Doweling of thermal insulation boards


The installation of the dowels should be done at a temperature ≥ 0°С. The depth of the drilled holes must be at least with 10 mm greater than the depth of doweling of the dowel in the base, which on its side has to be at least 35 mm. Old plasters and ceramic coatings, on which the installation of the thermal insulation system is performed, cannot be viewed as a sufficient load-bearing base for the dowels. This should be taken into account when calculating the length (l) of the used dowels. It is obtained from the sum of the depth of doweling the dowel into the base (hef), the thickness of the adhesive layer and the non-bearing coatings (ttol) and the thickness of the thermal insulating layer (hD).



The mounting of the dowels is performed mandatory through an adhesive layer after sufficient curing of the adhesive (at least 24 h). When using polyurethane adhesive for bonding of the thermal insulation boards, the mounting of the dowels can start 2 h after bonding the board. The mounted dowels should stand firmly and pressing the thermal insulation board. Unsteadily caught dowels must be removed and reinstalled.

When the dowels are mounted under a reinforcing mesh, their nails should be beaten to the end, until they are leveled with the cup itself – in order to protect the dowel from penetration of moisture in its interior. In this style of mounting the cup of the dowel should be slightly sunken into the thermal insulation board, so that it forms one plane with the board. The too deep beaten cup of the dowel leads to locally increased thickness of the plaster, which when moistened, due to the longer drying time, leads to the formation of visible imprint (dark spot) on the facade.

In order for the mounted dowels not to lead to the formation of thermal bridges and to not affect the effectiveness of the thermal insulation, it should be used only quality dowels with a coefficient of heat transfer point ≤ 0,002 W/K. When using dowels with a coefficient greater than this, in addition to the heat losses, there are formed permanent bright spots on the facade with the size of the cups of the dowels.

This effect can be prevented if the dowels is mounted deeper into the thermal insulation layer so that its cup is dug about 20 mm in it and the formed opening can be covered with a cover from the insulating material. The so mounted dowels are labeled as thermo dowels. More than 10 years of practice shows, that until now there is no knows case of formation of prints of the facade when using thermo dowels (the leopard effect).

A facade with bright spots, caused by dowels with bigger coefficient of point heat transfer 

Mounting of a thermo dowel

When the dowels are beaten through reinforced plaster, after mounting their cups must be plastered, so that they are completely covered without accumulation of plaster on them.

In systems, mounted with splints, the mechanical attachment is done using horizontal bearing splints, fixed to the base with certified facade dowels with thickness of 16 mm. When installing the splints, an attention should be paid so that they are not twisted and the distance between the fixating dowels to not be greater than 30 cm. The additional fastening of the thermal insulation boards to the base is done trough banding and anchoring with certified dowels with diameter of the cup 60 mm. The mounting of the dowels is done under the reinforcing mesh.

Mounting and fixing of the thermal insulation boards with the help of splints

 The number of the necessary dowels to absorb the loads affecting the Thermal Insulation System (especially those with suction), depends on the load capacity of the part of the dowel, anchored in the base, the load capacity of the cup of the dowel, the thickness of the thermal insulation board, the placement of the dowel to the boars (in the joints between the boards or in the boards themselves).

The load bearing part of the dowel, anchored in the base, determines the so called Class of loading of the dowel (in kN). The location, the number of dowels and the place of their installation define the Class of suction resistance of the system (kN/m2).

In the following table are indicated the ways of mounting of dowels, their placement and consequently Class of loading of the dowels and Class of suction resistance of the system.

 

 

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