Application of single-layer mortar on thermo-clay blocks

For some years now, it has been common to use thermo-clay blocks for the construction of single-leaf external enclosures, as opposed to the typical two-leaf walls. Due to its composition and morphology, it is necessary to adopt a series of precautions for the application of a single-layer mortar.

The thermo-clay block is a lightened clay ceramic block that has very good thermal and acoustic performance.

Its technical characteristics, as well as its installation system, make it possible to reduce construction costs, save energy and create a more sustainable construction.

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The substrate must be perfectly cured, resistant, have carried out the retraction movements, and be free of dust, paint, grease, etc.

Due to its high porosity, it is advisable to moisten it, especially in hot weather or with dry wind.

PlaceREVAT® 110 GLASS FIBRE MESHin the joints of the blocks with other materials (pillars, slabs, lintels, blocks, etc…), covering at least 20 cm on each side of the joints.To do this, spread a 4 to 5 mm layer of single-layer mortar on the substrate and place the mesh on it, pressing with a trowel.


The application of the single-layer mortar on the thermo-clay block can be done manually or mechanically (spraying).

It is recommended to apply a first coat of 4 to 5 mm as a primer to avoid the appearance of spectra (manifestation of the thermo-clay block through the coating). Apply a second coat, approximately 1 cm thick, on top of the previous one. In dry and/or hot weather, it is essential to apply this layer no more than 1 or 2 hours after the first layer has been applied, in order to avoid rapid drying out and to maintain correct resistance.

Finally, carry out the final finish: scraping, trowelling, sprayed stone…


  • Do not apply when there is a risk of rain or frost.
  • Apply between +5ºC and +35ºC temperature.
  • Protect the lower parts of buildings with skirting boards or make the skirting boards with PROPAM® CAL SEC.