A very important stage in the design of a building is the calculation of the lintel over the door or window opening. In order to complete this task, it is necessary to determine in advance what type of reinforcement will be used in this case. Also important indicators are the approximate load exerted from above and the dimensions of the opening. Let's take a closer look at this issue.
During construction, openings must be reinforced with lintels
Purpose of jumpers
In order to understand how important it is to correctly calculate the door lintel, you need to find out why it is needed at all. The finished opening appears to have a frame made of the same material, but if you look deeper, it becomes obvious that its upper part has additional reinforcement; it often looks like a transverse element extending deep into the masonry on the sides; this is the lintel. Its structure must be calculated at the very beginning of construction.
The functions of this element can hardly be underestimated; these include the following tasks:
- Strengthening the wall structure. Without reinforcement, the entire structure may collapse, since it will not be easy for it to withstand the colossal load if there is a void below, this is especially true for load-bearing walls.
- Formation of the opening. The lintel creates the opening itself, since it is essentially its upper part; in brick houses, it can even determine its final shape.
- Creating a foundation for further construction. Ceilings and an extension of the wall are installed on this structure.
If necessary, you can later change the shape of the opening, but it is important to consider the location of the lintel. In this case, it will be difficult to increase the height of the opening. When expanding, it will also be necessary to extend the strengthening in accordance with the new project.
Strengthening the wall structure is the main function of the doorway lintel
When building a house, it is equally important to strengthen the opening in the load-bearing walls of a panel, brick, block or wooden house. Various methods can be used for this purpose.
Main varieties
To construct the lintel, especially durable materials are used; they can be from the same category as the wall itself, or they can be radically different from the original structure. The main condition is to ensure the strengthening of the opening, as well as the uniform distribution of the applied load. All this will help to adjust further calculations for the structure in the wall.
In order to strengthen the opening in the load-bearing wall of a panel house or any other house, the following materials can be used:
- reinforced concrete;
- metal;
- wooden beams.
Depending on the chosen option, the installation of lintels above the opening differs in technological terms. Brick structures should also be placed in a separate category; they should be considered in more detail.
The main types of lintels for strengthening a doorway
Brick
A brick lintel is used to create openings in a load-bearing wall in brick houses; it is usually used for small structures. A device of this type of construction is based on the use of a particularly strong mortar, as well as the introduction of metal rods or pipes into the masonry.
A distinctive feature of this type of construction is the ability to create spectacular arched vaults. In this case, the masonry consists of straight and wedge-like elements. The seams should be perpendicular to the exposed lower tier. All joints are tightly filled with mortar. In order for the arch to hold its shape until the solution dries completely, it is additionally reinforced with wooden spacers. This formwork is installed in advance.
In the shape of an arch, 2-3 rows are often erected. The position of each of them is determined according to a special template. To adjust individual elements, use a square and a cord. It is necessary to be equal to the center and the first row.
Brick lintel installation diagram
Reinforced concrete
To strengthen the opening in the load-bearing wall of a house, reinforced concrete lintels are most often used. A preliminary calculation allows us to determine which element will be most suitable in this case. Such reinforcement of the opening can be made directly on site using formwork, reinforcement and liquid concrete.
To speed up the process, already cast elements are most often used. In order to secure them in the load-bearing wall, it is additionally recommended to use reinforcement to strengthen the sides of the opening. In other words, the metal is laid on those areas that are in direct contact with the reinforced concrete part.
The main requirement in this case is compliance with the installation rules. The lintel must completely cover the opening and extend approximately 25 cm into the wall. The exact requirements are determined by the specific type of structure. For each type of lintel and its relationship with the width of the opening, special standards have been developed.
Mostly straight products with metal filling are used. However, in some cases, it is possible to make a lintel according to a given template, which will follow the shape of the opening and at the same time act as reinforcement for the supporting structure.
Scheme of reinforced concrete lintel
Reinforced concrete lintel layout calculator
We offer a free program for calculating the layout of reinforced concrete lintels over door and window openings in brickwork.
You will only need four parameters that you know well:
– width of the opening to be closed;
– type of wall brick (silicate or ceramic);
– whether the wall is load-bearing (whether the floor slabs rest on it).
Four simple steps:
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Metal
Strengthening a window or doorway with concrete is possible only if the load-bearing wall is necessarily reinforced; some houses can be equipped with simpler metal structures. Such jumpers are most often presented in the form of an angle profile; they are made of durable metal that can withstand pressure and tension under enormous loads on it. With the help of such corners it is very convenient to build reinforcement in a brick wall.
In order to install such a part, it is necessary to fit it to the seams in the masonry. It is not necessary to reinforce the walls on the sides with reinforcement. In this case, it is enough to place the corner only 15-20 cm deep into the wall.
Prefabricated metal lintels can be used for almost any type of structure; they can be installed directly on the construction site, without making preliminary calculations.
The easiest way to strengthen a doorway is to use a metal lintel
Metal jumper
One of the simplest and most popular ways to make a lintel is to use a support from a steel angle. This option is borrowed from brickwork technology, where metal lintels are quite common. They are used for small buildings or service structures where installing standard concrete blocks is impractical.
Metal lintels belong to the group of prefabricated parts. They are not installed ready-made, but are done in stages. At the same time, the assembly process does not take as much time as when using U-blocks, which makes this option more popular. Installation takes a little more time than installing a finished jumper. Considering that the length of standard elements is not always suitable for installation in a given location, and prefabricated elements are made individually for each opening, the advantages of metal lintels are quite convincing. In addition, you can continue work immediately after installing the jumper, which becomes a decisive factor when choosing the optimal option.
However, there are also disadvantages. The first is metal corrosion. The corner (or reinforcing bars) must be protected from contact with moisture using polymer coatings. The second drawback is the high thermal conductivity of the metal, which does not combine well with the low performance of aerated concrete. A cold bridge appears above the opening, which creates the danger of the gas blocks under the ceiling getting wet. To protect against this, use ventilation to remove moist air from the opening.
Calculation of a lintel in a wall
Exact calculations are performed during the project preparation process. To do this, you need to take into account the specifics of the building material, the potential load exerted on the opening and the features of the structure itself. The main parameters in order to make the final calculation of the reinforcement of a doorway in a load-bearing wall are:
- strength: 1.12 * part strength * material strength;
- deflection: standard moment * design length of the jumper / (10 * moment of inertia * modulus of elasticity of the material) = 1/200;
- load, including from the top masonry and floors: thickness of the opening * width of the opening * height of the masonry * specific gravity of the material;
- moment of resistance: design load/8/design material resistance;
- moment of inertia: depth of support of the jumper * moment of inertia of the material * design length of the part / (10 * modulus of elasticity of the material).
Calculation of reinforced concrete lintel in the wall
All parameters necessary to perform the calculation should be found using formulas in a certain sequence. Data for some of them can be obtained by analyzing the properties of the materials used and design data for the opening and the house as a whole.
Based on these indicators, you can get the final result, which will show all the necessary parameters for arranging a lintel for the opening of the load-bearing wall of the house. If the standards are observed, the building will not sag and will be completely safe for its operation.
Standard size range, weight and marking
The GOST dimensions of reinforced concrete lintels are as follows:
- length from 103 to 596 cm;
- height from 12 to 44 cm;
- width from 14 to 38 cm.
The weight of these structures directly depends on the dimensions and can range from 20 kilograms to 2 tons.
Reinforced concrete lintels are mounted on cement mortar. Cutting of these structures for the purpose of adjustment is not permitted. If the wall thickness is large, the opening is covered with several timber lintels, laying them parallel to one another.
Special markings help you understand the wide range of these products. It consists of three groups of alphanumeric symbols separated by a dash.
The first digit indicates the GOST number of the section. It is followed by two letters indicating the type of jumper and two numbers of its length (in decimeters). The second group of numbers contains information about the design load in kN/m. The third group of marking symbols is service and contains data on the degree of concrete density, the presence of mounting loops, the degree of seismic resistance or the class of reinforcement.
For example, let’s decipher the standard designation of a reinforced concrete jumper: 2PB22-3-p:
- 2 — section number (indicated in the GOST table);
- PB – bar lintel;
- 22 – length in decimeters (220 cm);
- 3 – bearing capacity (design load, 3 kN/m);
- p – the product has mounting loops.
To increase the load-bearing capacity of lintels, prestressed reinforcement is used. Such structures can be distinguished by the type of reinforcement indicated at the end of the marking. For example, 5PB21-27-AtV. In this case, AtV is a type of prestressed reinforcement.
