INTRODUCTION
Requirements for energy-saving and high comfort feelings strongly contributed to extension of the floor heating. At the same time problems of covering the heated surfaces occurred. In addition to the requirements of traditional laying procedure of parquet where the floor heating is combined (built) with the base, further rules shall be considered. Requirements for both the covering material and applied inlaying technology are different from the usual ones.

The prescriptions to be followed in planning, implementation and operation periods are summarized. These prescriptions concern the system produced in Hungary including plastic pipes, water-heating and poured estrich layer. Requirement system of joint application of floor heating and floor covering can be divided into three main parts:
- planning
- implementation and
- operation
prescriptions.

a.) In planning it shall be considered that the parquet is thermo-insulating material. Therefore application of leafy wood and coniferous that have very bad thermo-conductivity and thickness above 15 mm shall be avoided. The best parquet is the finished parquet. The grooved parquet and mosaic parquet also can be used but much care shall be taken during laying.

b.) No insulating felt and foil underlay can be taken between concrete and floor, which is essential requirement in case of the traditional flooring.

c.) All the materials used shall be thermo-resistant and ageing resistant at temperature of the carrier line.

d.) No the distance between heating pipes may be more than 150 mm otherwise the heat distribution on surface of the floor is wrong.

e.) Heating pipes shall be placed on the whole surface even if no the heat-requirement demands it.

f.) Since the heat transfer of the floor is limited, the room shall be thermo-insulated. Insulation values shall meet the minimum requirements of heat protection specified for the houses built recently.

g.) Heating shall be planned so that water temperature in the carrier line shall not be over 50 °C even in the coldest conditions.

h.) Surface temperature of the parquet floor must not be over 28 °C the thermo-physiologic limit (sole temperature).

i.) The minimum thickness of estrich above the heating pipes shall be 45 mm; 60 mm is recommended.

a.) The humidity in the laid parquet shall not be above 7-8 % otherwise slots can be formed.

b.) The most problems occur when the parquet is laid on estrich layer being non-dried properly. Wet content in estrich shall be less than 1.8 % as specified in the background literature.

c.) Heating up can be started only when estrich is worked in and the concrete is fully set. Heating up shall be completed at 50 °C or at temperature allowed by the plans in accordance with the enclosed instructions. After switching on the heating temperature of water can be increased daily by 10 oC.

d.) Gluing results in decreasing heat-bridge between concrete-estrich and parquet. In case of gluing solvent polyurethane glue shall be used. After gluing the system shall be allowed to stand for time recommended in the instruction for use. The heat-bridge is small therefore we recommend take up self-evener material on the dried estrich layer. After drying the surface will be entirely even and provide good heat-transfer.

e.) In the middle thermal expansion gap shall be formed between estrich and wall in rooms larger than 50 m2.

a.) Relative humidity in the rooms having floor heating combined with parquet floor may not decrease below 50 %. When the air becomes too dry, wet shall be added.

b.) Heating up and cooling down shall be completed gradually to avoid the possible stresses. A five-day transition period always shall be kept.

c.) A thermo-sensor shall be built-in the forwarding water line to avoid the system heats up to temperature above the limit.

d.) Never swab the floor when clean. A hardly-wet (fog-wet) cloth can be used to wipe the surface. This system is very sensitive to any changes in wet content.

Floor heating and floor covering form a unit; they have to be studied together. A change in one part results in change in the other part. It must be considered in planning.

Floor heating and floor covering can be matched to each other. But it shall be considered in planning that parquet will be used for floor covering. In this construction much knowledge is necessary to lay the parquet and therefore can be done by skilled worker only.

Heated floor can be covered with finished parquet. Heat flowing from concrete estrich does not damage the parquet. According to the experiences no damage occurs if the prescriptions are strictly followed.

For floor heating divided (with three lamellas) oak finished parquet is recommended. No finished parquet with beech and maple wood walking surface is allowed for this purpose due to the unfavourable swelling-shrinking characteristics of the mentioned wood types.
Due to its structure the parquet with plank walking surface is not suitable for this purpose independently on wood type of the walking surface.

It shall be emphasized again:
Basic terms of successful application of prefabricated parquet on surface with floor heating are as follows:
- good cooperation between planning and implementing agents;
- skilful, careful implementation and
- operation according to the prescribed parameters.
Order:
Site of implementation:
Thickness of concrete layer: mm
Date of implementation of concreting work: year month day

Heating up procedure:
Day 1: heating by forwarding water of + 20 °C
Day 2: heating by forwarding water of + 30 °C
Day 3: heating by forwarding water of + 40 °C
Day 4: heating by forwarding water of + 50 °C
(and maximum temperature specified by the plans)

From day 5 to day 15 heating, without night break with forwarding water of maximum allowed temperature;

Day 16: decreasing heating by forwarding water of + 40 °C
Day 17: decreasing heating by forwarding water of + 30 °C
Day 18: decreasing heating by forwarding water of + 20 °C
Day 19: determination of humidity (in case of concrete layer: 1.8 %, CM method)

To measure the humidity with CM method, ask the flooring specialist for help.
Designer shall mark measuring points depending on the size of the room and samples for humidity measuring shall be taken here.


When the heating pipes are in middle of the concrete layer a break shall be kept after the cooling period. After that the heating up procedure shall be repeated. The next heating up and cooling down procedures shall be completed on days 1-4 and 16-18 as prescribed.

If the humidity in the concrete is not suitable heating shall be continued with forwarding water of 40 °C until the condition proper for laying (humidity shall be measured again) is achieved.

In case when there are more than 7-day break between cooling and starting to lay the parquet heating up process with forwarding water of 40 °C shall be repeated, at least for 2 days. After that humidity shall be measured again.

In heating and cooling procedures short ventilation shall be carried out regularly.

In drying procedure no building material and any other, surface-covering material was on the concrete surface.

The procedure is given for concrete layer of maximum 80 mm thickness.

The description specifies the minimum time required for drying to achieve the proper humidity. Extended drying time provides more secure wet content.

In case of floor heating the maximum allowed temperature for the parquet floor surface is 28 °C. Higher temperature results in damaging the surface of the hardwood.

In heating season the proper humidity in the rooms having floor covered with parquet made of NATUR wood shall be provided. For this purpose various oozing system can be used. Low humidity - below 50 % - results in harmful desiccation of the parquet and gaps between the parquet pieces and between the lamellas can be formed. In worse case certain lamellas can be released. Low humidity is harmful to the health, too.