Overlapping beams from wood provide not only the strength of the horizontal design. The overlap is intended to give stiffness to the entire building. It is for this reason that the choice of carrier elements and their installation is worth paying special attention.
Pros and disadvantage of wood overlap
To mount the overlap with their own hands it is necessary to prepare. The floor in the house should rely on a solid and rigid design. Before starting work, you will have to explore the requirements for elements, the features of their calculation and types of sections.
The following advantages of Wooden Overlap are available:
- attractive appearance, the ability to make a wooden floor without additional events;
- low weight, reduced load on walls and foundations, economy in construction;
- the ability to carry out repairs during operation;
- installation speed, performance without additional machines and mechanisms.
But it is also worth allocating disadvantages:
- flammable wood, the need for special impregnation with antipirens;
- less compared to reinforced concrete or metal elements;
- shrinkage and deformation with temperature and humidity drops;
- exposure to rotting, fungus and mold with high humidity, it is necessary to carry out the processing of antiseptics at the construction stage and periodically during the service life.
Woodble Requirements
Wooden beams overlap must comply with the following requirements:
- matching the size of the section of the load, span and the step, for this you need the calculation of the beams;
- good strength and rigidity;
- fire safety;
- the absence of serious wood defects and damage.
For work it is necessary to prepare high-quality material There are also certain requirements for the material from which the beams are made. It is recommended to choose wood coniferous rocks. It contains a lot of resin, so it is better resisting various microorganisms. The best materials are those trees that have grown in harsh conditions. The density of the barrel is higher. For this reason, it is worth buying a pine tree or spruce, which rose in the northern regions of the country.
You also need to pay attention to the time of the workpiece. The best is considered the period at the end of winter. At this time, the tree is in sleeping condition, it is less than juice, therefore the moisture of material will be less.
What are wooden floors
Wooden overlap beams are used for almost all levels at home. The beam frame must be provided for the following types of design:
- basement or base overlap (floor of the first floor);
- intergenerational overlap;
- clear overlap.
The thickness of the bearing timber for the attic range is from 10 to 20 cm From the type the normalized payload, which takes into account the wooden beams of overlapping. Also, the difference will be in the thickness of the insulation and its necessity.
Between the beams above the basement are usually placed from 5 to 15 cm mineral wool, foam or extruded polystyrene foam. In intermediate structures, it will be enough to provide a couple of centimeters for sound insulation. The cold attic requires the most material. Here, the thickness can be from 10 to 20 cm. The exact values \u200b\u200bdepend on the climatic area of \u200b\u200bconstruction.
Basels of basement overlap laid mineral wool Sometimes the basement is preferred to do from wood, but from metal and reinforced concrete. In this case, the beams are used as beams or a channel or a channel, and the concrete is poured into the formwork from the proflist. This option will be more reliable in the probability of flooding. It will also better resist dampness from the basement.
What are the beams
There are several signs for which the classification of wooden beams of overlaps is carried out: in size, material, type of section. The length of the ceiling beams depends on the distance between the walls. This magnitude needs to be added to the reservoir on both sides. Optimally, it is necessary to provide 200-250 mm.
By material, elements are divided into the following types:
- from a whole timber or board;
- from glued timber.
Both beams made from glued bars The latter are significantly more expensive. But this material is suitable for overlapping large spans. The usual beam can work for 4-6 m, while glueding well copes with distances 6-9 m. The glued bar practically does not give a shrinkage, fireproof and resistant to moisture action. You can make not only linear elements, but also bent. The essential disadvantage of such material will be the presence of unfulfilled components (glue).
The beam section may be the following types:
- square;
- rectangular;
- loop.
The latter has exhausted elements in the upper and lower part. In the middle of the section it is reduced to the highest possible sizes. This option allows rational to use wood and reduce its consumption. But it is not easy to make such an element. For this reason, the boutique is not so often used in construction.
Most often used rectangular beam The optimal option will be a rectangle. In this case, the long side is located vertically, and short - horizontally. This is due to the fact that an increase in height better affects the strength than widths. Install the beam from the board the plaffus is almost useless.
The most unfavorable from the submitted can be considered a square cross section. It is less than all adjacent to the effort of the effort in the element.
Also for overlapping you can use logs. But this option was not popular. The cross section from the board is much more profitable and more convenient in the installation, so it is used much more often.
Calculations
The calculation of the section will allow not to doubt the strength and stiffness of the structure. At the same time, the maximum length is determined, which is allowed with any section. To calculate the calculation, you need the following data:
- the length of the wooden beam overlap (more precisely, the distance between the carrier walls);
- distance between beams (their step);
To calculate you need to know the distance between the beams, the width of the span and the load on the design The load consists of two values: constant and temporary. Permanent involves the mass of the beams themselves (as long as the preliminary), insulation, ceiling liner, rough and clean floor. Temporary load is a lot of people and furniture. According to regulatory documents for residential premises, it is taken equal to 150 kg / m2. For the attic you can take less, but it is recommended - the same. This will not only provide a certain margin of safety, but also will provide an opportunity in the future to re-equip your attic into the attic without reconstructing the carrier elements.
Blook frame should count on such formulas:
- Mmax \u003d (Q * L2) / 8;
- Wetreb \u003d MMAX / 130.
In these formulas Q is a load on a sq. m overlap, which includes a mass of structures and 150 kg of useful value. At the same time, the specified values \u200b\u200bneed to be multiplied by the distance between the beams. This is due to the fact that for calculations you need loading to the pattern meter, and initially the value is calculated per square. L2 - the distance between carrier walls, which relies runs, taken in the square.
Knowing the wtreb, you can choose the cross section overlap. W \u003d b * h2 / 6. Knowing W, you can easily make an equation with one unknown. It is enough only to set one geometric characteristic B (the width of the section) or H (its height).
Most often, the wooden beam already has a well-known width. It is more convenient to produce it from a 50 or 100 mm width board. You can also consider the option with a composite section. It is made of several boards with a thickness of 50 mm.
The calculation in the specified case find the necessary height of the element. But there are such cases that you need to fit into a certain overlap pie, so as not to reduce the height of the premises. In this case, a cross section is added as a known value to the equation, and they are width. But the smaller the height, the more uneconomical there will be a frame of overlapping.
For tightening two or three boards, it is convenient to use metal studs with each other. At the same time, when twisting the nuts, wider washers must be used. They prevent pressing metal into a softer tree. Between the tree and steel fasteners, it is necessary to provide insulation. To do this, you can use such material as the technoelast of the EPP brand.
Wooden bars before installation need to hydroize Before using the wooden elements, they are processed by antiseptic composition. It is necessary to prevent molding and posting. It is also recommended to carry out treatment with antipirens that will increase fire safety. When describing the walls on the wall of the brick or concrete, their ends are wrapped with technoelast, linocur, waterproof or rubberoid.
The beams in the house usually belong to the rafter system or overlapping, and to get a reliable design, the operation of which can be carried out without any concerns, it is necessary to use calculator beam.
What is the calculator beams
When the walls are already connected under the second floor or under the roof, it is necessary to do, in the second case, smoothly turning into the rafting legs. At the same time, the materials should be chosen so that the load on brick or log walls does not exceed the permissible, and the strength of the structure was at the proper level. Consequently, if you are going to use wood, you need to choose the right beams from it, make calculations to determine the desired thickness and sufficient length.
Sailing or partial destruction of the overlap can serve different reasons, for example, too much a step between lags, a deflection of the crossbar, too small area of \u200b\u200btheir cross section or defects in the structure. To exclude possible excesses, it is necessary to find out the estimated load on the overlap, whether it is a base or inter-storey, after which we use the beam calculator, given their own mass. The latter may vary in concrete jumpers, the weight of which depends on the density of reinforcement, for wood and metal with a certain geometry, the mass is constant. An exception can be deprived of wood that is not used in construction work without pre-drying.
On the beam systems in floors and rafter structures have a load of force acting on the cross section, torsion, on the deflection in length. For rafters, it is also necessary to provide snow and wind load, which also create certain efforts attached to the beams. Also, it is also necessary to accurately determine the necessary step between jumpers, since too much across the crossbar will lead to an extra mass of the overlap (or roof), and too small, as mentioned above, weakens the design.
You may also be interested in an article about the calculation of the amount of unedged and edged board in Cuba:
How to calculate the load on the ceiling beam
The distance between the walls is called the span, and there are two of them in the room, and one span will necessarily be less than the other if the shape of the room is not square. Jumpers of inter-storey or attic overlap should be laid by a shorter span, the optimal length of which is from 3 to 4 meters. With a larger distance, there may be necessary beams of non-standard sizes, which will lead to some zidiness. The optimal output in this case will be the use of metal crossing.
As for the section of a wooden bar, there is a specific standard that requires that the side beams relate to as 7: 5, that is, the height is divided into 7 parts, and 5 of them must draw up the profile width. In this case, the deformation of the section is excluded, but to deviate from the above indicators, then the width exceeding the height is a deflection, or, with the opposite inconsistency - bend to the side. So that this does not work out due to the excessive length of the bar, you need to know how to calculate the load on the beam. In particular, the allowable deflection is calculated from the ratio to the jumper length, as 1: 200, that is, there must be 2 centimeters of 4 meters.
In order for the timber to be lagged under the severity of lags and flooring, as well as interior items, it is possible to pull it out of several centimeters, giving the form of the arch, in this case its height should have the appropriate reserve.
Now let's turn to the formulas. The same deflection referred to as previously calculated: F norm \u003d L / 200, where L. - The length of the span, and the 200 is a permissible distance in centimeters for each unit of seeding of the bar. For reinforced concrete beam, distributed load q. On which 400 kg / m 2 is usually equal, the calculation of the limiting bending moment is performed according to the Max \u003d (Q · L 2) / 8 formula. In this case, the number of reinforcement and its weight is determined by the following table:
Cross sections and a mass of reinforcement rods
Diameter, mm. | Cross-sectional area, cm 2, with the number of rods | Weight 1 pm, kg | Diameter, mm. |
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Wire and rod fittings |
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Class K-7 seven-level ropes |
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The load on any beam from a fairly homogeneous material is calculated for a number of formulas. To begin with, the moment of resistance w ≥ m / r is calculated. Here M. - this is the maximum bending moment of the accompanying load, and R. - Estimated resistance, which is taken from reference books depending on the material used. Since most often the beams have a rectangular shape, the moment of resistance can be calculated otherwise: W z \u003d b · h 2/6, where b. is a width of beams, and h. - Height.
What else should be known about the load on the beam
The overlap is, as a rule, is at the same time and the floor of the next floor and the ceiling of the previous one. So, you need to make it such that there is no risk to combine the upper and lower rooms by banal overlap with furniture. Especially such probability occurs at a very big step between the beams and the failure of lags (the militant floors are laid directly on the bar laid in the spans). In this case, the distance between the crossies directly depends on the thickness of the boards, for example, if it is 28 millimeters, then the board length should not be more than 50 centimeters. If you have lags, the minimum gap between the beams can reach 1 meter.
Also be sure to take into account the mass used for the floor. For example, if mats are stacked from mineral wool, the square meter of the basement will weigh from 90 to 120 kilograms, depending on the thickness of thermal insulation. The opilk concrete will increase the mass of the same area twice. The use of the same clay will make the overlap even harder because the load is 3 times more on the square meter than when laying mineral wool. Next, we should not forget about the useful load, which for inter-storey floors is 150 kilograms per square meter at least. In the attic, it is enough to take a permissible load of 75 kilograms per square.
Table of spanings of floorsThe table of spanings of the frame of the frame house helps to choose the right section of the floor lag, which means to avoid problems in the gear, creak and vibration when walking. Our home-grown approach is to take more beams - it is not economically justified. The board is cheaper than a bar, especially a large cross section. Most often the length of the floors of the floors is within 3.5-4.5 meters and, by observing the correct cross section and step, you can install a reliable overlap.
Let me remind you that the lags of the floor are set with a certain step, a multiple of the long side of the black sheath plate, namely 305 mm, 407 mm, 488 mm and 610 mm for OSB plates / plywood measuring 2240 x 1220 mm.
For steps 305 mm (12 "OC)
For steps 407 mm (16 "OC)
For steps 488 mm (19.2 "OC)
For steps 610 mm (24 "OC)
Where did the data in these tables come from?
How to work with the tables and what is a living and non-residential load?
Residential is everything that is located and moves around the overlap space: people, items. Non-residential load is the weight of building elements. For example, the weight of the floor lag and black floor plates.
It depends on what will be located on top: double bed or ordinary chair. The finishing floor covering may be light laminate, and there may be a tie of a warm floor with a tile.
Usually for residential premises, the total load is in the range of 200-250 kg per sq.m. If you plan to install a cast-iron bath, then look at its weight and add a lot of water and your beloved in it.
What breed of wood are taken these values?
Since our markets do not have the quality system and accurate determination of the timber variety, then the tables indicate values \u200b\u200bfor ordinary spruce and pines II varieties in the North American classification.
The actual size of the cross section of boards in American tables is less than European, what to do?
It's true. If the Americans say that the board with a cross section of 2 "x 6", then this is not 50.8 mm x 152.4 mm. In fact, it is 38.1 mm x 139.7 mm. Reducing the section of the board occurs as a result of drying and planing. On our panels, forest-bodies and markets are also not a furniture store. Sellers state that the board with a cross section of 50 mm x 150 mm, but in fact it can be 40-50 mm x 135-150 mm.
In order to build a reliable wooden overlap, it is necessary to correctly select the sizes of the beams, and for this you need to make their calculation. Wooden overlap beams have the following main dimensions: length and section. Their length is determined by the width of the span, which is required to be blocked, and the cross section depends on the load, which will act on them, from the length of the span and the installation step, that is, the distances between them. In this article we will look at how to independently make such a calculation and correctly select the sizes of the beams.
Calculation of wooden overlap beams
In order to determine how many wooden beams and what sizes will need for the overlap device, it is necessary:
- measure the span that they will overlap;
- decide on how to fix them on the walls (which depth they will go into the walls);
- make the calculation of the load that will act on them during operation;
- with the help of the table or the Calculator program, select a suitable step and section.
Now consider how it can be done.
Length of wooden beam overlap
The required length of the ceiling beams is determined by the sizes of that span, which they will overlap and the reserve necessary for embedding them into the wall. The flight length is easy to measure with a roulette, and the depth of embezzlement into the walls, largely depends on their material.
In houses with walls of brick or blocks, beams are usually close in the "sockets" to a depth of at least 100 mm (board) or 150 mm (timber). In wooden houses, they are usually placed in special cuts to a depth of no less than 70 mm. When using a special metal fastening (clamps, corners, brackets), the length of the beam will be equal to the span - the distance between the opposite walls on which they are attached. Sometimes, when mounting the rafting legs, the roofs directly on the wooden beams, they are released outside, beyond the limits of the walls by 30-50 cm, thus forming, thus sinks of the roof.
Optimal span that can overlap wooden beams 2.5-4 m. Maximum beam length of a cutting board or timber, that is, the span that it can overlap - 6 m. With a greater length of the span (6-12 m), it is necessary to use modern wooden Beams from glued timber or 2-way, and you can also be described on intermediate supports (walls, columns). In addition, for overlapping the spans, more than 6 m long, instead of the beams you can use wooden farms.
Determination of the load acting on overlapping
The load, acting on the overlap of wooden beams consists of a load from its own weight of the elements of overlapping (beams, interburry filling, firmware) and a constant or temporal operational load (furniture, various household devices, materials, weight of people). It, as a rule, depends on the type of overlapping and conditions of its operation. The exact calculation of such loads is quite cumbersome and performed by specialists when designing overlapping, but if you wish, you can use it yourself, you can use the simplified version below.
For an attic wooden overlap, which is not used to store things or materials, with light insulation (mineral wool or other) and the stitching permanent load (from its own weight - robust.) It is usually taken within 50 kg / m2.
Operational load (RECPL) for such overlapping (according to SNiP 2.01.07-85) will be:
70x1,3 \u003d 90 kg / m 2where 70 is the regulatory value of the load for this type of attic, kg / m2, 1.3 - stock coefficient.
The overall settlement load that will act on this attic overlap will be:
Robshch. \u003d RSU. + RECPL. \u003d 50 + 90 \u003d 130 kg \\ m 2. Surrounding in the biggest take 150 kg / m 2.
In case, a heavier insulation will be used in the design of an attic room, the material for interburst filling or the filling, and also if it is assumed to be used for storage of things or materials, that is, it will be intensively operated, the regulatory value of the load should be increased to 150 kg / kg. m2. In this case, the overall overlap load will be:
50 + 150x1.3 \u003d 245 kg / m 2, round up to 250 kg / m 2.
When using the attic space for the attic device, it is necessary to take into account the weight of the floors, partitions, furniture. In this case, the overall settlement load must be increased to 300-350 kg / m 2.
Due to the fact that the inter-wooden flooring, as a rule, includes floors in its design, and the time operational load includes the weight of a large number of household items and the maximum presence of people, it must be designed for a total load 350 - 400 kg / m 2.
Section and pitch beams of wooden overlap
Knowing the necessary length of wooden overlap beams (L) and by defining the total calculation load, you can determine the necessary cross section (or diameter) and the laying step that are related to each other. It is believed that the best is the rectangular section of the wooden ceiling beams, with a height ratio (H) and widths (S) as 1.4: 1. The width of the beams, with this, may be within 40-200 mm, and the height is 100-300 mm. The height of the beams often choose such that it corresponds to the necessary soaplitel thickness. When used as logs, their diameter may be within 11-30 cm.
Depending on the type and section of the material used, the pitch of the beams is wooden 
the ceiling can be from 30 cm to 1.2 m, but most often it is selected in the range of 0.6-1.0 m. Sometimes it is chosen so that it corresponds to the size of the plates of the insulation, stacked in the inter bind space, or the ceiling lips. In addition, in frame buildings, it is desirable that the laying step of the beams correspond to the step of the frame racks - in this case, the greatest rigidity and reliability of the design will be provided.
You can make a calculation or verification of the selected sizes of wooden beams of overlapping by reference tables (some are shown below) or using the online calculator "Calculation of wooden beams of overlapping", which is easy to find on the Internet, "scoring" the corresponding request in the search engine. In this case, it is necessary to take into account that their relative deflection for attic cessants should not be more than 1/250, and for inter-forces - 1/350.
Table 1
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Stepm \\ Span, M. |
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table 2
Table 3.
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Stepm / Span, M. |
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Table 4.
assigned after the fulfillment of a number of requirements. So the removal of the side elements of the formwork, not carrying the load on the weight of the structures, is allowed only after reaching the concrete strength that ensures the safety of the surface and the edges of the angles.
More stringent requirements are imposed on the removal of the carrier formwork of reinforced concrete structures, which is allowed to be removed only after reaching the concrete value of the project strength:
- carrier structural elements by flying up to 2 m- 50%;
- carrier structures of beams, riglels, runs, plates and sections with a span 2-6 m- not less than 70%;
- carrier structures by flying more than 6 m- not less than 80%;
- carrier structures reinforced by carrier welded frames are at least 25%.
The standard solutions of concrete conditions are considered: temperature 20 ± 5ºC and air humidity above
90%. It should be borne in mind that in practice, as a rule, real conditions do not meet standard standards, and the process of hardening the concrete is either slowed down or accelerated. For example, at a temperature of 10ºC after 7 days, the concrete pulls the strength of 40-50%, and at 5ºC - only 30-35%. In the case of hardening at a temperature of 30-35ºC, concrete after 3 days will drop 45% strength. At negative temperatures, concrete without special additives do not gain strength at all. Therefore, the decision to relaspison and load the design should be applied after testing concrete for strength.
The timing of achieving concrete of a given strength establishes a construction laboratory based on tests of control samples or non-destructive testing methods. At objects with a total work of less than 50 m 3, receiving a commodity concrete mixture from plants or installations located at a distance of no more than 20 km, it is assumed to assess the strength of concrete according to the laboratory of the manufacturer of the concrete mixture without the manufacture of control samples at the place of installation. However, this indication does not apply to responsible paired and thin-walled structures: beams, columns, slabs of floors, as well as monolithic joints of prefabricated structures.
Of course, during the construction of country houses, it usually does not measure concrete for strength, since most construction companies operating in the private house-building sector simply do not have construction laboratories. Therefore, in this case, you will have to focus on the data of the laboratory of the manufacturer of the concrete mix. Additionally, you can conduct your own tested concrete for strength. To do this, take a metal ball with a diameter of at least 20 mmi to throw from the same height on the concrete surface: control and test. In the height of the rebound ball, it will be possible to make a reservation immediately - with a large stretch, determine whether the strength of concrete has reached to the desired value.
The total estimated load in the raft reinforced concrete structure can only be allowed after the acquisition of design strength concrete.
The metal beam of overlaps in the form of a foreign profile - has a number of undeniable advantages. So with a metal 2-way beam, you can overlap large spans with a significant load. In addition, the metal steel beam is absolutely non-combustible and resistant to biological influences. However, the metal beam when exposed to an aggressive environment can corrosive, so it is required to apply a protective coating.
In most cases, in private house-building, the metal beam has hinge supports - its ends are not rigidly fixed, for example, since in the frame steel structure. The load on the overlapping with steel 2-level metal beams, taking into account its own weight, should be calculated without a screed of 350 kg / m 2 and 500 kg / m 2 with a screed.
The step between foreign metal beams is recommended to do equal to 1000 mm, however, in order to save items, it is possible to increase the step between metal beams up to1200 mm.
The following table shows the choice of the number of the 2-way metal beam at different steps and the length of the runs.
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Poly3 M. |
Poly7 M. |
Poly6 M. |
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№ отегуев at step |
№ отегуев at step |
№ отегуев at step |
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As can be seen from the table with a total load of 500 kg / m 2 and the length of the span6 m, you should have chosen a higher number, and the beam installation step should choose less.
Added: 05.26.2012 08:21
Discussion of the issue on the forum:
We flooded the overlap between the first and second floor of I-cauldron No. 12 span 6 meters with a release of 1 meter from the carrier wall of the first floor. The distance between the 2 meters of 2 meters, from the bottom between them from the reinforcement number 12, the cellular grid is connected on top of the mesh No. 5 of the cell 10 cm. Question: After how many days you can remove the formwork and after how many days you can make the masonry of the walls, including on the release?