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1. Benefits of installing the hardwood floors - wood quality
2. Ground floor preparation - conditions that the ground must satisfy
3. Substrate preparation - leveling
4. The influence of moisture on the hardwood floor
5. The process of gluing-down - different types of glues



1. Benefits of installing the hardwood floors - wood quality

Hardwood flooring hardness

It is believed that the wood is harder if it is of a higher density. The method that is often used to determine the thickness of the wood floor is called Brinell method. Hard metal pellets are pressed into the wood surfaces by force and the imprint on the surface is measured afterwards. This procedure examines the resistance to a point load.

For areas that are exposed to impact loads, such as floors for dance halls, a harder wood is used. Harder wood is oak, beech, maple, ash, and a variety of tropical species.


Resistance to scuffing

Also with this characteristic, the major role has the wood quality. The thicker the surface of the wood, the more resistant it is to scuffing.  Since only the wood has that kind of finish, the coating that is resistant to scuffing must be taken into consideration. That is literally the precondition for the hardwood floor durability.


Slip resistance

If we take apartment floors and those in the dance hall into consideration, a certain amount of slipping is allowed and desirable. For areas such as hotels, hospitals, schools, classrooms, theaters, multimedia centers, offices, shops, restaurants, department stores - all the floors of public facilities in general must be safe for walking. The EU conditions are strict in the areas for public use and for business purposes; this regulation is known as BGR 181 (3). Requirements relating to the floors in the gyms are defined according to DIN V 18032-2. These floors have to be safe for walking and should not be slippery. In order to achieve these characteristics, there are various types of instruments for the care and treatment of surfaces.


Sound insulation

First, we need to make the difference between noise impact transmitted through the floors and walls in the adjoining room, and the noise that has been spread through the air. When speaking and by the variety of noisy sounds, too we can recognize one unique sound that is spread in the area and is reflected or absorbed by the building elements, furniture and decorations. Surface characteristics are crucial when it comes to spatial acoustics: smooth and hard surfaces such as parquet floor reflect sound, soft and structured absorb it, so the optimal combination is usually made of floors and textiles. Glued hardwood floors in comparison to ceiling equally transmit the sound to the adjoining room. With floating floors, especially with elements that are of insulating character, protection against noise made by steps can be improved.


Heat transmission

Heat transfer coefficient (λ) at different types of wood ranges between 0.10 and 0.20 W/ (mK). Values that are taken into the calculation according to DIN 4 108 for deciduous species were 0.20 and for the conifer 0.13 W/(m2K) . Although a wood is relatively good at retaining heat, so we refer to these as warm floors, the coefficient of thermal conductivity is still in the domain of flooring being installed over under floor heating, that is when heat resistance is not greater than 0.15 W/(m2K). Generally, it is possible to set up all kinds of floors on under floor heating. For this purpose, we use less thick hardwood floors.



Hardwood floors are delivered and installed with average humidity of wood that matches the ambient temperature of 20 to 22 ° C with a relative humidity of 50%. In summer, the relative humidity is usually higher and in winter, it is lower. Because of the changes in wood moisture, there are usually changes in the shape of the floors: parquet floors swell in the summer and reduce the solidity in winter, which may lead to the formation of cracks. This is normal! Cupping may be reduced if the rooms are sufficiently ventilated in winter.


Moisture absorption

Water absorption of the wood depends on the speed of the wood to absorb the moisture. Wood with greater speed moisture has more gaps between its fibers, which were used for the storage of water in the form of the natural wood. This characteristic leads to the faster drying of the wood, but it also provides greater capacity to absorb. On the one hand, this can save time for the surface coating of hardwood floor, considering that the time between working on it is shorter. On the other hand, this can lead to rapid and uneven drying (especially when applying with a trowel). For these reasons, it is recommended that wood species with greater absorption (eg. beech, ash, larch) coat with a roller.



The rules that apply to the installation of hardwood floors are a bit different from the ones that are applied for walls and ceilings. On this type of the floors, the flame spreads less. Generally speaking, according to DIN 4102-4 the wood is classified as a normal flammable material, while oak hardwood floor and mosaic floor lamellas are easily flammable materials (B1) according to DIN EN 13 226. Analogously, this applies to other types of oak hardwood floors with a favorable layer of at least 8mm.


Ecological aspects

Hardwood floors have positive effects on all human’s senses. They are manufactured with low energy consumption and from renewable raw materials. Modern kind glues, tools, and instruments for treating the surface either have a very small percent of solvent or formaldehyde. People susceptible to allergies prefer hardwood floor surfaces that collect the dust the least so there is less dust mites and allergens in their environment.

2. Substrate preparation - conditions that the surface must fulfill.


Surface that will be covered with wooden floors has to be firm, sound, smooth and free of grease and dust. If the surface is cement-based, it must meet a very important requirement relating to humidity. The required moisture of the cement-based surface upon which wooden floors are going to be installed is 2% but if upon the anhydrite floor base (screeds), it is 0.5%. In case the screed is already installed with under floor heating, then these values should be reduced for 0.2%. The most reliable method of measuring the moisture in the screed is CM method with calcium - carbide that the trained person with the right tools respecting the defined procedures has to do. As an alternative, there are types of primers and new types of glues that with an expert’s advice can allow the installation of wood floor and the substrates with higher moisture content than prescribed. Such a procedure should be undertaken only after consultation with the manufacturer of the product that is going to be installed. Murexin in its range of products has, for example special PU primer 5 with which the residual moisture of up to 3.5% can be locked as well as a special glue based on modified silane (Series X Bond MS-K), which can also be used on problematic substrates.


3. Substrate Preparation - leveling


To make your floor in residential or commercial space look perfect, it needs to be planned before installing the coverings. The quality of surface preparation will allow you maximum durability and a nice aesthetic experience and comfort in your living environment. The substrate, on which final floor coverings are intended to be placed in the new buildings, is mostly concrete. Performing tolerance for concrete and cement screed is measured in centimeters, while the flooring surface require smoothness in millimeter precision so the floor can look perfect. This can be done by leveling. Mass for leveling can be used in making the necessary mild drops, leveling the surface defects, filling and repairing the damage and coating, which will provide increasing quality to surface for finishes.


Ideal smoothing of surface is achieved by the Masses used for leveling. Murexin offers a wide range of Masses for leveling, which differ by:


  • The maximum thickness of the covering up to 30 mm, which can be done in one step
  • Ultimate hardness achieved (depending on the requirements of space and ways of transferring the load by floor covering that is by its flexibility); class C20, C 25, C 30, C 40, C50
  • All Masses for leveling that are produced by Murexin are designed for indoor use (and there are masses specially designed for outdoor use), suitable for use with under floor heating.
  • Flooring / Plastic and Rubber / epoxy floors with smaller load-bearing - Mass leveling Facility Plus OS 50 (C 35, the thickness of 10 mm)
  • Loads-bearing that are expected in offices, public and exhibition spaces, with no passage for heavy vehicles are enough to treat with Mass leveling Facility Plus OS 50 35 C class, which can be poured in a layer up to 10 mm. These types of coverings are more flexible than the ceramic ones, which affect the mode of load transmission and therefore require these floor features.


Concrete or any other type of surface that has to be leveled needs to be well prepared. The preparation involves thorough cleaning of the surface, removing all kinds of impurities and collected dust. On the cleaned surface, the appropriate primer is applied and it allows adhesion of the Mass for leveling with the ground. Depending on the type of substrate, we recommend the appropriate primers: for absorbent substrates - there is Murexin Primer LF 1 (screed, concrete or gypsum raw materials); for non-absorbent substrates - there is Murexin primer D4 ( when refurbishing on non-absorbent surfaces, lacquered parquet floors, old terrazzo floors, ceramic tiles, stone slabs); for anhydrite - there is Murexin Primer PU 5 (very absorbent surfaces).


All types of the Masses for leveling are applied to the desired thickness and evenly distributed. Mass for leveling is often called self-leveling mass because of their rare consistency (almost liquid) and are very easy for the application. Mixed mass is usually poured and distributed by notched trowel of appropriate characteristics. After completion of one layer, if required to do another one, it can be accessed as soon as it can be walked on the previous layer (for about 1 - 2 hours, depending on thickness). If it is impossible to comply with this schedule of works, for longer intervals - it is necessary to apply a primer LF Murexin first.

Note: All Murexin masses for leveling can be effused by machines.

4. The influence of moisture on the hardwood floor


What affects the moisture content of the wood the most is the moisture content of the surface (substrate) as well as the environment (temperature and humidity). When installing the wood floors, depending on the type, manufacturer determines the relative humidity of the substrate on which wood can be placed as well as the moisture content of it. It is important to pay attention to the relationship between the relative humidity and room temperature and their effect on the moisture content of the wood.

20 ˚ C, rel. Humidity 50% - moisture in wood 9%;

20 ˚ C, rel. Humidity 65% - moisture in the wood is growing at 12%

The change in the moisture content of the wood will come in shorter or longer period depending on the wood structure that is on the size of the tree (or vessels through which it collects and ships moisture and nutrients) and in which water can be loaded. Roughly speaking, a piece of wood while changing its moisture content for only 1% is actually changing its dimensions, too, for 0,25% - especially width (the solid wood is less susceptible to changes in moisture content due to environment).



Temperature: 20-22˚C

Humidity: 45-55%

Moisture content in wood: 9%


Temperature: 24 ˚ C

Humidity: 70%

Moisture content in wood: 13%

4 x 0.25% = 1% => 60mm size becomes 60.6 mm

For the hardwood floors installation, four factors are very important:

9% of the moisture content

45-55% of relative humidity


Humidity of screeds to be 2%

Discrepancies in the value of any of the factors can lead to a problem.

Austrian regulations require that the installer must measure all the factors before taking the trim and properly enter them into some kind of construction diary.


5. The process of gluing-down - different types of glues


Nowadays, a great variety of different types of parquet adhesives are available on the market, each with its own purpose and suitability for a particular case (parquet dimensions, type of the wood, purpose of the space where the parquet is being laid, etc. ).

The adhesive should never be used as a tool for smoothing surfaces!

As far as the large dimension parquet is concerned, elastic adhesive must be used (such as X Murexin Bond MS-K series) in order to accept the forces that arise due to the elasticity of the lining.

When laying the parquet of an exoticorigin, it is usually recommended to use two-component adhesives based on polyurethane (PU Murexin 560).

For a “classic” parquet, the dispersion-based adhesives (Murexin M 522) are still in use although the downward trend in using this kind of adhesives continues. This type of glue is slowly overcome for two reasons - the presence of substances that cannot be classified as organic products, i.e. products with reduced emission of EC1 and water which is in collision with the coating that gets glued (wood) and the insistence on the percentage of residual moisture in the substrate and the surrounding air. These adhesives should be used according to the parquet dimensions.