Roof coatings are almost always offered as renovations for older roofs that are still intact. At the same time, there are also glazed and engobed roof tiles, which are practically factory-coated, on the market. You can read about the difference and what the technical advantages are here.
Warning of roof coatings
Subsequent roof coatings should seal roofs that are still intact and ensure greater durability.
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However, many experts warn against such work, for several reasons:
- the roof cleaning required beforehand can cause damage to the roof
- Joints between the roof tiles can be closed by the coating
- the material properties of the roof tiles are changed
- the rain protection function of the roof is changed
- Inferior, non-frost-resistant coatings can flake off
- Incorrect application can lead to irreparable damage to the roof
- In the case of a subsequent coating, the overlapping points of the roof tiles are not coated at the same time - the coating is only partially applied - this is technically disadvantageous
The counter-arguments against a roof coating are therefore diverse. In not a few cases, the roof tiles are damaged so badly by an improper coating that after a very short time there is a risk of expensive re-roofing.
Coated roof tiles
Roof tiles can either be engobed or glazed. In this way, they are provided with a comprehensive, protective coating practically at the factory.
In contrast to the subsequent coating, this protection envelops the roof tile at all points, including where the roof tiles overlap after laying.
The joints also remain intact, as the coating is applied directly to the roof tile from the start and is not applied to the entire roof afterwards.
Performance of engobes and glazed roof tiles in comparison
Conventional clay roof tiles
Even ordinary clay roof tiles have a durability of many decades. Manufacturers usually give a guarantee of up to 30 years on clay roof tiles. Even after this time, however, only punctual damage often occurs, which can be repaired by replacing individual roof tiles.
In practice, high-quality roof tiles can therefore be expected to have a service life of 50 - 60 years, and often even longer.
During production, engobes are provided with a clay slurry. The application can be done in different ways. Engobes remain strongly permeable and breathable. Different minerals or metal oxides can be added to the clay slurry.
The surface coating essentially only serves to color the clay brick, but also has certain protective properties due to the glass-like surface. So-called noble engobes are classic engobes whose clay sludge is added to glass bodies. This maintains breathability, but a protective, very hard layer covers the roof tile.
In contrast to the glaze, there are no cracks on the surface (so-called octopuses).
Glazed roof tiles
Glazed roof tiles have a high degree of gloss. The surface is covered by a very hard, glass-like layer. It is tight and prevents water from penetrating the roof tile. This will avoid some possible damage.
In the course of time, however, tensions in glazed bricks can cause slight surface cracks (cracks or claws). This weakens the protective function of the surface.
In practice, the durability of engobes and glazed bricks is not significantly higher than that of conventional clay roof tiles, but the brick has a somewhat higher protective function. Even with the roof coating, there is no conclusive indication that the roof will actually last longer; it is a purely cosmetic measure.