Instructions

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We have gathered some useful information about the installation and maintenance of wooden floors. Hopefully you will find some useful tips from here.
Please click on a topic to read more about it.

1. Installation of floorboards

It is advisable to use the services of professionals when installing floor boards. Main requirements have been outlined in the present guide, the following of which ensures a beautiful and durable wooden floor.

General requirements

Bring the floor boards to the installation site a couple of days earlier. In this way the material adjusts with the conditions of the room. Prior to that, control the relative air humidity of the room (should remain between 35-60%), because after painting works the humidity can be very high. Keep the floor boards in an unopened package on a horizontal and levelled surface. During installation and after that the temperature of the subfloor, floor material and the room must be between 18-22 °C. Relative air humidity remains between 35-60%.

During dry period (heating period in winter), the air can be very dry in residential houses, apartments and office rooms with contemporary ventilation and heating system, air humidity can even go as low as 35% RH. Excess dryness is also harmful to our health.

Thus, in dry periods we recommend to artificially increase air humidity in rooms, e.g., by using an air-moistening device.

In summer houses or rooms that are not frequently used, a heating system controlled by a moisture regulator. If air humidity exceeds the critical limit, the heating system is turned on automatically.

SUBFLOOR

Concrete floor
In case of a concrete subfloor, it must be observed that the unevenesses of the floor would correspond to the limits of norm ±2 mm for 2 m. After casting the concrete, the floor must dry for at least 1-2 months or more (depends on the thickness of the concrete layer and the drying conditions). When the installation process is started, the relative humidity must remain around 60%. The moisture of the concrete must be measured before installation. Before starting the installation works, it is advisable to slightly sand the concrete in order to remove the residue of concrete and water from concrete surface. The given method substantially improves adhesion to concrete.

Old concrete floor
If the old concrete floor is even, the unevennesses may not exceed ±2 mm in a distance of 2 m, clean and dry (max 65% RH), floor boards may be glued directly on the subfloor. If the subfloor is not even enough, see paragraph “Uneven concrete floor”. If there are doubts about the moisture content of the concrete floor, take the same measures as for moist concrete floor. See paragraph “Moist concrete floor”.

Moist concrete floor
If, despite of ventilation, the subfloor moisture content does not fit into the permitted limits, possible defective places must be searched for and fixed. The following steps must be conducted for determining the source of moisture:
* to control the condition of building’s outside moisture insulation;
* to make sure that the floor’s thermal insulation is not wet;
* to make sure that the floor’s moisture insulation is intact and properly installed;
* to make sure that moist does not come in for example from above balcony doors;
* if there is a swimming pool in the room below, make sure that the floor’s lower moisture insulation does exist and that it is in proper working order;
* to control the existence of heat and cold bridges in the floor.

If any faults have been determined after controlling the items in the list above, such faults must be fixed before installing the floor covering. If moisture content is caused by capillary moisture, the moisture insulation of the floor can improve the situation, but in this case the moisture content of the concrete floor cannot be above 6-8%.

NB! When considering this option, it must be kept in mind that the excess moisture in the subfloor is trying to emerge in any case. If the moisture cannot break away from the top, it absorbs into wall structures, causing moisture and mould damages.

Possibilities of moisture insulation:
* Epoxide undercoat – used for concrete floor moisture insulation
* Roof felt (polymer bitumen roll material) or specific adhesive materials, which are glued over the subfloor.
* It is also possible to use film and place a layer of waterproof plywood on it.

Before gluing parquet boards, the moisture barrier glue must be fully dry.

Uneven concrete floor
If the concrete floor is not even, it must be levelled or sanded, if possible. In case of minor unevennesses, it is advisable to use a diamond disc for sanding them out.

The floor is levelled with specific mixtures, taking into consideration the instructions of the manufacturer. General recommendation — use as little levelling mixture as possible and only use products of the highest quality.

Be careful when using a levelling layer for eliminating the unevennesses of the concrete, because if the levelling layer is not strong enough, the glue may tear the levelling layer loose from the concrete. The thickness of the levelling layer must be at least 5 mm. Quality mix N is suitable for levelling: Schönox DSP the strength indicator of which is 50N/mm2.

PLYWOOD OR OSB

If the floor is constructed on wooden beams or an intermediate layer of plywood or OSB board is installed on concrete. The boards must be fixed to the beams with wood screws or glued, if concrete is used. Dowels can be used for additional fixing. Dowels may not be used in case of concrete with underfloor heating, if the exact location of the heating pipeline is not known or if the thickness of the concrete layer does not exceed the length of the dowel. Using particle boards is not the best solution due to their lower moisture proof qualities and because their linear extension is different from that of wood. Upon installation, 3-5 mm expansion joints are left between the boards. Before installation, plywood boards (1525×1525 mm) should be cut in a four smaller pieces.

Wooden subfloor
First it must be controlled, it the floor board subfloor can be used as the underlay – its unevennesses on a distance of 2 m may be ±2 mm. If this requirement is not met, the floor must be levelled by filling in the concavities or sanding; in case of larger unevennesses the floor must be covered with additional layer of boards. Make sure that the subfloor is stable. Clean the subfloor before gluing, using a slightly moist cloth and cleaning agent.

Using rafters as subfloor
Subfloor beams and rafters must be stiff and the distance between them must be in correspondence with the thickness of the material. The dimensions of floor rafters must be at least 45×45 mm, maximal moisture content 12%. We recommend using 100×50 mm rafters and place them on their wider side. The optimal distance between the centres of rafters is 40 cm, i.e., the distance between rafters is 30 cm. Before installing the floor boards, it is always recommended to cover the rafters with 12 mm plywood or OSB board layer.

2.Underfloor heating

* The temperature of the parquet surface may not exceed +27 °C during heating. The temperature fluctuation in 24 h may be maximum 5 °C.
* The moisture of the concrete subfloor during installation may not be more than 1.5 weight percents.
* Maximal value of the relative humidity of the concrete is 80%.
* Cast concrete must be dried under normal circumstances for at least four weeks.
* In order to dry the concrete, the temperature of the underfloor heating is raised by 5 °C in 24 hours, until the maximum heating capacity has been reached. The concrete is dried with heating for at least 24 days.
* The underfloor heating must be switched on for additional 5 days immediately before installing the floor.
* 2-3 days before installing the floor, the temperature is gradually lowered until it is between 18-20 °C. During the period the concrete is dried with heating, the rooms must be properly ventilated.
* An underlay is always installed on concrete, which also serves as a moisture barrier. It is installed into joints and is properly taped.
* After installing solid wood parquet, the temperature is kept even for at least 72 hours, after that it is gradually raised to a suitable level.
* Fine cracks may occur into the floor during heating period. In order to keep the cracking minimal, the conditions of the room must meet the following criteria: relative humidity 40-60% and temperature 18-22 °C.
* The average thermal resistance of the solid wood parquet (14 mm) is approximately 0.13 m² K/W. For mosaic parquets (8 mm) it is approximately 0.04 m² K/W and for stave parquet (16 mm) approximately 0.09 m² K/W.
* Beech and maple parquets are not recommended to be installed into rooms with underfloor heating due to their large shrinking/expansion capacity.

3. Moisture of wooden floors

Which is the correct moisture content for wooden floors?
In Estonian climate, the moisture content of floor boards should be 7-9%, because mostly the air humidity is between 40-60%. The process of wood adapting its moisture content according to air humidity is inevitable and this is the reason for formation of cracks between floor boards (the wood is too moist) or the floor swells up (the wood is too dry). If wood boards are dried and installed properly, even and thin cracks form between the boards. However, such cracks are not disturbing, because they are barely visible. Depending on the usage of rooms and the heating system (electric convector heaters and heating elements), the air humidity can even be below 20%. If humidity level is that low, it can be harmful to our body – skin and mucosa (nose and mouth). It results in drying mouth, itchy eyes, bloody nose and disturbed sleep. In this case we strongly recommend using an air-moistening device.

Is only solid wood floor sensitive to humidity fluctuations?
No. Since wood is a living material, wooden floors either expand or shrink due to humidity fluctuations. This also applies to laminate (the lower pressed fibre layer of which is mostly made of sawdust) and solid wood parquet floors (made from wood, mostly has 3 layers and staves). However, compared to solid wood parquet, cracks are more easily created into solid wood floors. The difference is that when a crack is formed into a solid wood floor due to excess dryness, the crack disappears, if humidity content raises. The solid wood parquet floor, however, has three layers glued together and the top layer usually has 3 staves. Due to constant fluctuation of humidity, the adhesive holding the staves may fail and the stave can come loose, which spoils the floor. This hazard is especially high for solid wood parquets of Asian origin (China and Malaysia), because the air humidity in this region during production of the parquet is much higher. The products are shipped to Europe by sea and it takes approximately 2 months. Instead of fir wood, the lower layer is usually made of poplar wood and due to favourable price of the product the adhesive may be of low quality.

What is wood balance moisture?
This is a value of wood moisture content the wood achieves in a certain time at certain climatic conditions (air temperature, relative humidity).

Is there a wooden floor without drying cracks?
Basically not, because wood is natural material. Generally it is impossible to avoid the formation of cracks in winter period, but the size of the cracks can be influenced and in best cases the cracks are not visually disturbing.

4. On-site storage of wooden parquet

* Unopened parquet packs must be stored on a levelled and dry base.
* The best way to storage parquet in conditions that resemble the conditions under which the parquet is later used: temperature 18-24 °C, relative humidity 40-60%.
* Bending of parquet packs and especially boards must be avoided, because it may cause the cracking of the varnish layer or even damage the board structure.