Ventilation (known as micro-ventilation) between the tile and the supports beneath determines the tile’s efficiency and the durability of the roof across the years.
The tiles are made from natural clays, giving them a certain porosity that enables them to “breathe” by absorbing and expelling water and holding moisture inside the building. To prevent condensation and dampness that lead to leaking into the home, the tiles must be installed in accordance with the relevant standards. Good ventilation and accessories that help this process are also important.
Ventilation enables air to flow beneath the tiles and allows them to dry. It also reduces the occurrence of moss and fungi, maintaining the appearance of the roof over time. Therefore, the ridge line must never be filled with cement or similar materials. Instead, it must remain open to facilitate air flow and be fitted with protection to stop birds, insects and small rodents from entering.
Condensation occurs under a roof
Condensation occurs when the temperature falls below the dew point of the surrounding area. This process usually occurs in winter and takes place when there is a difference of more than 2°C between the temperature and the cold surface (in still air). Condensation produces water droplets when the air is concentrated beneath an open roof as the temperature drops.
This condensation can lead to dampness and a subsequent deterioration of the roof due to fungi and other organisms.
It can be prevented by proper roof installation and ventilation, which helps air flow and dries out the dampness that can appear beneath the tiles.
Tiles are made from natural clay and are therefore porous. This porosity gives the material a degree of permeability, which La Escandella controls using a process of selecting, pressing and firing the clay to remove all potential for leakage caused by the tile. Permeability, along with other characteristics of La Escandella tiles, is measured and audited periodically by various domestic and international institutions, which have awarded La Escandella tiles the most rigorous quality certifications.
As a general rule, a roof usually leaks as a result of poor tile installation (insufficient slope, excessive use of mortar, lack of ventilation, the sealing of special points such as chimneys, joins with walls, etc.), which can affect its water tightness. Each different installation requires close monitoring by a roofing professional.
Preventing mildew on the roof
Mildew, or moss as it is commonly known, is a micro-organism that appears on roofs, often due to the tiles (because of their porosity natural condition) being exposed to certain environmental conditions. These include nearby vegetation, a north-facing roof, an insufficient slope on the roof and pollution, as well as a lack of ventilation and the use of mortar.
It is almost impossible to prevent mildew because of the large range of factors that cause it to appear. However, correct dry installation, particularly avoiding the use of mortar, and the necessary micro-ventilation between the roof and its base are important factors in keeping it at bay.
We also recommend that the roof be cleaned every 3 to 5 years, depending on the home’s location and climate. This removes any residues that may have accumulated, which can prevent the tiles from drying and correctly expelling rainwater.
Preventing stains and white markings on the tiles.
White markings on tiles, known as efflorescence, appear on the tile surface due to salts or carbonates resulting from the use of too much water in mortars for installation, as well as excessive moisture and a lack of roof ventilation. The moisture is expelled by the well-ventilated areas. This water then evaporates, leaving salt deposits which cause white staining on the tiles.
Despite rigorous controls over salt levels in tiles, mortars and the water used with them can cause efflorescence. This commonly occurs during installation and can be easily countered by dampening the tiles with water and allowing them to dry (provided installation requirements have been met, particularly in relation to roof ventilation).
Where the problem occurs subsequent to installation, it must always be analyzed and treated by specialists who will not only remove the efflorescence but correct the problems causing it. Normally they will clean the area with water, and even vinegar, treating the salts and removing the surface stains. However, it is always advisable that each case be studied individually and a solution prescribed depending on the type of tile, installation and other architectural details.
Preventing the tiles from deteriorating in very salty climates
In regions prone to adverse weather conditions, particularly those close to the sea, special attention must be paid to roof installation. Good ventilation is even more important in preventing the accumulation of salts or other organisms that can deteriorate the tiles.
Micro-ventilation (between the supports and the tiles) allows the tiles to be properly ventilated, quickly drying any moisture caused by proximity to the sea, by rain, etc. and making the tiles, and ultimately the roof, more durable.
Water Blasting should only be required under special circumstances. I light mixture of moss and mold removal should be sufficient to remove green moss stains and mildew.