Lime Plaster

35_Revoco de cal

Lime plaster



Lime plaster is one of the best materials that can be used in building renovations. Although initially more fragile than cement, over time it hardens until it acquires the consistency of limestone, which remains impermeable to rainwater, preventing it from penetrating the interior of the walls, and thus enabling the breathability of the material. property.


It is very important that homes breathe, extracting the humidity that is generated inside towards the outside, due to the use of heating, household appliances, cooking food and finally, due to people's own perspiration.


An important factor to consider, apart from atmospheric agents, is the porous nature of most construction materials, which creates an internal capillary network that causes moisture to rise in the walls.


The main thing to repair this pathology is to stop and eliminate the passage of moisture. Therefore, it is not recommended to cover the humidity but rather to eliminate it permanently.


If the building does not have waterproofing systems where the foundations rest, it is evident that it may suffer from humidity problems due to capillarity.


The humidity that rises by capillarity is combated:


  • Acting on the source


  • Intercepting the path of water


  • Avoiding capillary rise


The most effective thing is to make the walls themselves eliminate the presence of humidity. To do this, it is necessary to establish barriers, which can be mechanical or chemical, either by physically inserting the barrier into the wall or by applying products that function as a barrier.


The humidity present needs to be channeled through a coating that is permeable, and allows the water vapor that has been generated inside to evacuate to the outside.


The support, as in any intervention, must be clean, healthy, free of dust, compact, dimensionally stable and free of disintegrating parts, deteriorated by the passage of time and microorganisms and sometimes it will be necessary to assemble the mortar with fiberglass mesh. in order to avoid the appearance of cracks.


If the support is not in ideal conditions, the degree of consolidation and resistance of the support must first be established by cleaning and removing the loose parts until the healthy support is found.


It is necessary to remove the plaster to be cleaned at least half a meter above the humidity mark. Subsequently, you must clean the support and those areas that are affected by the salts, eliminating those parts in which a lack of cohesion is observed or that we consider not very resistant.


Fillings and repairs can be carried out with a natural hydraulic lime mortar, avoiding the use of cement. These are mortars that promote the capillary network and occlude spaces inside where salts can deposit, thus preventing them from rising to the surface.


A first coat of grip will be applied. Once hardened, we will apply the mortar in layers until reaching a final thickness of between 2-4 cm. If you want to give a more aesthetic finish, you can use colored mortars or paints that are breathable, silicate-based and that do not prevent water vapor from passing through.



This is one of the possible actions that can be carried out when humidity is detected in a wall of a historic building, but it should always be consulted with rehabilitation specialists who assess all those aspects that may intervene in said pathology.