Calculate Concrete Fall: Instructions | Information on Dimensions and Prices

Calculate Concrete Fall: Instructions | Information on Dimensions and Prices

Build doors and windows safely with the concrete lintel – you will find the necessary information here. The concrete lintel is a component that is built into walls. It serves to guide the pressure forces from above around an opening in the wall. In addition, the concrete lintel is the support for all other structural elements above it.

What is a concrete fall?

A concrete lintel is a beam made of concrete and steel. It has a solid cover that can absorb all pressure forces applied. The reinforcement inside the lintel is designed to absorb the tensile forces. If a concrete lintel lies under a concrete ceiling, it is also called a “joist”. If it is above it, it is a “coating”. Beams are used for large window fronts and thick external walls made of masonry. Coverings are mostly only used on top floors as supports for the purlin beams.

Types of concrete falls

In construction, a distinction is made between two types of concrete falls:

  • Finished concrete lintel
  • formed concrete lintel

A prefabricated concrete lintel consists of a concrete beam in which reinforcement is integrated. It is easily installed during the masonry. A tool such as a crane or two supports may be required to lay it neatly. Otherwise, finished concrete lintels are very easy to lay. However, you have to be very careful to put them the right way up. That is why many precast lintels are clearly marked.

A concrete lintel is a component that is only manufactured on the construction site. It is used for construction elements for which a prefabricated concrete lintel is out of the question. A typical example of a concrete lintel is a garage door: If a masonry garage is to be built rather than a prefabricated garage, a stable concrete beam is required to span the large driveway. For this purpose, a concrete lintel is formed, reinforced and concreted on site.

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What is important in a concrete fall?

A concrete fall must absorb high compressive forces from its own weight and components above it and dissipate it into the ground via its supports. As a beam that rests on two supports and has to withstand high compressive forces, a concrete fall is primarily subject to bending. A deflection exerts the greatest TENSILE FORCE on the BOTTOM of a lintel. Therefore, in the event of a fall, it must always be ensured that the reinforcement of the lintel lies strongly on the UNDER SIDE. A finished lintel, the reinforcement of which has been turned on top (or completely wrong: on the left or right side), will break through sooner or later.

Because of the reinforcement, it is by no means a matter of indifference how the lintel can be turned. A lintel has only one correct position: The continuous reinforcement bars or the majority of the bars on the underside!

This is very important when calculating the concrete lintel, as the formats allow a different laying. A prefabricated concrete lintel is intended for manual installation in a brick wall. That is why the dimensions correspond to the wall thicknesses used. The narrowest concrete lintels are 11.5 cm wide. This means that they can not only be used for narrow partition walls. If they are laid the right way around, there is nothing to prevent two or three concrete lintels being walled up next to each other.

Two concrete lintels next to each other are suitable for wall thicknesses of 24 cm, three narrow concrete lintels next to each other can be used for wall thicknesses of 36.5 cm. The next wider format is 17.5 cm wide, corresponding to the wall thickness. Two 17.5 lintels next to each other create a support surface for the opening in a 36.5 cm thick wall. The building materials trade offers “mortar brakes” for laying several lintels next to each other. This closes the joint between the lintels and can be filled with mortar. That makes it much easier to continue building over the lintel.

In the case of statically non-load-bearing walls, calculating the concrete lintel is quite simple: the lintel must be at least 25 cm on both sides and fit into the wall in terms of width. It should not protrude, otherwise the wall will have to be plastered far too thick to create a level surface. What is important, however, is that the lintel support must not end on a joint. The stone lying under the lintel must be hit in the middle and have an overlap of at least 12.5 cm on both sides. Only then will the applied vertical forces be reliably distributed logarithmically over the width of the wall.

Suitable, simple concrete lintels are available up to a span of 1.60 m. Above that, lintels with a pre-tensioned reinforcement are used. Their use should be approved in advance by a structural engineer.

Flat camber

Flat falls, as their name suggests, are falls that are wider than they are tall. They are used for statically unloaded or only very lightly loaded walls. Intermediate doors in walls made of perforated bricks are a good example of this. Due to their statically unfavorable geometry, flat lintels are in no way suitable for installation in load-bearing walls or for heavy bricks. If in doubt, you should also seek advice from a structural engineer.

Switched lintel

Laying a concrete beam over a large distance is a task that must be calculated beforehand by a structural engineer. It is more than negligent to attempt this task as a layman. An error in calculating the concrete fall leads to a destabilization of the entire structure. If you really want to save yourself the structural engineer, you can only use a double-T steel beam instead of a concrete lintel. Its purchase, transport and installation, however, should exceed the costs for a structural engineer.

A formed concrete lintel consists of:

  • Lateral brick supports
  • Sufficient coverage
  • timbered and supported formwork
  • precisely calculated, executed and inserted reinforcement
  • bubble-free concrete filling
  • If necessary, insulation on the front

For the correct execution of a concrete fall, you should at least get the support of a trained concrete worker. This task is not for laypeople. A mistake can quickly lead to demolition and thus very expensive follow-up costs!

The practical thing about a shuttered concrete beam is that it can be manufactured on site but is then a highly resilient component. Even if it is concreted completely manually with buckets, it is afterwards a continuous and precisely designed component that will serve its purpose.

Alternatives to falling concrete

Before the invention of reinforced concrete, bridging openings was always a structural challenge. It was solved either with continuous, well-hewn stones or the installation of round arches. The round and pointed arches on classic buildings were therefore not originally intended for decoration, but were the only way to produce such large gates and windows. The concrete lintel made bridging openings much easier, so that a lot could be standardized in the entire construction industry. Only the fall of the concrete made standardized windows and doors possible. Round arches are still popular today, but they are usually also reinforced concrete bodies.

Dimensions and prices

The dimensions of prefabricated concrete lintels are regulated in DIN 1045-1. Due to the standardized mass production and the inexpensive materials, they are extremely cheap. So, if a fall falls and breaks while loading, it is usually not a financial problem.

The concrete falls are divided into “MS” and “S” types. The standard width for a concrete lintel is 11.5 cm. They are given with and without additional insulation. The usual dimensions and prices for 11.5 cm wide and 19 cm high prefabricated concrete lintels are as follows:

  • MS 17: 97 cm length / 13.50 euros
  • MS 27: 119 cm length / 17.00 euros
  • MS 37: 149 cm length / 24.00 euros
  • MS 47: 189 cm length / 33.00 euros
  • MS 57: 219 cm length / 38.00 euros
  • MS 67: 259 cm length / 46.00 euros
  • MS 77: 299 cm length / 53.50 euros
  • MS 87: 329 cm length / 60.50 euros
  • MS 97: 359 cm length / 68.00 euros

Dimensions and prices of 17.5 cm wide lintels

The choice of wider lintels than the standard 11.5 lintel is slightly smaller. The 17.5 cm wide lintels are also 19 cm high. They are offered in the types MS 19 – MS 99 in lengths of 0.94 – 3.59 m. In any case, an additional crane is required to lay them. They cost between 18 and 100 euros each.

The dimensions and prices of formed lintels are based on the cost of their production and the amount of material required. One cubic meter of concrete costs around 80 euros. Reinforcing bars cost between 380 and 550 euros per ton. The assembly ex works also costs. As a layman, you are well advised to have the entire basket made by specialists in the structural steel trade. There you will find the competence to bend and braid the reinforcing steel exactly according to the static plan. Finally, the formwork has to be manufactured and supported. Depending on the size of the concrete lintel, the use of a concrete pump makes sense. In addition, an internal vibrator should be available so that the lintel can also be concreted without bubbles.

Concreting an efficient approach when concreting

Good planning and efficient preparation pay off when concreting. The smallest purchase quantity is six cubic meters, recognizable by the three-axle concrete conveyor. It is therefore advisable to have the appropriate volume of open formwork ready when the concrete truck arrives. No concrete driver likes it when mixed concrete in the car is not completely removed. There is always the risk that the concrete in the car will harden – which then makes the whole drum unusable. A concrete fall seldom has such a large removal volume. It is therefore advisable to cover the lintel together with a large concreting measure. If, for example, a false ceiling or a terrace is to be concreted at the same time as the lintel, the cement plant will also be happy to have a smart and forward-looking customer.