What is a thermal bridge?

The Technical Building Code, in its Basic Document HE, section HE1, defines the thermal bridge as: 


“That area of the thermal envelope of the building in which there is evidence of a variation in the uniformity of the construction, either by:


  • A change in the thickness of the enclosure or the materials used.
  • Complete or partial penetration of construction elements with different conductivity.
  • The difference between the external and internal area of the element, etc., which leads to a reduction in thermal resistance with respect to the rest of the enclosure.”

Is it possible to start a SATE system without a starter profile?

The indications in the CTE/ DB-HS-1 must be respected prior to beginning the work and at all times:


“A waterproof barrier covering the entire thickness of the façade more than 15 cm. above the exterior ground level must be provided to prevent water rising by capillarity, or another solution that produces the same effect must be adopted”.


To avoid the transmission of humidity by capillarity and knocks, it is compulsory to set in place the starter profiles, which are placed horizontally and respecting a plinth of about 15 cm. This allows the initial laying of the slabs to be carried out in a uniform manner.


On the other hand, for the waterproofing of the base below the starter profile, we recommend the use of mortars from the GECOL Imper range.

How are the starter profiles positioned?

Horizontally at the lower limit of the area to be coated, respecting a plinth of about 15 cm to avoid the transmission of humidity by capillary rise. 


The profiles are installed before the insulation boards, which allows a uniform start to the installation of the insulation boards and thus creates a protection zone against dampness, knocks, etc.


Zinc-plated screws and dowels suitable for the surface are used for fixing. The fixings must be placed at a distance of 30 cm and at the joints or vertices not less than 15 cm. The use of GECOL Spacers is recommended for correct levelling.


The profiles should be spaced 2 to 3 mm apart to avoid possible contact due to expansion. 

Is it possible to install an underfloor heating system?

Complete the following steps:


  1. Waterproofing of the underground surface with one of the mortars from the GECOL Imper range.
  2. Laying of GECOL XPS insulation with GECOL Term adhesive mortar.
  3. Fixing of GECOL XPS insulation with GECOL Anchor plugs.
  4. Regularisation and hardening with GECOL Term + GECOL Malla.
  5. Waterproofing with GECOL Imper-E elastic mortar.
  6. Laying of the draining and filtering layer.
  7. Create a compression layer.
  8. Sealing with G#color Elastic-MS elastic mastic.
  9. Subsequently, follow the instructions for the installation of SATE at ground level.

What is the function of insulation board adhesive?

GECOL Term adhesive mortar has a triple function: 


  1. Support and affix the insulating material on the building facing.
  2. Restrict expansion, contraction and warping movements of the insulation. 
  3. Regulate or adjust the flatness of the installation by defect in the facing, provided that it is less than 10 mm measured with a 2 m ruler. 


GECOL Term adhesive can be used to install insulation boards on:


Non-regularised surfaces: 


A. Perimeter cordon plus centre pinch points 

B. Cordon with projection machine

Regularised surfaces:


Notched trowel on the back of the insulation board

What type of fixing plugs to use, and when?

GECOL offers a wide range of fixing plugs, either percussion (impact) or screwed.

The most common mechanical anchorage fasteners are:


  • GECOL Fixing plug:

Polypropylene dowel with polyamide core for percussion installation and suitable for A, B and C brackets.


Three-dimensional opening fixing plugs are recommended for hollow ceramic bricks (GECOL 3D fixing plug)


  • GECOL Fixing plug – A Impact:

Polypropylene dowel with metal core for tapping installation, suitable for brackets A, B, C and D.


  • GECOL Fixing plug – A:

Polypropylene dowel with metal core for screwed installation on supports A, B, C, D and E.


  • GECOL Fixing screw:

Plastic dowel consisting of a washer, also made of plastic, and a screw, which allows screwing insulation panels to wooden or steel sheet surfaces.

The fixings must be determined according to the type of surface: A – concrete, B – solid brick, C – hollow brick, D – lightweight concrete, E- cellular concrete.

Why should a primer coat be applied to acrylic finishes?

GECOL Cril fondo primer coat serves as a bonding bridge between the base coat of the GECOL Term mortar and the GECOL Revestcril acrylic finish coating, improving the adhesion of the latter.


It also performs the function of regularising both the absorption of the base layer that covers the insulation and finishing layers with a ribbed or rough texture, in which the colour of the background is transparent. 


As a tonal equaliser, it should be the same colour as the final finish.


For the application of the GECOL Cril fondo primer coat, the drying times of the mortar must be respected (humidity less than 3%) and the entire surface must be covered with a roller (pay maximum attention to the thickness of application).

What are considered singular points in a SATE?

The singular points on a façade are those where the greatest stress accumulates, or those that are more sensitive due to the intrinsic characteristics of the work or construction project. Key examples are, among others:


  • Doors and windows: 

For the correct application of a SATE system, it is necessary to pay special attention to the edges of window or door openings and to discontinuities between materials. 


Before the reinforced base layer is laid, singular areas (such as corners) should be reinforced with fibreglass mesh, overlapping the fibreglass mesh with the base layer mesh. 


It is also necessary to place reinforcement corners on all edges.


  • Sills:

An insulating plate should be placed under the piece that makes the sill to avoid the formation of thermal bridges.

  • Eaves and copings:

At the joints of the system between eaves, cornices and copings, a 5 mm elastic joint must be made using G#colour Elastic-MS. This will prevent the transmission of movement from these to the plates. 

According to CTE/DB-HS-1 art. Sills and upper finishes of façades:


“Parapets should be topped with copings to evacuate rainwater that reaches the top and prevent it from reaching the part of the façade immediately below it, or another solution should be adopted that produces the same effect.  

Large overhang elements must be treated as if they were roofs, in order to guarantee the waterproofing and insulation of the specific detail.”


Currently, there are several construction solutions within SATE systems which guarantee  correct detail solutions, regardless of the placement of the coping or other overhanging elements.


  • Corners:

Corners must be protected with metal or PVC profiles, which serve to reinforce these critical points, as well as making it easier to obtain an adequate verticality and uniformity for a suitable finish. 

In all cases, using corner posts with mesh is recommended.


The corners must be finished off by pressing the mesh fabric so that it penetrates the fresh mortar base layer.


It is essential to avoid the joining of the different corner strips in order to prevent horizontal cracks due to expansion.


  • Location of the scaffolding:

It is advisable to use tubular scaffolding, which should be placed in such a way that the free distance between the façade and the closest part of the scaffolding is greater than the thickness of the insulation plus 8 cm.


The anchorages of the scaffolding fixed to the façade must be threaded eyebolts which, once adjusted, must leave their heads at a distance greater than the thickness of the insulation plus 5 cm.

What are the surface specifications in a SATE system?

For the correct installation of a SATE, it is necessary to work with a suitable surface at all times. Prior treatment of said surface will therefore be the first step in the work to be carried out. 


The surface must have minimum characteristics of stability, cohesion, resistance, flatness, moisture content and cleanliness.  It must also have sufficient load-bearing capacity to resist the combined loads of its own weight and the weight contributed by the SATE, as well as the transmitted wind loads.


This surface adaptation work must be carried out conscientiously, since it will directly influence the success of the intervention. 


Surface specifications and requirements: 


  1. In new construction:
    • The surfaces must be flat (ceramic masonry with joints without protrusions, concrete or rendering mortar). 
    • Without significant irregularities, and unevenness not exceeding 10 mm under a 2 m rule.
    • With adequate strength to support the coating, and with the necessary curing time elapsed from the end of its execution, in order to meet adequate stability conditions.
    • It must be clean and consistent, absorbent and free of dust or release agents.


  1. In renovation works:
    • It must be consistent, uncracked and unaged, with all friable parts removed or repaired.
    • Remove all traces of dirt and contamination on the surface (proliferation of microorganisms, accumulations of dirt, etc.) by applying a biocide agent and then washing with pressurised clean water. 
    • Deteriorated concrete surfaces must be repaired with a mortar from the GECOL Reparatec range, including treatment of the reinforcement for possible deterioration or rust.
    • Repair cracked areas, provided that the cracks are stable and have an opening of more than 2 mm.
    • Remove the existing coat of paint.
    • The original external water, gas and electricity conduits will be maintained, allowing access to these when necessary.

Is it possible to start the SATE at floor level?

Only an insulating and moisture-resistant material such as GECOL XPS can be used for this purpose, and the steps to follow are as below:


  1. Waterproofing of the surface and plinth of the building (1 metre) with a mortar from the GECOL Imper range and execution of the half-round.
  2. Laying of GECOL XPS insulating material 10 mm from the foundation with GECOL Term adhesive mortar and subsequent sealing with G#color Elastic-MS mastic.
  3. Mechanical fixing with GECOL GECOL XPS fixing dowels.
  4. Lay the starter profile at 10 mm on the GECOL XPS insulation and then fill with G#color Elastic-MS.
  5. Installation with GECOL Term and subsequent GECOL Taco for fixing the prescribed insulation board.
  6. Regulation and stiffening of the insulation boards with GECOL Mesh 330 high reinforced anti-vandalism mesh.
  7. Laying of GECOL Mesh 160 covering the joints with GECOL Term.
  8. Application of the finish coating up to 15 mm from the foundation.
  9. Laying of ceramic skirting board with deformable adhesives (S1 or S2) from the G100 range.

How are insulation boards installed?

The insulating panels will be installed using GECOL Term adhesive mortar and will be placed in a counterpoised manner, from the bottom upwards, pressing uniformly to connect them, starting from the edges of the building. 


It is important that whole panels or half panels are placed in the corners of the building and that these are perfectly solid and adhered to the base surface.


At all times, check that the insulation boards have been correctly affixed to the surface, following the recommendations of standards EN 13499 and EN 13500. 


The mechanical fasteners (GECOL Fixing plugs) are then fitted after the insulation boards have been installed.


During installation, check that there are no protrusions or ridges between the insulation boards. If protrusions or ridges are present, remove these via sanding and subsequent cleaning.


The joints between insulation boards must be checked to ensure that they butt against each other and that they do not become clogged with adhesive.


The open spaces between panels will be filled with strips of the same insulating material.


Remove excess adhesive to avoid the formation of thermal bridges.


The hidden pipes will be marked to prevent them from being perforated by the drill when placing anchor plugs or other types of fasteners in subsequent anchoring operations.

How do you determine the number of fixing plugs to be used?

The number of fixing plugs is calculated according to the height of the building or situation (surface, edge), and length and diameter requirements will depend on the characteristics of the supporting wall and the type of insulation to be installed.


The mechanical fasteners are put in place once the insulation has been affixed and before embedding the reinforcement. The distribution of the mechanical fasteners must be regular.


In some specific systems, it will be necessary to use a larger quantity of fixing plugs after the reinforced render (e.g. GECOL TERM ceramic system).


It must be taken into account that higher wind loads occur in the corners of buildings, therefore even anchoring distribution must be ensured through using anchor dowels.


The fasteners must be placed perpendicularly (at a 90 degree angle) to the surface, ensuring that the top of the washer is perfectly aligned with the surface of the insulating material, or by using specific fasteners and drill bits for their application inside the insulating plate, subsequently covering the work with an insulating plug of the same material.


Depending on the insulating material and its dimensions, there are different ways to distribute the fasteners. Consult the technical department for more information.

What are the peculiarities of installing mineral wool insulation?

Due to the low compressive strength of this type of system, it is necessary to use GECOL PVC washers as a compressing agent, giving the construction greater strength and consistency.


It is also important to remember that anchoring using fixing plugs is always carried out inside the mineral wool, following the specific drawings. 

What is the purpose of the base layer for levelling and hardening the insulation board, and how is it put in place?

The entire process is carried out with GECOL Term hardening adhesive mortar.


The function of the base layer is to improve the mechanical performance of the SATE system and also to absorb the stresses that may be generated between the insulation boards. 


Once the insulation boards have been laid and all the singular points have been reinforced, the adhesive and regularising mortar is applied directly onto them, at an approximate thickness of 2 mm.


This reinforcement and smoothing layer is called the base layer. It is recommended to spread it with a notched trowel to regularise the surface and apply the same load at all points, as this layer provides most of the mechanical performance.


While the base layer is fresh, place the GECOL Malla reinforcing mesh (weight 160 g/m2) over it. The reinforcing mesh fabric must be pressed into the first layer of fresh mortar so that it is perfectly embedded, without folds. 

To ensure correct placement, contiguous sections of the reinforcing mesh must overlap by a minimum of 10 cm. 


If using anti-vandalism armour, this is put in place by embedding it in the base layer without overlaps, as its high surface density means this mesh cannot be double layered. 


However, this lack of possible overlaps can result in a high risk of cracking at the mesh butt joints. To avoid this, a second layer of mortar should be applied, with standard mesh embedded (160 g/m2).

Is there a colour limitation in the system?

It is recommended that the light reflection index is not less than 25 (where 0 = black and 100 = white). 


In any case, this value should be studied for each specific system, as it depends in part on the location of the building, orientation, geometry and type of insulation used.

Is it possible to apply cloths without partition and/or expansion joints?

Existing expansion joints in the building must be respected at all times, using the appropriate execution procedures.


When large areas of coating application are made, area delimiters (painter’s tape in the case of acrylic coatings and PVC beads in the case of mineral mortars) that create the effect of discontinuity should be used. This avoids splicing of materials and possible mismatched effects. 


In the case of acrylic coatings, greater care and attention must be taken when removing the painter’s tape, so as not to leave hollow areas and areas lacking adhesion through which water can penetrate. 


Can I use a mortar in areas of low temperatures?

The effect of cold on a mortar while setting and hardening delays or even annuls the hydration of the active components of the cement.

If the cold is intense, it can even freeze the mixing water, destroying the mechanical resistances of the mortar.

To work in these circumstances, the following precautions must be taken:

  • Store the bags in a weather-protected area.
  • Heat the mixing water to approximately 40ºC.
  • Protect the freshly applied mortar with plastic or canvas.
  • Apply a specific antifreeze product in the doses indicated by the manufacturer.
  • As a normal rule, it is not advisable to work in very cold seasons or with temperatures below 5ºC.

We are installing diaphanous pavements of large. To correctly redefine the sections, over what maximum surface area can I spread the adhesive?

There is no strict rule.


Once the paste has been extended over the substrate, it must be considered that there is a period after which a surface film is formed.


This film prevents the correct moistening of the ceramic and, therefore, good adherence between the adhesive and the ceramic in question.


There are several factors that accelerate the process:


Excessive heat.


Substrate with high porosity.


Strong wind.


It is therefore very important to monitor the state of the paste applied. If this film appears, it will suffice to simply smooth with the toothed trowel and never moisten the paste, as we would cause the formation of an anti-adhesive film of water.

Can I lay ceramic tiles on waterproofing executed with asphalt cloth or rubber?

One of the indispensable requirements in the installation of ceramics is that the support must be stable.


In the case of the two waterproofing systems mentioned, they show coefficients of expansion that are very different from those that any cement adhesive could have, even in the case of highly deformable adhesives (type S2).


To avoid this, it is recommended not to apply the adhesive directly on the waterproofing. Being the correct form, place a textile sheet (to avoid punctures) and then a screed of mortar or concrete.

On an irregular surface can the adhesive be used on gobs?

For the use of an adhesive, it is necessary to use the notched trowel and, therefore, this technique is contrary to the use “a globs”, since the grip weakens, since the piece is only stuck by the area of contact with the globs.


Also, by having a greater thickness of adhesive, shrinkage of the adhesive increases, considerably reducing adhesion.


It must be considered that since there is no adhesive on the entire surface, any bump or drill can break the ceramic coating. Also, a continuous transit on a hollow surface, causes that the ceramic piece loses the adherence.

Can I use a conventional adhesive, or a special one for plaster, on a plasterboard support?

No. Plasterboard is a gypsum sheet coated with a paper film which is anchored with specific profiling for forming the wall of the house. Therefore, we will need an adhesive that adheres to that paper coating and sufficiently flexible to absorb the deformabilities and bulging inherent to the wall in question.


For this, we have several options:


GECOL Extra (for conventional ceramics on laminated gypsum boards not waterproofed).


GECOL Cartón yeso, G100 Súper, G100 Flex, G100 Flexible premium (for low absorption ceramics and natural stone, on all types of laminated gypsum boards)


In any case, we recommend consulting our technical ceramics placement manuals.

What precautions should I take in a ceramic installation by dusting?

The application by dusting requires, absolutely, that the support has a high humidity index.


  • In addition, the following precautions should be taken:
  • That the support has not started its setting.
  • Previously sufficiently hydrate the support.
  • Make small work cloths.
  • Use the adhesive GECOL Espolvoreo in a homogeneous way, in which the whole wall is impregnated with product.
  • Wet the adhesive regularly so that it is sufficiently hydrated.
  • Adhere the pieces, solidifying and checking the adherence of these.
  • Let the joints breathe until the support is completely dry (do not grout until a few days have elapsed).

Why is a fast setting adhesive better?

Fast-setting adhesives, for the type of cement with which they have been designed, set at an earlier age than other adhesives with Portland cement of normal setting.


This means that the mixing water does not detrimentally interfere in the other additives that have the adhesives incorporated.


In addition, due to its rapid setting, the inclemency of the weather on the adhesion has a lower impact.


They are also indicated to avoid the appearance of stains on the surfaces of marble or other natural or artificial stones.


Our product catalogue features fast-setting adhesives with these characteristics, such as G100 Flexible rápido y GECOL Flexible fluido.

To coat a fireplace of a chimney. Should I adhere the tiles using a refractory mortar?

To fix ceramic cladding, a cementitious mortar should be used for ceramic tiles. Not only can they not be adhered using a mortar (even refractory), but the specific conditions we will find must also be taken into consideration.

  • The substrate will reach significant variations in temperature (depending on if the chimney is functioning).
  • The ceramic tiles that resist these conditions are normally ceramic tiles with low porosity.


Given all these peculiarities, we must use an adhesive that is able to withstand these extreme situations, which ensure a correct union between the coating and the substrate, without diminishing its performance over time.


For this, we have a deformable adhesive with high technical performance, fast setting, as it is G100 Flexible rápido.

I am applying a mortar, and when drying, I notice that it is very weak. Can it be due to high temperatures?

Mortars use in their composition, a hydraulic binder (cement or lime), that is, materials that harden in the presence of water.

If, due to high temperatures, the mortar loses water before hardening, the gripping material will not acquire the required strength.

So that this does not happen, it is advisable to previously moisten the support in order to refresh it and reduce the degree of water absorption in it.

In any case, it is not advisable to use hydraulic hardeners (cement or lime), when the temperature exceeds 35º (measured in the support).

I have a very unleveled substrate. Can I absorb these irregularities with the adhesive?

One of the basic requirements when using a ceramic adhesive (cement glue), is that the supports must be clean, dry, stable and on them, apply, with the help of a notched trowel, the corresponding adhesive.

The latest generation adhesives allow working in maximum thicknesses of up to 15 mm (G100 Flexible premium, G100 Flex, G100 Súper, GECOL Extra).

Or the use of specific adhesives for its application in thick layer (GECOL Capa gruesa)

If this were the case, it could be done without major problem.

If on the contrary it was necessary to regulate the support with greater thickness, it is advisable to regularize them previously with a specific mortar for this purpose, GECOL Revoco range,

On the other hand, the fact of applying more amount of adhesive grip, will not ensure greater adherence, as it will increase the shrinkage of the mortar and reduce their performance.

I have installed stoneware tiles using a specific adhesive but have had to remove some tiles to solve a problem. Why were these tiles completely clean?

Specific adhesives for laying low-absorption ceramic tiles and natural or reconstituted stone behave physically, not mechanically. This means that the fine filaments of cement cannot penetrate in ceramic tiles due to their lack of porosity.


Consequently, the adherence of these pieces occurs physically or chemically, not mechanically. On not being able to penetrate the piece, this adherence occurs superficially, but this does not mean that high adherence data are not obtained.

Can I stick ceramics on paint?

The paint is not a good ally of the adhesives for ceramics, since we have a support without porosity, with a different coefficient of expansion, which has to support in the application a high weight (adhesive + ceramic), a high humidity (adhesive) and a retraction (adhesive), so adhesion always fails.


We recommend, therefore, the removal of the paint layer.

Can I use any adhesive on a gypsum surface?

Under any concept.  The union between the cement and the gypsum is incompatible, since it gives rise to expansion phenomena of the gypsum that would cause the application to fail.


It must be considered that cement is more resistant than gypsum, due to which, when setting, it takes away part of the substrate.


In the same way it happens with other supports of similar nature, such as plaster or anhydrite.


There are adhesives on the market that make the plaster – cement tandem compatible, such as:


GECOL Yeso is a suitable product for the placement of conventional ceramics (absorption of water exceeding 3%)


GECOL Porcelánico yeso is the case of porcelain tiles or low absorption.


G100 Súper, G100 Flex y G100 Flexible premium, are valid adhesives on plaster supports if it is resistant, clean, stable, of a certain thickness (1cm) and in perfect condition of setting. In case of not being in these conditions or being of a similar nature (plaster, anhydrite, fine plaster), it is recommended to use GECOL Primer-TP adhesion primer.

Can a low-absorption ceramic be applied with a conventional adhesive?

Do not.


Porcelain stoneware and generally low absorption ceramics require adhesives rich in resins.


Unlike conventional ceramics, these barely have any degree of water absorption, so it is necessary to use chemical anchoring adhesives.


Specific products such as G100 Súper, G100 Flex y G100 Flexible premium, have this type of resins and additives for a perfect adhesion in the support with low absorption ceramics.


Therefore, we recommend consulting our technical ceramic placement manuals, for the specific choice for application needs.

What type of adhesive should I use for the placement of a ceramic on a cementitious waterproofing membrane?

Cementitious waterproofing membranes, type GECOL Imper-E o GECOL Imper-R, are increasingly used for their excellent performance, ability to waterproof, bridging small cracks, absorb the various movements of the support and the possibility of being coated directly, using a cementitious adhesive, with any type of ceramic tile.


For this, a deformable cementitious adhesive (according to EN 12004 type S1 or S2) capable of absorbing the possible elongations caused by this type of cementitious membranes in the processes for which they have been designed must be used always.


GECOL has a wide range of deformable products type S1: G100 Flex, G100 Flexible premium, G100 Flexible rápido y GECOL Flexible fluido or high deformability, type S2: GECOL Súper flexible y G100 Superflex.


The final choice of any of these adhesives is conditioned by the type of application, tile size or speed of execution.


What happens if we make a joint mortar with the consistency of a grout?

Traditionally, the ceramic grouting was done with white cement or grout, which needed a high contribution of water in the kneading.


Currently, there are mortars in the market designed for the filling of joints, much more consistent, of higher quality and final performance and requiring a smaller amount of water.


It is important to follow always the guidelines indicated by the technical specifications of G#color Junta-F PLUS, G#color Junta-G PLUS y G#color Junta premium, in terms of application and amount of mixing water.


Consequently, a high percentage of water can cause a weakening of the joint, as well as carbonations and fissures.

Is it possible to place ceramics without joints, at the end or at the bone?

It is not recommended, in any case, since when these joints are not made, the movement of the support will cause a collision between the pieces, causing the breakage or detachment of the same.


These movements are even more accentuated in supports and special circumstances such as facades, large surfaces, plasterboard, floors with radiant air conditioning, etc.

Why is it not advisable to clean the mortar from joints with esparto grass?

Esparto is a natural fiber, which in most cases fades and is dirty or dusty.


In addition, in the cleaning process will scratch the same, for all these circumstances, the final result will be a board with a color and termination very different from the desired.


Therefore, we recommend using materials and tools designed for this purpose and that are included in our technical manuals.


Is it important to dry the pebbles prior to applying one-coat pebbledash cladding?

It is of vital importance for the pebbles to be clean (washed) and dry.


We recommend washing and extending the pebbles on nets on a dry surface, moving it every now and then to ensure complete drying thereof prior to the application.


Wet or dirty pebbles will cause problems when finishing the one-coat cladding, as carbonations will appear due to the fact that the humidity of the pebbles will provide the necessary environment for the salts inherent to cementitious products to migrate outwards, appearing as white stains and altering the final finish.

Several cracks or fissures have appeared in my one-coat mortar. What could have caused them?

This is a normal pathology in coatings.


Fissures result from the movement of the materials, which may be mechanical (ex.: structural movements), hydrothermal (ex.: hot, dry weather) and chemical (ex.: appearance of salts).


When materials that work jointly in a constructive element have equivalent movements, these do not affect the behaviour of the whole.


Fissures can be classified as follows:

• Staggered fissures or cracks in teeth


These are fissures or cracks with straight sections broken into right angles coincident with the geometry of the pieces that form the rendering substrate.


They are originated by the relative movement of the bricks or blocks that constitute the masonry construction, through the mortar joints as the element that offers the least resistance.


The root of the problem must always be solved.

• Branched fissures.


Fissures that extend radially from a central point.


These fissures are due mainly to lack of adherence between the coating and the substrate, and may even hollow out.


To avoid said fissures, we recommend adequately preparing the base, which must be clean and as homogeneous as possible before applying the coating.

• Quartering fissures.


These fissures do not follow a specific direction and can be fissures with a chaotic direction.


These fissures are caused by retraction due to hydraulic dehydration.


To avoid these fissures, the mortar must be adequately cured by watering abundantly during setting to avoid dehydration and retraction fissures.

• Other causes


Large differences in elasticity between the substrate and the coating could cause major movements that the substrate is unable to absorb.


The differences in the substrate and coating expansion coefficient must be analyzed.


Fissures can also be caused as a result of not respecting the substrate’s expansion joints.


For this not to occur in the coating, we must reinforce the joints with fiberglass mesh and make it coincide with the area where the battens will be installed.


Likewise, it is advisable to use fiberglass mesh to absorb structural movements in areas where most stress is accumulated.

Where should mesh be placed in a monolayer, plastering or render coating?

In so-called special points, with correspond to areas in which stresses arising from the construction work accumulate, and which can cause the cladding to crack (points of contact between different materials, brick-concrete, frameworks, pillars, blind boxes, door and window frames, etc.).


The treatment that must be given to these areas consists of incorporating fiberglass or metallic mesh (subsequently reinforcing it), that will resist said stresses without cracking.


The type of mesh that must be used to be effective must have a mesh grid square of 10×10 mm and be alkali-resistant (GECOL Malla 90), in order to resist the aggression of the cement.

On a terracotta substrate. Can I render it using any mortar?



Yes, the terracotta block is a lightweight clay ceramic block with excellent thermal and acoustic properties.


Due to its composition and morphology, a series of precautions must be taken when applying a one-coat mortar.


Due to its high porosity, it is advisable to moisten it, especially in hot weather or with strong wind, and install the fiberglass mesh in the contact between the blocks and other materials (pillars, frameworks, lintels, block, etc.), covering at least 20 cm on either side of the joins.


We recommend applying a first coat, 4-5 mm thick, by way of primer to avoid the appearance of specters (visibility of the concrete block through the coat). Apply a second coat, approximately 1 cm thick, over the first coat, always checking that the first coat has the adequate consistency; if not, we recommend spraying it with water first.


Lastly, apply GECOL Revoco o GECOL Monocapa (in any of its ranges) following all the application instructions specified in its Technical Data Sheet.

I have a substrate rough-rendered with mortar in situ at the worksite. Can I apply a one-coat mortar over it?

The substrate on which we are going to perform our work must always be verified. In the case of mortars applied in situ at the worksite, these are mostly mortars with low cement content, due to which it is a substrate with high porosity and low resistance.


A very porous substrate may cause excessively fast drying of the one-coat mortar. In addition to fissures, excessively fast loss of water in the one-coat mortar causes loss of most of its physical properties.


A low-resistance substrate causes hollowing out due to lack of adherence, giving rise to fissures and detachments.


Therefore, we recommend priming substrates with high porosity or lack of resistance with GECOL Primer–TP before to apply GECOL Monocapa.

Can I make a plastering with a masonry mortar?

Masonry mortars, according to current regulations, are designed to execute masonry constructions (façades, walls, pillars, partitions), jointing and masonry interlocking. Therefore, when roughcasting or plastering there are a series of problems not envisaged due to their fast drying, retraction fissures, lack of adherence and superficial hardness, etc.


To avoid all these disadvantages and in favor of a correct execution of a coating or coating, GECOL has designed specific products of different nature (hydraulic binder / lime, air lime and hydraulic lime) in the GECOL Monocapa and GECOL Revoco ranges.

Why have white stains appeared on the coting mortar and what are they?

They are carbonations. When coatings containing cement or lime are applied in cold or wet weather, we run the risk that white stains may appear on their surface a few days after their application. These are due to the continuous supply and sedimentation of water-soluble salts on the coating surface.


Said salts are intrinsic and indispensable to ensure the correct hardening of the coating.


When the coating dries sufficiently fast, the salts remain in its interior. In this case, carbonation is not visible.


These stains alter the aesthetic appearance of the coating, but never its technical characteristics.


Therefore, we must avoid working in cold or rainy weather and, when this occurs, the working sections must be protected from both the rain and the cold.

What steps should I follow to apply a one-coat mortar on a concrete substrate?

In general, concrete has a very smooth surface, vitrified appearance and low porosity that prevents good adherence of mineral coatings such as one-coat mortars, which act by means of mechanical adherence.


By adding synthetic resins to mortars or by applying a bonding bridge we will achieve the necessary chemical adherence to achieve good adherence to smooth, non-porous surfaces.


Whether by adding GECOL Látex and to mortars or using, or GECOL Primer-M as a bonding bridge, these are ideal products for executing this kind of work.

On an old support and without consistency, what type of coating mortar should I use?

We must always observe our substrate, as façades become degraded over the years.


Therefore, it is essential to know the characteristics and behaviour of the materials that comprise it brick (brick, natural stone, lime mortars, one-coat mortars) in order to adequately select the new coat.


Continuous exposure to adverse weather (rain, frost, sudden temperature changes, etc.) causes natural aging of façades. To restore them, the adequate coating materials must be used, verifying the state of the substrate and its resistance.


We always recommend completely curing the masonry, emptying the joints and removing all the degraded elements, and washing with pressurized water to clean the substrate surface of fungus, dust, traces of pain, degraded parts, etc.


Regularize the substrate with GECOL Sec cal / GECOL Sec cal-H to obtain correct planimetry prior to applying the new coating.


On highly absorbent substrates and/or substrates that are easily disaggregated, we must apply a primer coat of GECOL Primer-TP diluted with water in the ratio 1:3, by way of hardener and pore sealer.


Lastly, use GECOL Revoco cal / GECOL Revoco cal-H to obtain the desired finish.


Lime mortars allow us to achieve a highly decorative coating for all types of façades and interiors, in addition to the restoring all types of buildings, even emblematic and old buildings.

With a cellular concrete support, what type of coating should be used?

Cellular concrete substrates, due to their technical characteristics such as low density and unit weight, have high porosity, which can lead to dehydration or fast absorption of the one-coat mortar mixing water, preventing the proper development of the coating’s mechanical properties.


To this end, a series of preliminary actions must be performed, such as previously moistening the substrate (without saturation it) and then letting it dry, applying the primer GECOL Primer–TP diluted with water in the ratio 1:3 as an absorption regulator and installing fiberglass mesh in the contacts between the blocks and the other materials (pillars, frameworks, lintels, block, etc.), covering at least 20 cm on either side of the joins.


We recommend applying a first coat, 4-5 mm thick, by way of primer to avoid the appearance of specters (visibility of the concrete block through the coat). Apply a second coat, approximately 1 cm thick, over the first coat, always checking that the first coat has the adequate consistency; if not, we recommend spraying it with water first.


Lastly, apply GECOL Monocapa premium, following all the application instructions specified in its Technical Data Sheet. This one-coat mortar is ideal on being a lightweight one-coat mortar, thereby contributing to the thermal insulation of the façade.

Is the use of battens in a one-coat finish mortar necessary?

The battens, in addition to offering multiple aesthetic solutions, serve to plan and separate the different work panels.


The distance between work joints is fixed by the cloth surface that can be applied at once, the maximum recommended separation between joints of 2.5 m x 7 m.


On the other hand, coating mortars (monolayers, lime plasters, etc.) do not allow “splices”, so the use of reeds is the most appropriate solution, avoiding in all cases destonifications, patches and splices, etc.

I want to renovate my façade, which has a textured plastic finish. Can I apply a product directly?

This will depend on the type of finish to be applied. 


Depending on the desired finish, select one of the following options: 


1. Maintaining a plastic finish. 

In this case, and always after checking the stability of the paint or acrylic coating, proceed to cleaning the surface with diluted GECOL Desincrustante to remove dirt, mould or algae, then rinse with water. 


Subsequently, apply a layer of up to 5 mm of GECOL Rasoplast and smooth the surface with a trowel until it is completely even. 


Once the product has dried and hardened completely, apply the decorative layer with one of the products from the GECOL Cril or GECOL Revestcril ranges, depending on the desired surface texture. 


2. Applying a mineral coating. 

If we want to plaster our façade with a single layer mortar or render, it is vital that we completely remove the plastic coating, since these materials do not form a stable surface, because they are applied in very thin layers that are not able to withstand the weight of the mineral coating and its inability to adhere to paints and acrylic coatings. 


Once this layer has been removed, apply a rendering and plastering mortar, such as GECOL Monocapa or GECOL Revoco.


I have damp along the baseboard of an interior wall. What could be the cause?

Normally, damp that appears on baseboards inside dwellings are caused by rising damp.


Damp occurs when the wall absorbs water from the ground, which rises up the wall seeking to evaporate.


This damp transports the salts contained in the ground, depositing them on the outer part of the wall.


These salts become hydrated when they come into contact with humidity, increasing in volume and causing internal breaking of the wall and its coating, degrading it.


In these cases, we recommend thoroughly curing the wall down to the base substrate, removing the salts and other impurities with GECOL Desincrustante and subsequently applying GECOL Aqua mur, GECOL Aqua mur cal o GECOL Aqua mur cal-H which is a macroporous mortar which allows the wall to breathe, thereby evaporating the rising damp.


On being a macroporous product, the salts may deposit in its cavities, preventing degradation of the final coat.


The finish applied to this product must be a scraped or rustic finish, as it does not allow a smooth finish on blocking the cavities through which the wall breathes.


This product is coating provided that the system’s permeability to water vapor is not affected.

Can I waterproof a brick factory wall with a thick layer coating mortar?

In brick masonry walls, we find that most of the time the joints therebetween the brick courses are not executed perfectly, leaving cavities between the bricks laid.


When waterproofing using thin-bed products, we have the added difficulty of filling all these cavities, normally nonfulfilling the thicknesses indicated in the Technical Data Sheets of these products for thin-bed application.


For this, the technical solution goes using the product GECOL Imper-G.


Is a thick-bed waterproofing agent, formulated using cement resistant to sulphates and aggressive water and allowing, due to its composition, sufficient thicknesses for absorbing the irregularities of the brick masonry wall.

I need to waterproof a lift shaft through which water is passing me. What is the right solution?

We find cases where the buried walls are not watertight, due to which water penetrates therethrough, endangering in many cases the installations they protect.


This water is accompanied by dissolved salts from the ground, causing various pathologies that could degrade the wall.


Many waterproofing agents such as asphalt cloths, bituminous paints or so-called rubbers do not resist the backpressure exerted by the water outside the wall.


GECOL Imper-F y GECOL Imper-G are a cementitious waterproofing agent formulated with special cements that resist dissolved salts and aggressive water, and the backpressure exerted by water.


Can I build a glass block wall using any adhesive mortar?

Due to their nature, glass blocks are non-porous, due to which we cannot build a wall with such blocks using a traditional mortar.


Neither is the use of a cementitious mortar recommended due to its high degree of retraction. In addition, its application is complicated because they tend to bulge due to the weight of the block and are normally very sticky, which makes it difficult to apply using a palette.


To this we must add the fact that we would have to use a wide-joint mortar once the adhesive has set, sufficiently flexible for finishing, due to which it would have to be executed in two steps.


For this, the technical solution goes using the product GECOL Glass. It is an adhesive mortar with added redispersible resins, highly consistent and very fine for installing and jointing glass blocks in the same operation.

What are the advantages of using a cementitious mortar in relation to typical plaster-based adhesives when building large-format partition walls?

The advantages of using a cementitious product such as GECOL Tabique cerámico with respect to gypsum or plaster-based products are significant, namely:


  • It can be applied in exteriors or in places with permanent humidity (kitchens and bathrooms), as once hardened it does not become degraded such as gypsum or plaster-based products on being attacked by water or humidity.
  • A specific material is not required in the subsequent installation of ceramic cladding, as the installation material and adhesive are of the same nature.
  • It does not attack the metallic elements of a building, as in the case of gypsum or plaster-based products.

Why use a special mortar to make a barbecue or fireplace?

A refractory mortar must be used in all those situations where high temperatures are reached, as a traditional mortar (Portland Cement, traditional aggregate) would not support them, especially those reached in the barbecue firebox.


GECOL Refractario is comprised of cement and refractory aggregate whose main characteristic is to have a high flux content which, once a high temperature (to 1150 ºC) has been reached, tends to become vitrified, thereby avoiding its degradation.

How can I isolate the air chamber in a building?

The habitual thing would be to use a mortar adhesive waterproofing to the back of the enclosure, that avoids the penetration of the water, but that maintains the permeability to the steam of the same, allowing this way a correct transpiration of the building.


On this adhesive mortar the insulation would be based on mineral wool, expanded polystyrene, extruded polystyrene, rigid mineral wool and natural cork.


From here, depending on the nature of one or another insulating material, we would use:

  • GECOL Lana Mineral is a hydrofuged mortar, additivated with plasticizers, which allows a high adhesion, both to the support and to the mineral wool insulation.
  • GECOL Term is a flexible and waterproof fibre-reinforced adhesive mortar for the adhesion of expanded polystyrene (EPS), extruded polystyrene (XPS), rigid mineral wool (LW) and natural cork insulating panels.

On Exterior Thermal Insulation Coating (ETIC), can I use a conventional mono-layer mortar as a surface hardener??

Exterior Thermal Insulation Coating Systems (ETICS), consist of the fixing of an insulating board (EPS, XPS or mineral wool) to the building support and later, it is covered with the same mortar.


It is advisable that both operations are carried out with the same product, developed specifically for this purpose.


It would consist in the use of a special mortar, formulated with redispersible resins and reinforced with fibres, of high chemical adhesion, on which the alkali resistant fiberglass mesh would be subsequently embedded.


GECOL Term is an adhesive mortar for the assembly and coating of insulating panels (EPS, XPS or mineral wool), fixed on the facade to be rehabilitated.


Thanks to its resistance and fine granulometry, it is the ideal product for the coating, hardening and final finishing of the insulating plate and mesh.

Can I joint a wall made of natural stone using a joint mortar?

There are different types of mortar in the market together, designed specifically for the grouting of ceramics and natural stone.


However, for natural stone of a baseboard or façade using joint mortar is not recommended.


Normally, the technical recommendations of jointing mortars as regards application thicknesses vary up to 20 mm, always based on the depth of the joint, which would be that of the ceramic tile (8-10 mm). In these types of applications, the natural stones are usually irregular stones both in terms of thicknesses and shapes, due to which both their application thicknesses and depth differ from those mentioned previously.


GECOL Encintado is the ideal mortar for executing this type of work, due to its additives and compensated granulometry, which confers ideal properties for execution both in terms of thicknesses and the depth established by said natural stones.


Can a leveling paste be applied to a cementitious floor with radiant heating?

Several factors must be considered when applying a leveling paste on a floor with radiant heating.


  • A previous study of the cementitious screed, normally carried out “in situ”, having to make a hardening primer and lid-pores, to obtain an adequate support.


GECOL Primer-TP is the lid-pore hardening primer suitable for obtaining a resistant, stable and with an optimal absorption degree.


  • The use of a leveling paste, capable of conforming to the temperature gradients typical of these types of supports with radiant heating.


GECOL Nivelante 10-R PLUS is the fast setting leveling paste and redispersible resins, suitable to perfectly tolerate the changes of temperature that originate in the pavement.


  • The treatment of joints, putting perimeter joints in corners and changes of plane, height or material, expansion joints, between holes of doors and structural joints that present the building.


All movement joints will be filled with elastic GECOL Elastic-MS.

  • For a homogeneous finish and avoid “craters”, it is recommended to use a barbed roller to eliminate the occluded air inside the product.


In concrete, what are the differences between aesthetic repairs and structural repairs?

Depending on the characteristics required of the different concrete elements, they may form part of the building structure or part of areas which, while requiring resistance, do not form part of the building support structure.


Therefore, considering the function fulfilled by said element, the repair can be made using GECOL Reparatec R2 in the case of the repair of a non-structural element (edge, balcony edge, repair of small voids, etc.).


Depending on the thicknesses or additional features required (fast setting, self-leveling, etc.), repair mortars of the GECOL Reparatec R4 range can be used in the same way.


If the area to be repaired is concrete that forms part of a structure (a pillar, a supporting column, a framework, etc.), it must be resolved using a mortar of the GECOL Reparatec R4 range, which are a concrete repair mortars that offers greater resistance to the loads it supports.


Why should a Grout type mortar be confined or encased?

The need met by this product must be considered. The function performed by GECOL Grout 100 is a machinery and filling anchoring function.


In order to strengthen the union between the mortar and the metallic element that must be fixed to the mortar, it is conferred slightly expansive properties that will be adequately compensated provided that it is used in confined places, thereby reinforcing the fixation.


It would not make sense to use this mortar in an open space as, given its expansive properties, it would not provide the required solution.


Can I build a brick masonry wall using a rendering mortar or adhesive mortar?

In order to build brick masonry walls, resistant and consistent products are required, such as to support all the load exerted thereon.


In general, rendering mortars and cementitious adhesives contain additives in their formulas which confer certain qualities (sprayable, redispersible resins, aerators, etc.) that interfere with the aforementioned needs. Producing failures in the consistency or resistance of the wall during execution thereof.


The GECOL Sec range are masonry mortars classified as GM2.5, GM5 and GM7.5 according to Standard EN 998-2 “Masonry mortars”, based on their final resistance (2.5 N/mm2, 5 N/mm2 and 7.5 N/mm2, respectively), which have the necessary properties for building typical masonry constructions such as screeds, walls, etc.

What are the differences between a masonry mortar and a dry concrete?

The main differences are:


1. Aggregate size:

  • Masonry mortars: maximum size 1-2 mm
  • Dry concrete maximum 12 mm
  • Final resistances
  • Masonry mortars: maximum approx. 75 kg / cm2 – 100 kg / cm2.
  • Dry concretes: from 250 kg / cm2..


These differences mark the main uses of these products.


GECOL Sec is a range of masonry mortars designed specifically for the realization of screeds and floors, construction of brick masonry walls, etc.


On the other hand, GECOL Hormigón seco is valid for the realization of non-structural applications of high resistance, such as: pavements, foundations, fillings, pipelines and various repairs and realization of concrete partitions.


What are the differences between lime mortar and cement mortar?

Mainly the fundamental difference lies its binder or hardening agent (lime or cement).


Portland cement mortars, set by the action of water and characterized by being able to achieve high mechanical resistance in shorter periods of time.


In front of these, lime mortars (air or hydraulic), can set indifferently by the action of air, or water.


In addition, its main features include the ecological character thanks to the low CO2 emissions in its manufacturing process, and the high permeability to water vapor, which prevents the sick building syndrome and to adapt better to the support due to its setting.

What are the main differences between aerated lime mortar and hydraulic lime mortar?

The main difference is the way they harden: aerated lime hardens on contact with air once it has lost its mixing water and hydraulic lime hardens on contact with water.


Aerated lime is called lime or calcium hydroxide (Ca(OH)2) and hydraulic lime is called white natural cement.


As the regards the manufacturing process, hydraulic lime requires a greater energy input than traditional calcination in its transformation process.


Aerated lime offers greater workability and flexibility due to its high fineness.


Aerated lime has high porosity, which is responsible for a maximum water vapor compensation effect in the dwelling (greater water vapor permeability), and better thermal insulation.


Hydraulic lime has greater resistance to compression, greater initial resistance and also tolerates the transfer of damp and mineral salts.


Therefore, we can conclude that aerated lime is more “eco-friendly” than hydraulic lime due to its manufacturing and permeability characteristics.


What are the differences between a bonding bridge and a primer?

The adhesion bridges improve the bond between the support and the subsequent coating, in this way we achieve full adhesion between a non-absorbent support and a mortar based on cement or lime.


The primers are very varied, we can find consolidating or hardening surface primers, which improve the resistance of our mortar; top-pore primers, which regulate the absorption of the support; coloured primers GECOL Cril fondo, used in decorative elements and partitions of work panels in the applications of GECOL Revestril; etc.


GECOL Primer-M is a bonding bridge destined solely for preparing smooth, non-absorbent concretes prior to applying a mortar.


It is additivated with mineral loads to provide a greater anchoring surface for the mortar applied.


GECOL Primer-TP is a bonding bridge in its pure form (undiluted), in applications of adherence of a ceramic tile to another ceramic tile and as a surface hardener (diluted) for application as pore-sealing agent and hardener of gypsum, mortar and concrete surfaces.

What is the difference between a setting accelerator and an antifreeze?

The difference is in the way they act on the mixture and their working temperature range. 


Accelerators, such as GECOL Acelerante, are additives that reduce the setting and hardening times of mineral coatings. They are usually used when you want to perform any of the existing finishes on the same day: trowelled, scraped, smooth, drop, etc., or because temperatures could drop below 5 ºC at the end of the working day. However, they are not able to prevent the paste from freezing, so they should not be used during periods of frost. 


On the other hand, antifreezes such as GECOL Antigel are able to prevent the mixture from freezing. They prevent the formation of ice crystals, so that the binder (cement) can retain the liquid water it needs to complete its setting and hardening process, without reducing the final strength of the preparation.