Diagnosis and preparation of the substrate

In any type of construction, the substrate is an element that must be considered, as it is the stable based on which we will subsequently place the covering.

Therefore, the substrate must previously be analyzed to avoid possible pathologies.

Preliminary analysis

Various aspects of the substrate must be analyzed in order to ensure that it is in optimal condition:


  • In all types of substrates check for any possible planimetry defects with the help of a ruler to avoid excessive thicknesses of the material in a single application.

Planimetry is measured using a 2 m ruler, for which purpose a thickness of 5 mm must never be exceeded in any case.

  • In the case of rehabilitation substrates, if the defects are superficial they can be corrected using the same rendering mortar that will subsequently be applied.

If a greater thickness is required by way of base coat, low-resistance traditional mortars can be used to prevent the substrate from becoming detached.



  • On cement substrates, if the water slides, the substrate is non-absorbent.

On the contrary, if the water is absorbed in less than 1 minute, the substrate will be very absorbent.

– On smooth, non-absorbent substrates (ex: smooth concrete), it is advisable to apply a base coat of GECOL Primer-M to create a bonding bridge, thereby facilitating the subsequent application of the coating.

– Absorbent and very absorbent substrates must be adequately hydrated in hot dry weather and wait for the surface shine to disappear (water saturation).

Next, apply a base coat of GECOL Primer-TP diluted with water in the ratio 1:3 of water and subsequently apply the coating.



Check the hardness and stability of the substrate by exerting pressure using a sharp object and verifying if it penetrates.

  • If it only scratches the surface, the mortar is hard.
  • If, on the contrary, we can penetrate using said object, the mortar is not considered to be sufficiently cohered, in which case we must try to increase its resistance.
  • In the case of powdery substrates, it is advisable to apply a hardening coat of GECOL Primer-TP diluted in 1:3 of water.



  • For application of mortar: the accessible parts must be sounded to check if they are hollow, particularly coated surfaces.
  • If the hollow areas are very extensive, the mortar must be removed in its entirety.
  • If they are localized, they must be removed and cleaned up.
  • If in doubt, remove and clean up all the mortar until reaching the base coat.

– Check the adherence of the regularization coats, as the stresses caused during application of the final rendering coat can cause detachment thereof.

  • For application of paints: the grid test will be conducted, which consists of cutting the paint into 2 x 2 mm squares on a 10 x 10 cm surface.

If 80% of the squares remain adhered, the paint will be considered adherent, otherwise it must be entirely removed.

When the paint is applied on rough substrates or thick synthetic coatings, its adherence must be checked using a spatula. If it is easily detached, it must be removed in its entirety.



– All foreign matter must be removed (varnish, grease, wax, etc.) using GECOL Desincrustante diluted with water in the ratio 1:5.

– Likewise, all inconsistent pellicular coats less than 3 mm thick and all bituminous, epoxydic or polyurethane mixtures.

– Plaster, traces of mortar or dust, which must be removedturner using a spatula or pressurized water.

If feasible, it is advisable to apply a hardening coat of GECOL Primer-TP diluted in 1:3 of water.

  • Clean with pressurized water keeping a distance of 10 to 30 cm between the nozzle and the wall.

Pump pressure must be between 40 and 80 bars.

– Chemical strippers or traces of grease must be removed using detergent and hot water.

Rinse thoroughly using abundant water to avoid leaving traces of said detergent.

– If we must treat the accumulation of micro-organisms (molds, algae, etc.), these will be cleaned by means of brushing or scraping or using pressurized water, using a disinfectant on the entire affected surface.

– Once cleaning and drying have been completed, wait 1 to 2 days to apply the new coat.

Recommended products


Adherence primer

Acid cleaner

Warnings: The data provided by this Constructive Solution were prepared based on standard onsite installation processes. However, we recommend that you consult our Technical Department in the event of any specific circumstance info@gecol.com