Strand Woven Bamboo with adhesive on heated screed
LAYING A STRAND WOVEN BAMBOO FLOORING ON A FLOOR HEATING SYSTEM USING ADHESIVES
Instructions for the floor installer
Below you will find specifications for laying a bamboo parquet on a floor heating system which do not differ from general wooden flooring guidelines, and which are suitable for this type of use. For optimum laying, you should always observe the general bamboo parquet laying instructions in addition to any of the following specific directives; we would advise that you apply them by considering the specifications relative to the screed and the type of flooring system which has been designed.
INTRODUCTION
of the two types of floor systems which currently exist – those which use water circulation or electric radiant panels – the former is to be preferred to the second due to the particular thermal conductivity of wood. It is not possible to float but only to bond this type of flooring regardless of the circumstances. It is also important to know that the wood is subject to increased tension on a heated screed than if it were to be laid on traditional screed, meaning it will have marginally more accentuated movements; in this context, moisture control is of particular significance so that the parquet is not exposed to additional fatigue. It is therefore recommended that you install a humidifier-dehumidificaton system which reacts automatically to humidity depending on the humidity level which has been detected. Having said this, you must not forget that bamboo (like wood) is a “living” material, which always moves – more or less depending on the woody essence – and it moves when the season or temperature changes, when it is exposed to light, and when other factors are taken into account; therefore, you should consider to be normal small cracks or expansion of the material which has been laid.
SCREED
The humidity levels of the screed which are always detected by using a carbide hygrometer, should not exceed 1.5% for cement screed, and remain under 0.3% for anhydrite screed. The screed must be implemented according to the heating system manufacturer’s instructions. The screed must be extremely well implemented for this type of plant, namely:
- as flat as possible to avoid any unnecessary hollowing which would prevent the heat from being transmitted non-uniformly;
- smooth side;
- using a solid surface plane which does not require adjusting should it be necessary in one room;
- it is compactly dense and obviously dry whenever the parquet is being laid.
The screed should have an overall thickness of between six and eight mm, with a distance between the pipes and laying plane of approximately 3.5 cm; a thin screed or pipes which are too close to the surface will induce heat that will then unduly dry out the wood forcing cracks to appear. It is very important that there is a steam barrier or screen in between the regularisation layer and the thermal layer of insulation.
LAYING CONDITIONS
The screed must have undergone the drying process by switching on the system for about three weeks before it can be laid with adhesive, in any season; the temperature will be increased by approximately 5° C per day until the maximum operating temperature has been reached, and it is then left for a maximum of ten days so that any residual moisture can escape and, after this process, the screed will be cooled gradually down until it shuts down completely; the slab must remain completely cold for all of the five days prior to laying. Allow the premises to air properly throughout this process. Check the residual humidity levels of the screed before laying. The ideal ambient conditions for laying are a room temperature of between 15° and 26° C along with a humidity of between 40 and 60%, values which should be maintained post-laying as much as possible. You should wait for at least two weeks after laying before switching the system on, and must ensure that you increase the temperature gradually by no more than 4-5° C per day so that the parquet has time to settle; this is also true when it comes to shutting down the system.
LAYING PHASES
– begin the installation from the outside wall to the inner wall, and position the axles parallel to the longest wall of the room, leaving a gap between the wood and all of the walls (this includes any vertically fixed objects such as pipes) of at least 1 cm; for this reason, use wooden wedges which will be removed 24-36 hors after the laying has been finished and when the adhesive is completely dry;
– the first row of axles being laid must have the female joint facing the wall;
– spread the glue as far as possible and position the axles over the entire surface of the adhesive immediately whilst making sure that the boards do not move around on the adhesive and that they remain accurately aligned; for this type of laying, please do not apply any adhesive in between the male-female joint;
– the adhesive must be spread evenly over no less than 80% of the surface, therefore it is not advisable to squeeze the adhesive on individual surface points; spread the glue perpendicularly in the direction of how it is being laid and form an eight sided shape design using the appropriate spatula, so that the adhesive incorporates any dust which exists on the laying surface;
– then spread the axles over the flooring as you would like them to appear as a final arrangement and mix the different colour shades as you require;
– walk on or press the axles so that the axles and the under floor are in as close contact as possible;
– any adhesive residues remaining on the parquet surface should be removed instantly, because once they solidify it becomes difficult to remove them without damaging the surface finish;
– position the offset axles at least 30 cm apart from each other. Finally, attach the skirting board to the wall;
– at this stage you should fully clean the floor and allow the room to air properly;
– the floor is ready to be walked on 24-36 hours after it has been laid.
OTHER CONSIDERATIONS
once the system has been activated, it is important that the floor surface temperature does not exceed 27° C for reasons which are both associated with the stability of the parquet and the well-being of the residents inside the house. Avoid covering the parquet with (too many) carpets when using a floor heating system. The water temperature inside the pipes should not exceed 30° C. It is recommended that you install a sensor which can shut off the pump so that any damage to the parquet caused by an unexpected rise in the temperature of the water supply can be avoided.
ADHESIVES
please refer to the adhesive data sheet for details of how to use it properly. Because a bonded installation is generally preferable to floating laying when it comes to a more uniform heat transmission, bamboo laying can be laid on radiant flooring using standard dual or single component adhesive if this is also specified for heated flooring; better still is the use of silane technical adhesive; silanic adhesive is the most advanced of its type available on the market today: it can be applied with genuine ease in any conditions: it is completely free from solvents, water, and nasty odours, it has particularly low volatile organic substance (VOC) emissions, along with a low content of hazardous substances for both the surrounding areas and for the installer; moreover it remains much more elastic than standard dual component adhesive once it has solidified, meaning it encourages the wood to move around and makes it particularly suitable for laying a parquet on a floor heating system. Silanic adhesive is therefore a clean product which combines an increased yield with virtually zero waste, and compensates well for its higher cost when compared to dual component adhesive.
In any event, the adhesive should be chosen according to the specification of the type of screed which has been prepared. Refer to the adhesive data sheet for details of how to use it properly. Do not bond the parquet axles in between inside the male-female joint.
KEY PRECAUTIONS
Haste is a bad advisor when building underfloor heating systems and laying parquet on top; it is very important to increase the temperature very slowly when starting the system, so as not to subject the parquet to stress; perform the pose well; always keep an eye on the ambient humidity.