Old and heritage buildings are invaluable cultural assets, but they face numerous challenges that threaten their structural integrity and aesthetic appeal. Among the most significant threats are dampness, salt damage and acid rain. These factors can cause severe deterioration of building facades, leading to costly repairs and potential loss of historical value.

In dry state, salts are hard crystalline materials.

In the presence of water, salts get dissolved by water and carried into the masonry by the water flow (e.g. rainwater, rising damp etc.).

When the water evaporates the salts recrystallize, expanding 5-10 times in volume, causing salt crystallization - known as efflorescence if the salt crystallization is on the surface, or subflorescence if the salt crystallization occurs under the surface. This crystallization process creates huge pressure (up to 500 atmospheres) on the pore walls, leading to the cracking, spalling, flaking or crumbling of the masonry. Over time, many subsequent crystallization cycles can result in significant materials loss or structural damage. In addition, some salts are hygroscopic, meaning they attract moisture from the air. This can create a continuous cycle of wetting and salt crystallization, exacerbating the damage.

Acid rain is another major factor contributing to the deterioration of heritage building facades. It is primarily caused by the emission of sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) from vehicles and industrial processes. These pollutants react with water vapours in the atmosphere and form sulfuric and nitric acids, which then fall as acid rain.

When acid rain comes into contact with building materials, it can cause severe chemical weathering. Limestone and marble, commonly used in historic buildings, are particularly vulnerable. The acid reacts with the calcium carbonate (lime) in these stones, forming calcium sulphate (gypsum), which is soluble so it can easily be washed away by rainwater.

This process not only erodes the stone but also leads to the loss of intricate carvings and architectural details that are often irreplaceable.

Brick and mortar are also affected by acid rain. The acid can weakens the binding properties of lime mortars, leading to crumbling and loss of cohesion between bricks. Over time, this can compromise the structural integrity of the building, necessitating extensive restoration efforts.

To repair old facades damages by moisture, salts or acid rain, the damaged bricks or stones can be cut out and replaced by similar stones or bricks in good condition.

An alternative restoration option can be the rebuilding or repair of damaged bricks or stones with a combination of salt and acid-resistant Roman lime plaster, followed by a decorative white or coloured lime coat.

Here are the required materials for this type of repair:

1. Bentoncino Consolidante MGN consolidation plaster suitable for the rebuilding and/or mechanical consolidation of frail, damaged bricks or stones.
2. Sanacolor 2000 MGN decorative lime plaster to recreate the desired visual texture of bricks or stones. This plaster comes in 24 standard colours and virtually any decorative texture can be recreated with it.

Please see photo gallery below for examples. ALL visual-aesthetic designs below have been created using the Sanacolor 2000 MGN lime plaster by combining multiple colours and creating different textures.