individual elements are arranged during the manufacture of the beam at the factory and are therefore called factory joints. In the second case, the joints of parts of the beams are made at enlarged installation sites, and if the carrying capacity of the installation equipment is insufficient, at the permanent location of the structure. The first of them are called enlarged joints, and the second - installation joints.
The position of the joints of individual elements made at the factory depends mainly on the length of these elements. The length of the wide sheets used for the wall, and the narrow ones that go to the belts, as well as the corners, are different, so the factory joints are arranged in different places on the beams, or, as they say, in bulk. Independent joining of individual elements during the manufacture of a beam does not cause any particular difficulties. Factory joints of sheets in the belts and walls are welded before the belt seams are applied, which ensures freedom of deformation when the joints cool, as well as ease of arrangement of the joints themselves and their subsequent processing, if required. In order to reduce the number of templates for the manufacture of individual elements, it is useful to place their joints symmetrically relative to the middle of the beam span. This creates greater repetition of elements.
Enlargement and assembly joints connect all longitudinal elements of the beam. The relative position of these elements at the time of making the joints is strictly fixed. Due to their large size and weight, rotation of the connected parts is difficult during enlarged assembly, and completely impossible during assembly. Therefore, when designing such joints, one should carefully consider the conditions of work and the availability of individual elements for welding or installing bolts (rivets).
In addition, for the convenience of transporting individual sections of beams and reducing the risk of damage to their elements, it is desirable that the latter do not form protruding parts (overhangs).
The fastening of each beam element at the joint must be designed for the force factors acting in this element (N, Q or M).
Joints in welded beams. When designing joints, it is necessary to take into account the order of welding of beam elements. This order should be such as to ensure the greatest freedom of deformation and movement of the individual elements being connected and thereby reduce the amount of shrinkage stresses. For this purpose, as noted above, factory welding of the belts and the wall is carried out separately, and then the belts are connected to the wall; in enlargement and assembly joints of beams, the waist seams do not reach the joint by approximately 50 cm (Fig. IV-18, b, c). It also shows the recommended sequence for constructing welds at the beam joint to reduce the harmful effects of shrinkage stresses.

In beams of variable section, joints of chord sheets are usually used to change their width or thickness. In a multi-sheet package, the joints of individual tapes should be spaced apart.
The most rational type and the only one acceptable in beams operating under dynamic loads is the joint of sheets without overlays (Fig. IV-18, a). Butt joints reinforced with overlays require more metal (base and weld metal), more time and labor, and the endurance limit of joints with overlays is lower than without overlays. Joints covered only with overlays have a particularly low endurance limit.
In the compressed belt of the beam, all butt seams are arranged at right angles to the longitudinal axis. If the quality of stretched butt welds can be checked by γ-ray transmission or other advanced control methods, then such seams can be made straight anywhere in the beam. Butt welds, if they are located in places with tensile stresses σ>0.85R, should be illuminated in the stretched belt and in the part of the wall adjacent to it at a length of about 1/10 of the wall height. If it is impossible to use increased control means, stretched joints are arranged straight in places with stresses σ≤0.85R or oblique with an angle σ=65° between the direction of the seam and the longitudinal axis of the element (ratio of legs 2.1:1).
If a straight butt weld of a wall has a calculated tensile stress of more than Rр св = 0.85R, but the stretched belt in this place does not have a joint or its welded joint is of equal strength to the belt, then the wall seam will work under conditions of constrained deformation. Therefore, in a limited area adjacent to such a belt, you can not be afraid of the harmful consequences of design overvoltages and leave the wall seam straight.
When manufacturing beams intended for static loads, in workshops that do not have equipment for precise cutting of sheets and preparing edges for joint seams, as well as when there are large gaps between the joined parts of beams during installation, it is permissible to cover the joints of wall sheets and chords only with overlays. The joint of the wall sheets is covered with two rectangular overlays (Fig. IV-18, d), welding them with corner seams. The thickness of the wall linings is usually the same as the wall thickness. In this case, two flat frontal seams (1:1.5), laid along the long sides of the linings, have a greater load-bearing capacity than the wall:

Therefore, there is no need to install flank seams. It is difficult to arrange flank seams if belts are welded to the wall. The width of the linings is set to about 10 times their thickness (to reduce the influence of shrinkage stresses and for a smoother deflection of power flows).
The strength of the fillet welds should be checked because the length of the overlays is less than the full height of the wall.
The belts are covered with overlays. One-sided linings cause a sharp deviation of power flows and deterioration in the performance of the belts. The thickness of the overlays is determined by the required height of the fillet welds; in this case, the cross-sectional area of the lining must be no less than the cross-sectional area of the sheet being overlapped. In places where one-sided pads are attached to the belt, the height of the waist seams should be slightly increased in order to reduce the adverse effect of eccentricity at the joint.
Calculation of fillet welds attaching linings to waist sheets is carried out either by the force acting in the sheet at the joint N=Fσ, or by the load-bearing capacity of the sheet [N]=FR:

where ΣFш is the calculated area of fillet welds located on one side of the joint.
Considering the presence of eccentricity in the joint with a one-sided overlay, it is useful to increase the calculated force by approximately 20%.
The seams attaching the linings to the wall are calculated using the bending moment Mst acting in the wall:

where ΣWш is the sum of the moments of resistance of fillet welds located on one side of the joint.
The magnitude of the bending moment Mst attributable to the beam wall is determined from the proportionality between the bending moments attributable to individual parts of the composite beam and the stiffness of these parts:

where Ist, Ip and Ib are the moments of inertia of the wall, chord and the entire beam relative to the neutral axis of the beam;
Mb is the bending moment acting on the beam at the joint.
The seams connecting the linings to the wall must also be checked for the effect of shear force acting at the joint. Due to the low rigidity of the beam chords compared to the wall, it is assumed (as a safety factor) that the entire transverse force is absorbed by the seams at the wall linings. Average shear stress in seams:

where ΣFш is the sum of the areas of fillet welds located on one side of the joint.
Although the maximum stresses from shear force do not coincide with the maximum stresses from bending moment, they do conditionally check the strength of the seams under the influence of both force factors:

Beam connections

Beams can be connected to each other in a variety of ways. The choice of connection method depends on the relative position of the beams, on the force factors and on the connection means used.
Intersecting beams can be located one above the other or at the same level. In addition, adjacent beams are sometimes located obliquely in relation to the main beams in a horizontal or vertical plane.
Beam connections that transmit only support pressures are called free (hinged). Connections that transmit both support pressures and support moments are called rigid (pinched).
When designing connections between main and secondary beams, it must be taken into account that in most cases the latter are used as connections that ensure the overall stability of the main beams.
The easiest way to fasten beams is when they are located on floors.
Oblique washers should be placed from the inside under the nuts of the bolts adjacent to the flanges of I-beams and channels to eliminate the bending of the bolts in the threaded part of them.
Places where heavily loaded auxiliary beams rest on composite beams must be reinforced with stiffeners tightly fitted to the upper chord to eliminate local overstresses of the chord joints and the wall. In such cases, rolled beams should be checked for compression of the wall under the fillet connecting it to the flange. In case of overvoltage, ribs must be installed.
Connections of beams at the same level and lowered are divided into fastenings that do not require precise cutting of auxiliary beams and require precise cutting of them. The latter are very labor-intensive and therefore undesirable.
Auxiliary beams located at the same level or lower can be conveniently attached to the transverse ribs of the main beam using bolts (Fig. IV-19, a). In this case, one or both flanges of the auxiliary beams and part of the wall have to be cut off. The vertical and horizontal parts of the cut are matched by a rounding with a radius of about 20 mm. This fastening does not require precise cutting of the auxiliary beams and is convenient for installation, just like fastening the beams using a table (Fig. IV-19, b), which takes on all the support pressure.

Bolts or welds along the wall are needed to keep the auxiliary beams from tipping over and the main beam from losing stability. In the latter respect, fastening the beams to the rib is more effective than to the table.
Fastenings of freely adjacent beams are designed for support pressure A, increased by 20-30%. This takes into account the presence of minor moments in the support fastenings. If the moments are large, their influence must be taken into account in the calculation.

An example of a rigid connection of beams at one level, ensuring the transfer of not only support pressures, but also support moments, is presented in Figure IV-20. Attaching the upper chord of the auxiliary beam to the plate (called a “fish”) and the lower chord to the table must be designed for force

where M0 is the support moment of the beam,
h" - height of the auxiliary beam.
The fastening of the horizontal table to the vertical is calculated on the resultant force N and support pressure A, if the wall of the auxiliary beam is not attached directly to the main beam (Fig. IV-20, right), and on part of the support pressure A1, if the wall is attached to the main beam (Fig. IV-20, left).
The share of support pressure - A1, transmitted through the table, and the share A2, transmitted directly from the wall to the corners, are determined under the assumption of direct proportionality between these forces and the areas of the seams securing the wall of the auxiliary beam and the console to the main beam.
The welds attaching the table to the main beam must be designed for the operating pressure A and the moment M=Ae-Nz, where e is the eccentricity of the application of force A; z is the distance from the force N to the center of gravity of the calculated welds.

An example of a rigid welded joint at a reduced level is shown in Figure IV-21. The fastening of double-walled beams is complicated by the fact that in their supporting sections there are support pressures and moments not only in the vertical plane, but also in the horizontal, as well as torques. An example of fastening a double-walled crane bridge beam to an end beam is shown in Figure IV-22. Both walls 1 of the crane beam are welded to the wall of the end beam using vertical plates 2. In the places where the walls of the crane beam adjoin the end beam, diaphragms 4 must be placed between the walls 3 of the latter. The belts of the crane beam in the assembly are replaced or covered with nodal gussets 5, expanding at an angle of 45 °. In high-speed cranes, the free edges of the nodal gussets 5 are rounded and ensure a smooth connection of the gusset edges to the chords of the connected beams. The crane beam belts can be butt welded with continuous penetration directly to the end beam belts. To stiffen the unit in this case, inserts in the shape of an isosceles triangle with a leg length and no less than the width of the wider belt of the connected beams are placed between the chords of both beams.

When calculating such connections, it is conventionally assumed that the vertical seams between the walls and the linings (w-1 and w-2) act on the vertical support pressures AB of the adjacent beam. Horizontal seams between chords and nodal inserts (w-3) act on vertical and horizontal moments and horizontal support pressures of the adjacent beam.
When calculating such connections, it is conventionally assumed that the vertical seams (w-1 and w-2) between the walls (1 and 3) and the linings (2) work to transmit the supporting vertical pressure AB of the adjacent beam. In fact, these seams also absorb some fractions of vertical and horizontal bending moments. This circumstance is taken into account by increasing the support pressure by 20-30%. When calculating the seams, it is also necessary to take into account the influence of the design moment M" = Авbн, where bн is the width of the vertical lining (the distance between the seams w-1 and w-2).

It is also conventionally believed that the horizontal seams (w-3 and w-4) between the nodal gussets and the chords of the connected beams work on the horizontal support pressure Ag of the adjacent beam (without increasing by 20-30%) and on the bending moments acting in the vertical and horizontal (Mv and Mg) planes. The total edge stresses in the weld (w-3) can be approximately checked using the formula:

where Fshz is the area of one horizontal seam (w-3) between the nodal gusset and the belt of the adjacent beam;
Wshz - moment of resistance of the same seam;
hп is the distance between the centers of gravity of the chords of the adjacent beam.
An example of the graphic design of a welded single-wall beam is presented in Figure IV-23.

When the main construction of houses - the construction of main walls - is almost completed, you need to think about the organization of floors, as well as the interior and exterior decoration of a private house. Often by this point the main material resources of the land owners have already been exhausted or are coming to an end. And sometimes it happens that there is a lot of building material left that would be good to use in construction. Then splicing the floor beams can be a real salvation.

Beams are most often wooden beams of rectangular cross-section.

This means that 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 for the implementation of floors for private houses. Of course, building a house is a complex long-term job. Some owners who cannot afford the construction of permanent 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 attached along the edges, as well as in places where the ceilings will be mounted. Frame walls definitely need filling. For this, as a rule, bulk materials or mineral wool are used.

What are overlaps really?

There are several types of ceilings; 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;
attics - 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: beams or slabs. 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 molding. It is necessary to decide on the type of floors that will be made in a frame house long before construction, since the designs 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.

Floors not only must support their own weight, they also need to bear certain loads. And if the supports for the floors are frame walls, this is of great importance.

So, according to all the rules, any structures organized in residential buildings are required to withstand a total, but uniform load over the entire area of about 200 kg/m²; in practice, they usually build floors that are ready for higher loads. But less durable. Whether to reinforce the floors or not depends on what exactly will be in the room - a piano, a closet, exercise equipment, etc.

When installing the floor, a sufficient degree of sound insulation must be provided, the amount of which is established by standards or special recommendations for the design of buildings for a particular purpose.

2.Rigidity. In addition to the fact that the ceiling must withstand loads, it must not sag under them. If the floors sag, they may sooner or later undergo deformation, which will lead to destruction.
3.Heat and sound insulation. The installed ceilings must also protect the room from the penetration of both airborne and impact noise from the rooms below. To do this, when organizing the ceiling, a special mineral or any other insulation is used, which ensures the suppression of noise of any kind, and also retains heat in the room. The standard size of the insulation layer is 150 mm. When constructing such structures, various tools are used. This:

chainsaw;
square;
axe;
hammer;
electric drill;
construction knife;
chisel.

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Beam floors. Peculiarities

The wooden floor is made from wooden beams of coniferous and hardwood.

The floor beams used can be made of various materials: wood, metal, reinforced concrete. The design when using any of the above building materials is the same. in most cases, they are made using load-bearing beams, the floor itself, the mandatory inter-beam filling and the necessary finishing layer of the ceiling. Sound and heat insulation can be provided by flooring, the so-called roll-up. The overlap resembles a kind of “sandwich”, where all layers must be present in the required size in order to obtain the desired result. Basically, beam floors, both interfloor, basement and attic, are very similar to each other. They separate the residential areas of the house from the non-residential ones. Even their installation is carried out the same way, with the exception of some nuances.

They must be mounted slightly differently, since they have rooms on both sides, 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 located close to each other, the distance between them should be the same. When installing beamed interfloor floors, first of all you need to secure the beams. Depending on what kind of walls are used during the construction of houses - frame or solid - special gaps are left to secure the beams.

Table of the relationship between the span width and the width of the beams.

If the walls of the houses are solid and made of wood, then it is not necessary to prepare “sockets” for the beams in advance - it will be enough to cut out suitable gaps for laying the floors when installing the beam floors. However, frame walls require specially prepared “nests”.
If wooden beams are used for floors, it is necessary to pre-treat the ends of the beams to prevent them from rotting or premature destruction.
For the span width, you need to take the corresponding section of the beams: the larger the width, the thicker the beam (see Table 21). If the width of the span is large enough, and there is no timber of a suitable size, then the existing beams can be fused to achieve the required thickness. This, of course, can lead to overall structural instability.
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 due to this additional strength is achieved.

To prevent beams from bending under the weight of the floor, they must be placed at a certain distance.

In addition, when organizing floors, you can use not only wooden beams. Logs of the required diameter are also suitable for this. Of course, they need to be trimmed on all sides. This will undoubtedly be cheaper - after all, lumber on the construction market costs much more than round timber. However, you cannot use “fresh” logs. In order to use them, you need to keep the round timber for at least six months to a year in a dry place, otherwise the ceiling will “lead” and this will cause deformation of the entire house.

After laying wooden beams or hewn logs, it is necessary to make a rolling flooring. To do this, special cranial bars with a cross-section of 5x5 cm are attached to the beams using nails, and the selected knurling boards are placed on them; craftsmen often make sure that the lower part of the beam used for the ceiling is level with the roll. This contributes to further trouble-free finishing of the ceiling.

When laying the ramp, it is not necessary to use full-fledged wooden boards - a “slab” will do just fine. After the roll-up comes the heat insulation. It can be completely different - from mineral wool to sawdust. Just like with beams, the roll must dry out. In addition, before laying the insulation, you need to lay the roll with paper. If the decision is made to use sawdust or other bulk materials, then their quantity should not exceed three quarters of the height of the beam.

After laying the insulation, roofing felt or roofing felt is laid on top of the beams, and only then the logs. However, in most cases, joists are not laid if the floor beams are located next to each other. If the beams are located far from each other, then logs are necessary to create a continuous floor. When installing basement and attic floors, elements such as insulation and shingles may not be used. For backfilling, it would be logical to fill it with gravel and cover it with roofing felt.

All photos from the article

In this article we are going to find out how to calculate wooden floor beams. In addition, we will get acquainted with the general principles of constructing insulated floors and learn how their insulation is calculated.

Wooden flooring is a typical solution for a private home.

How everything works

Coniferous wood is the most popular material for the construction of interfloor and attic floors in a private house. The main reason is obvious - the low price compared to monolithic reinforced concrete or ready-made slabs.

In addition: a floor on wooden beams, unlike a slab floor, can be installed without the services of loading equipment, which also provides significant savings.
It differs favorably from monolithic in that it does not require the construction of formwork.

If necessary:

Ensure their sufficient load-bearing capacity under the calculated long-term loads;
Perform effective interfloor sound insulation;
If we are talking about a ceiling above an unheated basement or under an unused attic, organize sufficiently effective thermal insulation that meets the requirements of the climate zone in which you live.

The first problem is solved by selecting the optimal section and pitch of the beams. The maximum length of a wooden floor beam is usually limited to 6 meters - the length of kiln-drying timber supplied by manufacturers; for larger spans, intermediate load-bearing walls or support columns are constructed.

To solve the second and third problems, the space between the beams is filled with insulation - glass or mineral wool, expanded polystyrene, ecowool and other materials. Their choice is a topic for a separate study; We will not focus our attention on it.

A typical design of an insulated floor is as follows:

On the side surfaces of the beams in their lower part, cranial bars with a cross section of 40x40 mm are packed.

Boards are laid on them without fastening thickness from 25 mm.
A vapor barrier film is spread over the flooring. It covers both flooring boards and beams.
Insulation is placed between the beams.
The top is covered with waterproofing(most often this role is played by ordinary polyethylene with taped seams between the sheets).
The subfloor is laid over waterproofing- directly along the beams (if the floorboard is thick enough) or along the joists perpendicular to them. In the first case, a counter-lattice is placed between the beams and the flooring - a 20 mm thick lath, which leaves a gap under the flooring for ventilation.

Load capacity calculation

general information

We have already mentioned the maximum span: it is limited by the length of the supplied timber. However, the optimal span for wooden load-bearing structures is considered to be 2.5 - 4 meters. Among other things, a smaller span makes it possible to use timber of a smaller cross-section, which reduces the cost of the floor structure.

It is optimal to use timber with a rectangular cross-section as beams. Its height should be in a ratio of 1.4:1 to its width. In this case, we obtain maximum load-bearing capacity at, again, minimal costs.

However: real ones force us to deviate somewhat from the optimal proportion of sizes.

The beam must rest on the wall at least 12 centimeters in length from the edge.

The edge resting on the wall is waterproofed on all sides except the end. When sealing the ends with moisture-impermeable material, the ends will sooner or later rot due to lack of natural drying.

When calculating interfloor slabs, the calculated value of the full load (self-weight of the slab and operational load) of 400 kgf/m2 is usually used. However, for unused attics this value can be reduced.

Section tables

Let's start by selecting the cross-section of a rectangular beam for a load of 400 kgf/m2 at different values of the span and pitch between the beams.

When constructing an attic floor under an unused attic, the design load can be in the range of 150 - 350 kgf/m2. With a step between beams of one meter, their sections in centimeters should be as follows:

Another table contains the minimum diameters of round beams (rounded logs) at a load of 400 kgf/m2 and a step of 1 meter.

Splicing and strengthening

How to extend a wooden floor beam if the beam you purchased is shorter than the required span?

First and foremost: with any joining method, the resulting beam will have much less strength than a solid wood one. The ideal solution would be to build an additional load-bearing wall with a reduced span. As an option, retaining columns are installed under the splice areas.

How to lengthen a wooden floor beam if the load on it is insignificant (for example, there is an unused attic upstairs)?

The most reliable way is to connect two beams without reducing the thickness of each of them. The elements are simply connected with steel pins with wide overlapping washers; You can further strengthen the connection by gluing it with casein, albumin glue or regular PVA.

Important: places of fusion when o
In the absence of retaining walls or columns, they are located staggered, with an offset from beam to beam. In this case, the load-bearing capacity of the floor will be maximum.

Another good solution is the construction of prefabricated beams from three wide boards of small thickness (25 - 50 mm). And in this case, the butt joints of the boards inside each beam and between adjacent beams are spaced apart; the boards are glued along their length and additionally tightened with pins.

How to strengthen wooden floor beams with increased demands on their load-bearing capacity (for example, when turning a cold attic into an attic)?

There are not many ways:

Construction of retaining columns or walls with a reduced span;
Hemming each beam with an additional board or timber along the entire length, from wall to wall.

In the latter case, it is useful to know one subtlety:

Hemming timber of the same section on the side doubles the load-bearing capacity of the beam.
Increasing the height of the beam by 2 times (filing the same beam from below or from above) will increase the load-bearing capacity by four times.

So how to strengthen wooden floor beams by adding additional boards or timber to them?

We place temporary timber supports in the middle of the span under every second beam, removing the deflection of the floor.
We reinforce beams free from columns with overlays made of timber or boards. The location and thickness of the lining is selected taking into account the design loads and the height of the room; fastening method - adhesive seam with additional fixation with studs with wide washers or galvanized plates.
We rearrange the supporting columns and repeat the operation with the remaining beams.

It is curious that the rigidity of beams can be significantly increased using ordinary plywood with a thickness of 18 - 22 millimeters. It is cut into strips with a width equal to the height of the beams, and after eliminating the deflection of the floor with retaining columns, it is glued to each beam on both sides, secured with nails or self-tapping screws in increments of 15 - 25 centimeters.

Of course, here too the spacing of the transverse seams is required - both on each individual beam and between adjacent beams.

Insulation

We have already given instructions for constructing an insulated floor; however, the calculation of the insulating layer depending on the material used and climatic conditions requires comment.

The main property of any insulation is its thermal conductivity. The lower it is, the better insulation is provided by a layer of fixed thickness.

For each region of the country, depending on the winter temperatures in it, Russian SNiP 02/23/2003 proposes its own standards for the thermal resistance of enclosing structures.

Thermal resistance consists of the resistance of each layer of the wall or ceiling; however, specifically for floors, the properties of flooring, vapor and waterproofing can be neglected, since their heat-insulating qualities are seriously inferior to those of any modern insulation.

The thickness of the insulation layer is calculated using the simplest formula: it is equal to the product of the calculated thermal resistance and the thermal conductivity coefficient of the selected thermal insulation material.

Important point: all values are given in SI units; Accordingly, we will get the result in meters.
To calculate the insulation layer in centimeters, simply multiply it by 100.

Obviously, only reference data is missing for the calculation. To save the reader from searching for them, we present these values here.

City	Normalized thermal resistance of the ceiling, (m2*C)/W
Arkhangelsk	4,6
Kaliningrad	3,58
Moscow, Penza, Saratov	4,15
Krasnodar	2,6
Astrakhan	3,6
Orenburg	4,49
Permian	5,08
Tyumen	4,6
Omsk	4,83
Ekaterinburg	4,38
Surgut	5,28
Krasnoyarsk	4,71
Chita	5,27
Khabarovsk	4,6
Vladivostok	4,03
Petropavlovsk-Kamchatsky	4,38
Magadan	5,5
Anadyr	6,39
Verkhoyansk	7,3

Let us clarify: actual thermal conductivity values may vary depending on the density of materials and atmospheric humidity.
The dependence in both cases is linear: an increase in density and humidity leads to an increase in thermal conductivity.

As an example, let’s do it with our own hands and calculate the insulation of the floor above a cold underground floor for a house built in the Astrakhan region.

Insulation - basalt wool.

The photo shows slab insulation based on basalt wool.

The normalized thermal resistance from the upper table is taken equal to 3.6 (m2*C)/W.
The thermal conductivity of basalt wool is 0.042 W/(m2*C).
The minimum required insulation thickness is therefore 3.6 * 0.042 = 0.1512 meters, or 15 centimeters.

Conclusion

We hope that we were able to answer all the reader’s questions. Additional information about the construction of floors using wooden beams can be obtained from the video in this article. Good luck!

The beam floor is a multi-element system that carries not only mechanical loads, but is also designed to serve as a heat-insulating and sound-absorbing layer between floors, basement and roof.

All elements of the beam structure are installed and connected in a certain way and form one whole. Today we will talk to you about what such floors can be, give some tips on their construction, and deal with other issues on the topic. Let's get started!

Features of wooden beam floors

All beam floors can be divided according to the type of material used. The most common and easiest to install are wooden elements. In addition to them, reinforced concrete and steel are also used, but this is already in the area of mass and industrial construction, so there is no need to describe them.

The popularity of the tree primarily depends on its prevalence in our country and its quite reasonable cost. It is also worth noting the ease of installation, in which builders do not need heavy lifting equipment.
Of course, wood will not last as long as metal, but with proper processing it will last a very long time. As they say, enough for our lifetime!

The environmental friendliness of the material can also be a disadvantage - various insects and microorganisms like to live in wood, but all this can be easily eliminated with proper treatment with antiseptics.
It is immediately worth noting that wood is a flammable material. To avoid this drawback, beams are impregnated with special fire retardant compounds, which impart fire-fighting properties to the wood for a certain period of time.

Interesting to know! The durability of wooden beam floors largely depends on the type of wood used. Let's take, for example, the former apartment buildings of St. Petersburg, which today are more than 200 years old. Among them there are even seven-story buildings, and everywhere wood was used as beams, which, even in the humid northern climate, continues to serve to this day.

The difference between those floors, of course, is the use of logs for beams, and not beams, but all the same, beams in private housing construction will serve for quite a long time.

Parameters of wooden beams

So, today, wooden beams are mainly used as beams - a log of a certain section sawn on four sides. The wood used is mainly coniferous, since the material is naturally “impregnated” with resins, which protects it well from moisture.

For small spans not exceeding 2 meters, it is allowed to use boards with a thickness of 25, 32 or 40 millimeters, installing them on edge.
If you need to strengthen the load-bearing elements, you can connect two boards, as shown in the photo above, using nails, screws or bolted connections.

Logs today are used only in the construction of log houses, and even then beams are often used there too.

The parameters of the beams directly depend on the width of the span they cover, as well as the step between them.
When calculating the project, the possible loads that will be exerted are also taken into account. Here is a table that will help you navigate the selection of the cross-section of load-bearing beam elements.

The information given in the table is obtained from GOST 24454-80.

Advice! The calculation of the pitch between the beams includes a potential payload of 200 kgf/m3, as well as the weight of the beams themselves, plus the mass of mineral wool insulation with a density of up to 100 kg/m3. If it is planned to insulate the floor with expanded clay, then the pitch between the beams should be reduced by 20% of the stated value.

The main feature of a wooden beam floor is that when installed on wide spans it can provide sufficient strength, however, due to the characteristics of the material, the floor cannot be rigid, that is, it still bends, especially with increasing load. This property is called floor instability.

How beams are laid out and embedded in the wall

So, the length of the beams is selected according to the opening to be blocked, which is not surprising. Moreover, if the room has a rectangular shape, its smaller side is selected. If it is square, then the direction does not matter.

Advice! It is worth remembering that beams can only rest on load-bearing walls, which are designed to withstand increasing loads - light half-brick partitions cannot be used for these purposes under any circumstances.

Depending on the size of the room, the layout of the beams can be done in different ways. If the spans are too large, you can break them into smaller sections using more massive beams.

The beams are embedded in brick walls, and at the points of connection with each other they are fixed using special steel fasteners or plywood overlays.

In order to wall up beams into the wall, it is necessary to prepare special niches for them during the laying process, which will correspond to the dimensions of the beams used.
In order for the connection to be sufficiently reliable and withstand all the necessary loads, the landing depth of the end of the beam must be at least 15 centimeters. This applies to any brick, stone or block wall.
In this case, the depth of the niche itself should be 20-30 millimeters greater to provide an air gap to the rear wall.
If the wall has a heat-insulating layer on the outside, then the inside of the niche need not be filled with anything.
If there is no such layer, then due to the remaining small thickness of the wall, the niche can turn into a cold bridge that will freeze when the outside air temperature drops. As a result, condensation will begin to form on the wooden beam, which, as you understand, is very bad and will lead to accelerated aging of the material. To prevent this from happening, the niche is filled with heat-insulating material, for example, polystyrene, which itself does not allow moisture to pass through and will perfectly protect the beam.

The diagram above shows how beams are installed in different types of walls.

Advice! The insulation placed inside does not need to be wrapped in plastic film, since condensation may form in a closed space, as a result of which the niche may freeze.

Before laying in a niche, the ends of the beams must be sawed off at an angle of 60-70 degrees.
The saw cuts and the entire immersed part are treated with an antiseptic composition.
You will also need to create a moisture-proof layer - the edge of the beam is wrapped with roofing felt or roofing felt (the second option is better). In this case, the end is left open to ensure air flow

If you wish, you can not wrap the edges, but this is less reliable. In this case, it is necessary to put pads under the beams - the same roofing felt, roofing felt or a piece of board soaked in an antiseptic to prevent the wood from coming into contact with the stone. If this is not done, the process of wood rotting will begin soon enough.
The most reliable way to do this would be to combine these two methods, that is, place the wrapped beam on a substrate, which, in principle, is shown in the previous diagram.

The gaps that remain around the beam must be sealed with polyurethane foam. Such a coating will reliably protect the wood from moisture that can get inside from the room, but at the same time the whole thing will be ventilated through microscopic pores.
The remaining space is filled with cement mortar.
If a backing made of boards treated with an antiseptic is placed not only at the bottom, but also on all sides of the niche, the beam will last even longer, almost like those found in the already mentioned ancient buildings. True, back then tar was used as an antiseptic, but modern impregnations are also perfect.

Advice! Also, ancient beams were additionally treated with soot - a natural antiseptic, which coped with the task no worse than modern compounds prepared by the chemical industry.

If you support the beams on an internal load-bearing wall, then all measures to insulate the element from moisture must also be taken.
When building a house, it is very important to remember that beams, in addition to their main load-bearing function, strengthen the walls of the building, which, as we know, are connected to each other only at the corners. Even in a two-story house, the height of the walls reaches 6-7 meters, so without the proper connection, unpredictable consequences can occur.
That is, the beams should not just lie in prepared niches, but be rigidly connected to the walls of the building. For this purpose, anchoring of these elements is used.

Anchoring is carried out using prepared T-shaped metal plates, one edge of which is nailed to the beam, and the remaining blades are embedded in the masonry.
Anchors can be placed on each beam, or through one - in both cases the bundle will be strong enough.

When connecting to wooden walls, special fasteners with perforations are used, through which everything is secured with self-tapping screws. In this case, the edges of the beams should also rest on the cut niches, as in the photo.

In some cases, hinged joining is also allowed, but then perimeter boards must be screwed to the walls.

If two beams are supported on an interior wall, then they must be connected to each other with steel strips, which are stuffed on both sides.

We should also talk about supporting floor beams on walls made of aerated concrete blocks. This material does not have a high density and is not able to fully support the weight of the floor and roof.

Therefore, a monolithic reinforced concrete belt is poured, which will greatly strengthen the structure and fix the beams themselves. It is also possible to lean on the belt itself - this will be even more reliable.
For this purpose, special “U”-shaped aerated concrete blocks are used, in which recesses are cut along the edges of the beams.
You can see a similar connection in the photo above.
Anchoring in this case is performed using metal plates that are connected to the armored belt itself.

Supporting beams on vertical elements

If we are talking about a frame structure, then the beams are often additionally supported by a system of free-standing supports, such as columns, pillars, racks.

If it is necessary to connect elements above a vertical support, then the joint should be located strictly above it.

If both elements are made of wood, then the joining is quite simple - nails are driven in at an angle and the whole thing is additionally fastened with staples.
The connection can also be made using wooden or plywood overlays installed on both sides. Fastening is performed perpendicularly using nails or self-tapping screws.
Having examined the diagram above, you can see that various metal connectors are also used, which can be purchased ready-made in the store. They are usually made of galvanized steel to prevent corrosion of the element.

Inter-beam filling of the floor

The filling between the beams is essentially a set of enclosing elements, each with its own purpose. Let's see what device options there are here.

This type of construction can only be used if the distance between the load-bearing beams does not exceed 60 centimeters. If this rule is neglected, the floor will be “unsteady”. The layout of such an overlap is shown in the following diagram.

Let's break this cake down layer by layer:

So, in this case, our floor beams become the basis for holding the sheathing, a subfloor will be laid on top of them, and inside there will be layers of vapor, heat and sound insulation - the last two, often in the form of one material.
Let's go from bottom to top. The lowest layer is the finishing material of the ceiling, which can be plastic, wooden lining, plasterboard, MDF, etc. The trim is installed last if you do not plan to lay the insulation directly on top of it. This solution is extremely unreliable, so we will skip its description.

To keep everything firmly in place, especially if a fairly heavy thermal insulator such as expanded clay is used, a wooden flooring (12) is mounted below, which will be held in place by cranial bars (10) wound parallel to the beams along their lower edge. For cranial bars, a rail with a cross section of 30*40 and higher is perfect. Everything is attached with self-tapping screws.

Next, a layer of vapor barrier is placed on top of the flooring, which will prevent debris from spilling down, plus it will protect the beams themselves and the insulation between them from the penetration of moisture from the air.
Next is a layer of thermal insulation - usually it is either foamed polystyrene or mineral wool, although there are a great many other options on the market. Moreover, mineral wool would be preferable, since it is not a flammable material and is not afraid of rodents.

Advice! Mineral wool greatly loses its thermal insulation properties when wet, so it is necessary to take care of its high-quality insulation.

The next layer is again film, but this time waterproofing. Water can seep out from above if something is spilled on the floor or the roof leaks. It is also recommended to use membrane films that do not interfere with gas exchange.
The distance from the film to the insulation is usually left at 50 millimeters to ensure air circulation, although sometimes this rule can be neglected

But what about sound insulation, since today’s popular insulation materials are not so effective in this regard? Of course, the weight of the same mineral wool per 1 square meter will be some 5-6 kilograms, and sound in such a loose environment will propagate practically without interference!

In this case, before laying the insulation, it is worth installing a separate layer of sound insulation, for example, installing a soundproofing panel, or pouring sand or clay, if we are talking about a very budget construction project. At the same time, do not forget that the load-bearing capacity of the floor must withstand increased loads.

It is also necessary to place a separating membrane film between the layers of sound and thermal insulation.

Sound insulation will not be complete if vibrations are transmitted through the beams themselves when walking on the floor of the upper floor. To eliminate this unpleasant effect, an elastic material, for example, the same roofing felt, is laid over the beams.

Next, a rough flooring is installed, which will serve as the basis for a finished floor covering, for example, laminate. For flooring, boards with a thickness of 32 millimeters are used - thinner is possible, but provided that the step between the beams is small and the floor will not sag.

Floors with joists

During the course of the article, we analyzed the table, from which it became clear that the cross-section of the beams and the step between them are interrelated quantities. The pattern here is directly proportional - the more powerful the bars, the greater the distance between them it is allowed to leave.

The approach with a large indentation is good for reducing labor costs in terms of arranging niches for beams, but the strength of the floor itself may suffer.
Logs help solve the problem - transverse boards or beams that are placed on an edge or laid flat. Lumber is taken with the following section - 50x75 or 50x100 millimeters.
The step between them is chosen to be acceptable for the future flooring. The end connection of the elements is performed above the logs. The fastening element in this case is a wooden, metal or plywood overlay.

The inter-beam filling of the floor will be the same as in the previous case, however, due to the increased thickness of the floor, you can add another layer of insulation to make the insulation more effective. You also need to remember that, unlike beams, logs are not embedded in the wall, but simply adjacent to them.

So, we have learned how a beam ceiling is constructed, which you can now easily build yourself, following the recommendations given in this article. The video in this article will help further clarify the issue - be sure to take a look. And now we say goodbye to you, see you soon!