Façade cladding made with lime mortar

Descripción sistema

An old single-family house located in the municipality of Alella, in the Maresme region (Barcelona), whose west-facing façade generally had blackened cladding due to mould and a skirting board dotted with old repairs that greatly spoiled the aesthetics of the whole.

The base support of the façade is a stone masonry wall on the lower part, with brickwork on the upper part.

Reason for the intervention

The Property decides to remove the old coating and replace it with a new lime-based coating, similar in colour to the original.

Challenges and constraints

“The new rendering mortar must be lime-based and suitable for application on mixed stone and brick substrates.
“It must be able to even out the substrate to a thickness of several centimetres.
“The mortar that fills the joints in the stone wall is slightly friable and therefore requires consolidation treatment.
“The work will be carried out in July, a month characterised by high temperatures. This circumstance will make it necessary to be careful during application in aspects related to the treatment of the substrate and the curing of the mortar.

Molins Solution

“Elimination and removal of the old façade cladding until the base substrate is uncovered.
“As there are no problems of capillary rising, the plinth can be treated with the same REVAT® CAL FONDO regularisation mortar (GP CSII W0 according to UNE EN 998-1) that will be used on the rest of the façade.
“The mortar joints of the stone wall will be poured and treated with PROPAM® DUR consolidant, prior to filling with REVAT® CAL FONDO mortar.
“Once the surface of the substrate has been regularised with REVAT® CAL FONDO, it will be finished with REVAT® CAL TRADITIONAL (GP CSI W2 according to UNE EN 998-1).

Execution

“Mechanical removal of the old façade cladding, until the original support is uncovered.

“Application of REVAT® CAL FONDO to regularise the surface of the brickwork on the upper part of the façade. The reinforcement with REVAT® 110 fibreglass mesh allows to homogenise the behaviour of the substrate prior to the application of the finishing mortar.

“Application of REVAT® TRADITIONAL LIME with a thickness of 10 mm on top of the REVAT® CAL FONDO layer.

“4. Thickness of regularisation mortar in the base and high temperatures require careful application and curing.

” 5. The application of REVAT® CAL FONDO on the skirting board is carried out in several coats, with a waiting period of one day between coats. Check that the REVAT® 110 fibreglass mesh is centred in the thickness of this levelling layer. The joints are previously emptied and consolidated with PROPAM® DUR.

“6. The wetting for the curing of the REVAT® TRADITIONAL LIME coating was carried out 24 hours after its application, and in a scrupulous manner, as it coincided with a heat wave, with temperatures above 40ºC. The final result, with a remarkable aesthetic finish, met the needs and requirements of the property.

Technical note

Air lime mortars
The UNE EN 459-1: 2016 standard allows the use of air lime for the preparation of mortars in building and civil works. This type of lime comes from pure limestone with a clay content of less than <5% and hardens only in contact with air. When confined or in the presence of water, it does not harden, but with the addition of silicates, natural elements, and at the same time fundamental components of cement, we achieve that the mortar thus formed develops setting and hardening times in accordance with the execution times on site.

The air lime mortars of the REVAT® CAL range have a low modulus of elasticity (they are therefore not very rigid), which makes them highly compatible with old and traditional substrates and ideal for the renovation and repair of old buildings, many of them built with materials such as stone, masonry or mixed masonry. In addition, their high water vapour permeability allows the substrate on which they are applied to “breathe”, thus helping to prevent the dreaded condensation from forming inside the building.