Our previous application technology article discussed the professional thermal insulation of building plinths. This article explains what additional factors we need to pay attention to when insulating plinths in the case of building renovation or new buildings, and also discusses the steps to be taken after installing the thermal insulation boards.
RAVATHERM XPS 300 WB is a closed-cell, factory-roughened, plaster-based, closed-cell polystyrene foam thermal insulation material. Its typical application is in those parts of buildings where, in addition to effective thermal insulation, high mechanical resistance and thermal insulation capacity preserved even in humid environments are required.
In the case of building renovation, the quality of the surface to be insulated (raw or plastered) and its moisture level must be assessed. If the base is constantly wet or gets wet again, it is not recommended to cover it, instead, at least. a drying or moisture-regulating plaster should be applied to the lower 30 cm strip. RAVATHERM XPS 300 WB thermal insulation may only be installed above this strip.
You also need to decide whether the thermal insulation can be installed immediately on the plinth or whether it requires preparation.
In the case of a new building, attention must also be paid to the bonding substrate. If the thermal insulation boards need to be glued for waterproofing, the type of adhesive must be selected accordingly (e.g. bitumen-based water-based solvent or non-swelling, polyurethane adhesive foam, etc.) and in this case, additional mechanical fastening cannot be made.
The supporting base must always be dry, solid, free from contamination, of appropriate – even – shape, frost-free, load-bearing, and dimensionally stable.
Installation of RAVATHERM XPS 300 WB thermal insulation on building plinths
Surface protection during construction
During the implementation of the thermal insulation system, continuous protection must be ensured; from frost and from the scorching sun. If it is known in advance that the final crusting of the thermal insulation will only occur after several weeks (or months), then a protective coating of at least 1 mm thick must be formed on the surface of the XPS thermal insulation with the adhesive of the plaster system. If the application of the top layer is not carried out until the time of winter frost loads, then it is recommended to coat the protective coating with the system primer as well.
Surface reinforcement
The continuity of the reinforcing mesh applied to the thermal insulation must be ensured with a minimum overlap of 10 cm.
If the outer plane of the plinth thermal insulation and the facade thermal insulation are the same, the reinforcement layer can be installed with a continuous mesh. In such a case, it is unnecessary and unjustified to install the metal starter profile – which otherwise forms a linear thermal bridge – under the facade THR.
If the plane of the facade THR protrudes further than the plinth, the surface reinforcing glass mesh must be properly embedded and guided along the plane deviation. In such a case, it is also unnecessary and unjustified to install a metal starter profile under the facade THR. The professional solution, in addition to ensuring a continuous mesh on the surface, is to use a water nose profile on the protruding edge in order to direct the drainage of the rainwater arch.
The first step in properly embedding the mesh is to apply the system adhesive to the properly fixed thermal insulation boards. The glass mesh must be pressed into the min. 3 mm thick adhesive by means of a suspension and the mesh must be installed without waviness or sagging with the material that has been pressed through the grid from the smoothing. In the case of overlaps, the “fresh on fresh” principle must be ensured so that the adhesive thickness ensures the regular embedding of the two layers of mesh and the surface is flat, without visible ribs.
Surface formation
The surface preparation of the plinth THRs is the same as that of the facades. After the base layer made of the surface reinforcement mesh has dried and sufficiently set – according to the technological break according to the adhesive manufacturer’s instructions – it must be sanded as necessary, dusted and then coated with the top plaster primer. After the primer has dried properly (min. 24 hours), the top plaster can be applied, processed and structured according to the product administrator’s application instructions.
Paving surface formation
In the case of surface formation with tiles, after the surface preparation/substrate formation described above, the technological instructions of the tile manufacturer must always be followed.
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