Wooden floor beams — how to use it correctly, reinforcement for beams


Wooden floor beams - what they are made of, characteristics, features of different types

In modern construction, wooden floor beams are used along with reinforced concrete or metal parts. Regardless of the variety, they must correspond to their purpose, reliably distribute the load from the roof, walls located above pieces of furniture, communications.

What are wooden floor beams made of?

For this purpose, softwood is mainly used. Larch, pine or spruce are best suited. The optimum moisture content of the material is up to 14%. Lumber with a large number of knots is discarded. Floor beams made of wood of common hardwoods have less strength and durability. The fibers of the wood should be arranged along the length. Before installation, wooden elements must be treated with fire-resistant compounds and antiseptics.

What are wood beams made of?

Characteristics of wooden floor beams

With the wrong choice of wooden floor beams, they can sag or collapse at the termination points. Well-dried softwood has acceptable characteristics for use as floor elements:

  1. Under normal operating conditions, the density of wood is 500 kg / m³, for the street and wet rooms — 600 kg / m³.
  2. The bending strength of softwood is about 75 MPa.
  3. Wooden beams are easy to use.
  4. Due to the low weight of wood structures, they exert less load on the foundation of the house.
  5. Possibility of self-installation without the use of additional expensive materials.
  6. Minor repairs can be made during operation.
  7. Lower cost compared to reinforced concrete slabs.
  8. Good maintainability.
  9. Great for building private cottages with a small span.
  10. Wood is an environmentally friendly material.

Cons of wooden floor beams:

  1. Mandatory treatment with antiseptics against the effects of fungi and mold is needed.
  2. Wood is a combustible material, therefore it requires mandatory impregnation with refractory compounds.
  3. Not suitable for buildings with large spans.
  4. In terms of permissible load, they are inferior to reinforced concrete structures.
  5. Hardwoods are not well suited for use as floor beams.
  6. Temperature fluctuations can lead to deformation of wooden elements.
  7. With a moisture content of more than 14%, the risk of critical deflection increases.

characteristics of wooden floor beams

Dimensions of wooden floor beams

The choice of section depends directly on the installation step and the length of the span. If you plan to make a ceiling on timber beams, then the minimum dimensions can be selected from the table depending on the design load. The dimensions of rectangular bars in width are 4-20 cm, in height — 10-30 cm. The diameter of the rounded log is chosen in the range from 11 to 30 cm.

The dimensions of the permissible load on the floors:

  1. For an unloaded attic space — 130-150 kg / m².
  2. Used attic space — up to 250 kg / m².
  3. Interfloor ceilings — 350-400 kg / m².

Dimensions of wooden I-beams:

  1. Transverse dimensions — from 65×200 mm to 85×280 mm.
  2. The height of DDB beams is from 200 to 320 mm.
  3. The cross section of the beam is 42×85 mm.
  4. Length — up to 6 m.

dimensions of wooden beams

Types of wooden floor beams

In the general estimate for construction, the cost of these works reaches 15-20%. Attic flooring on wooden beams allows you to reduce costs, reduce labor costs, and refuse to use the rental of lifting mechanisms. For the installation of prefabricated buildings in the private sector, coniferous beams and logs are excellent. You can use their modern counterparts from glued material and OSB-boards, strong and durable metal-wood products.

Floor board

The dimensions and characteristics of the material used should be selected based on the span length and design load. When erecting the floor of the first floor along wooden beams, it must be remembered that the height of the section, and not its width, has a greater influence on the strength characteristics and rigidity. With a length of up to 4 m, it is allowed to use a thick high-quality board of running dimensions — 50×200 mm, 50×100 mm. With a span length of 6 m or more, it is better to purchase more suitable reinforced concrete structures.

floor board

I-beam floor

I-beams are made from glued dry timber (moisture content up to 8%) and OSB boards. Materials are spliced ​​under pressure using glue (D4 or analogues). Further, the structure for the fortress is reinforced with hardware, treated with flame retardants and antiseptics. Beams for floors of this type are more expensive than natural processed timber, but they have the following advantages:

  1. Relatively light weight.
  2. I-beam wooden floor beams have high strength and reliability.
  3. Excellent dimensional accuracy.
  4. Low thermal conductivity.
  5. Wooden beams made of OSB-boards have a fire-retardant coating of the first degree.
  6. Environmental friendliness within the limits.

I-beam ceiling

LVL beam

This material is obtained by gluing several prepared sheets of wood. The technology makes it possible to obtain products of great length, which helps to build the ceiling of the second floor on wooden beams with fewer supports. At the same time, in the final, the structure will have significantly less weight in comparison with the truss system made of natural boards or timber.

Advantages of LVL beam:

  1. Beam ceilings made of LVL beams have increased strength.
  2. small mass
  3. Structure homogeneity.
  4. Moisture resistance.
  5. Large range of sizes (thickness 21-75 mm, width 40-1000 mm, length up to 12 m and more).
  6. The possibility of obtaining a bar of different original shapes.
  7. Ease of use.

Cons of LVL beam:

  1. Wooden LVL floor beams made of glued board are less environmentally friendly.
  2. When using poor quality LVL, there is a risk of delamination of the material.

Lvl timber

Combined beam

The tandem of steel parts and wood significantly expands the range of materials used in construction. A standard ceiling on wooden beams in an aerated concrete house cannot always satisfy the customer. Metal-wood components are more versatile parts, they provide lightness and increased reliability of the system, while reducing the risk of drying out. The modern MD beam is a prefabricated wooden frame structure fastened together with serrated metal plates and brackets.

Advantages of MK-beams:

  1. Combined wooden floor beams allow the construction of spans up to 10 m without additional partitions.
  2. Sagging excluded.
  3. The hidden installation of communications, the process of insulation and soundproofing are facilitated.
  4. Reducing the number of fasteners.
  5. High assembly precision.

combined beam

Four-edged timber

The load-bearing beams used in construction, depending on the number of longitudinal processed sides, are divided into two-edged, three-edged and four-edged beams. The quadrangular shape is more versatile. The calibrated workpieces machined on all sides can be used in open areas where external design plays a role. The width and thickness of a rectangular cross-section dimensions of a four-edged beam lie in the range of 100-250 mm. In addition to the square shape, beams of 125×150 mm, 150x200mm or other variations are often used.

four-edged beam

Roof carriage

This material is a two-edged timber sawn from both sides, which is laid during construction in a horizontal plane. The other two sides are rounded. Carriage — a traditional element of load-bearing structures for log cabins in the Scandinavian countries, it is made mainly of pine and larch. Double-edged beams are, in fact, intermediate links between profiled blanks and rounded logs.

carriage for the roof

rounded log

Before getting into construction, such floor beams go through several stages of processing. First, the edges are trimmed, then in the machines, with the help of a milling carriage, excess wood is removed to give the workpiece the most cylindrical shape. At the end, grooves are cut out to facilitate the joining of parts, and the part is adjusted to the required length. Due to the correct geometric shape and convenient technological cutouts, the properties of a rounded log are close to those of a profiled beam.

  rounded log

Roofing device on wooden beams

In terms of strength and other indicators, wooden supports are inferior to reinforced concrete structures, but they quite successfully fulfill their function if the technology is followed in buildings up to 4 floors. The load-bearing beams of the floor are made up to 5-6.5 m long. For convenience, they are laid in stone houses with a step that is a multiple of the size of the building block. The depth of the size of the socket under the support is 0.6-0.8h (where h is the height of the beam). The standard value is 180-200 mm, the minimum is 150 mm. The gap from the end of the beam to the wall surface is 3-6 mm.

There are the following types of embedment of wooden floor beams:

  • deaf;
  • open;
  • butt joints;
  • side connection.

Strengthening wooden floor beams from deflection

Additional work to strengthen the load-bearing structures is carried out when the condition of the wood deteriorates, when a deflection appears with indicators of more than 1:300, when the attics are rebuilt into an attic. Overlapping the attic on wooden beams can be strengthened in the following ways:

  1. Installation of wooden linings on both sides of the beam in damaged areas using through bolting.
  2. Installation of metal plates or bar prostheses treated with anti-corrosion solutions.
  3. Carbon fiber reinforcement — gluing carbon fiber tape in several layers to increase the rigidity of the beams.
  4. Reinforcement of the ends of the beam with prostheses made of wood or wood at the junction. Channels, fittings, steel strip, rods are used.
  5. Installation of trussed puffs — the use of a rod structure to create an artificial tensile force.
  6. Installation under problematic wooden beams of additional supports.
  7. Use of additional beams.
  8. Reducing the load on the floor by making changes to the roof structure.


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