Restoration with macroporous dehumidifying mortar in Valls municipal library

System description

At St. Molins, committed to maintaining historic and emblematic buildings, we are very proud to have participated in the restoration of the first popular library inaugurated by the Mancomunitat of Catalonia in 1918, the Municipal Library of Valls, which is located at the top of the Passeig dels Capuchins. This building, the work of the architect Lluís Planas, is fully in line with the ideology of the noucentista period, which defined libraries as temples of culture. It is the sobriety and simplicity of its lines that give the building a sense of solemnity and grandeur, a great example of early 20th-century noucentisme architecture.

Reason for the intervention

The reason for the intervention was the high level of deterioration of the façade, especially the entire surrounding plinth, due to rising damp. A thorough restoration was necessary and the requirement was to maintain the aesthetics of the original façade and, therefore, to recover the protruding thickness of the skirting boards with respect to the façade.

A mortar with dehumidifying, macroporous and breathable characteristics was needed, which was also impermeable to rainwater and would allow high thicknesses, with a certain capacity to be moulded and worked.

Challenges and constraints

The added difficulty, as we have already mentioned, was the intended thickness of the work, as the plinths protruded more than the vertical face of the entire façade, and in order to maintain the original appearance, they had to be raised by 8 to 10 cm. Another special feature was that it was to have a double plinth and its finish was to be rounded like the original decoration.

Molins Solution

The product chosen belongs to the family of waterproofing products, PROPAM® CAL SEC, given its special feature of releasing capillary damp from the ground through steam, thus preventing deterioration of the façade, improving and increasing the healthiness of the building. PROPAM® CAL SEC also belongs to a range of exclusive products chosen for their great effectiveness, quality, maximum performance and ease of application, the PROPAM TEC range, a selection of essential products to improve the image of the home inside and out, in a context in which the health crisis has made us focus on the care of our homes and has led us to increase the number of renovations.

Execution

The rehabilitation work was carried out by the brigade of the municipality of Valls, with extensive experience in the use of lime mortars and rehabilitation and in particular PROPAM® CAL SEC.
The execution was carried out as follows:

“1. Repointing and cleaning of the entire perimeter plinth of the entire building up to its masonry base support, in many cases already removed without great effort due to the action of salts and saltpetre coming from the ground and deposited in the mortar by capillary damp. It is always appropriate to repoint 50 cm above the stain left by rising damp.

“Once the disintegrable particles had been eliminated, PROPAM® CAL SEC was applied in thicknesses of approximately 2-3 cm, placing glass fibre reinforcement mesh and alkali-resistant, REVAT® MALLA FIBRA DE VIDRIO 110 . This was embedded in the thickness of the cladding in order to distribute the stresses produced in the façade; it is important to overlap the mesh placed between each section by 10 cm. This operation was carried out up to 3 times in order to reach the required thickness, in some cases up to 10 cm.

“3. At the end of the double plinth, reinforcing mesh was also bandaged to spread the stresses at this point.

“Only the final coat was left smooth, the intermediate coats were left with a certain roughness for the convenient anchorage of the subsequent coat and not allowing more than 24 hours to pass between coats.

“Although PROPAM® CAL SEC is rainwaterproof and decorative, it was finished with silicate paint to maintain breathability and to leave a similar colour to the façade.

Technical note

Damp due to rising damp is one of the biggest problems in old and not so old buildings where the impediments were not put in place to prevent it from occurring. The fact is that the foundation is in direct contact with the water table. The water rises through the capillaries of the wall materials due to a liquid phenomenon called surface tension. The surface tension around the perimeter of these capillaries produces a force with a vertical component causing the water to rise within the capillary until the weight of the water column balances the vertical force generated by the surface tension.

The height reached by rising damp depends on several factors. The diameter of the capillaries and the evaporation that occurs on both sides of the wall. In principle, the stain “stops” as soon as the amount of water that is absorbed from the foundation equals the amount of water that the wall is able to evaporate. Therefore, the greater the evaporation capacity of the wall, and therefore of the mortar with which it is coated, the lower the height reached.
The evaporation rate therefore depends on the ambient relative humidity, temperature, porosity and permeability of the materials used, etc.

Capillary water carries dissolved salts, which, when deposited on the surfaces of building elements, cause whitish stains, commonly known as efflorescence or saltpetre.

These deposits in the internal pores of the material can initiate expansive crystallisation processes, increasing its volume and creating strong tensions that cause the pore to open. The materials that suffer from it show important flaking, thus in plasters there is a generalised loss of resistance (sandblasting) and in bricks, layers of a few millimetres are easily detached.

When these salts are deposited inside the elements, they occupy the capillary network, giving rise to cryptoflorescences.

Molins, thanks to its R&D team, has managed to develop one of the most ideal products to prevent this pathology. The product PROPAM CAL SEC, a breathable mortar for the restoration of walls, has one of the lowest permeability coefficients on the market, which makes it highly breathable to water vapour. Even so, it is a product that is impermeable to rainwater and can therefore be applied to the entire façade.

Its main characteristics are:
” Decorative (white with the possibility of finishes).
” Waterproof.
“ Projectable.
“ Sulphoresistant.
“ Effective from a thickness of 10 mm.
“ Longer working time.
“ No shrinkage (<0.5mm/m).
“ High performance.

I also summarise its fields of application
” Restoration of skirting boards, walls and facades.
” Walls affected by capillary rise.
” Aggressive environments with capillary rising (SR).
” Restoration mortar in old buildings.
” Exterior and interior repair of lime walls.
” Reinforcement of old lime walls with mesh.