Why should you choose quartz instead of granite?

Granite as a floor covering in the outdoor area: You should pay attention to that

Granite is a very noble-looking, robust floor covering for outdoor use. However, there are always problems with the joints between the individual panels. We explain why in this article.

Granite is a very high quality floor covering: it is extremely robust and almost indestructible. Neither water nor frost can harm it. In addition, granite is a comparatively inexpensive natural stone that is available in a variety of colors and patterns. Granite slabs are therefore the perfect way to give the terrace a classy look for little money.

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What is real granite?

Granite is a so-called "igneous" rock that - originally liquid - was formed by solidification at great depths in the earth's crust. The molten rock does not have the same composition everywhere; the main proportions of feldspar, quartz and mica are represented in different proportions. There are also clays, which give the stone a special color. The main parts of the mixture are individually crystallized and easily recognizable with the naked eye.

There are large numbers of granite deposits throughout the world. All types of granite extracted there have a different composition, which determines the properties and appearance. "Hard as granite" is a common term. Due to the different composition - depending on the occurrence - you have to assume that not all varieties have the same properties.

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There are very hard and less hard, persistent and less persistent varieties. To make matters worse, according to US and Chinese standards, rocks such as basalt, diabase and others are also referred to as granite ("granite"). If you want to be sure that you are getting "real granite", then you should make sure that the product complies with the European standard EN 12440.

As a rule, real granite cannot soak up liquids. It is absolutely tight and largely pore-free and resistant to all cleaning agents used in the household. As mentioned above, there are natural stone slabs on the market that are known as granite and look similar but have a different composition. These products are not always as resistant as "real" granite.

Grouting granite

Granite slabs are frost-proof, wear-resistant, robust, resistant to road salt and acids. However, many owners of granite terraces or granite stairs outdoors have problems with the joints between the granite slabs over time.

The durability of joints in outdoor coverings mainly depends on three factors:

1. Expansion and shrinkage behavior of the building materials used in hot or cold conditions
2. Grout mortar / compound
3. Type of covering

Different expansion behavior of granite slabs and grout

All building materials expand when it is warm and contract when it is cold. This expansion and shrinkage behavior is very different depending on the material and composition, sometimes more, sometimes less. The change in dimension is referred to as the coefficient of expansion (AK). While the AK is always the same for industrially manufactured materials such as steel, it can be different for tiles, concrete slabs, porcelain stoneware slabs, plaster and mortar. In the case of building materials made of natural stone such as granite, differences in the AK can also occur depending on the origin.

If the listed materials are used outdoors, for example as a covering for balconies or terraces, temperature differences of +60 degrees Celsius to -20 degrees Celsius can occur. This means that the covering and grout must be able to cope with temperature differences of 80 degrees Celsius.

Due to the large number of damaged balcony and terrace floors, it must be assumed that the expansion and shrinkage behavior, the AK, of the covering and the grout is different. As a result, fine hairline cracks form in the border area between the covering and the grout. According to the capillary law, these hairline cracks pull in water very deeply, the finer the crack, the deeper. When the water freezes in the fine cracks in winter, its volume increases considerably. The ice that forms unfolds an enormous explosive force and drives the hairline cracks apart. The water can penetrate even deeper, and the development described continues. The result: first the joints break open, later the covering flakes off.

This development is further promoted by a possibly insufficient gradient (less than two percent). If rain and melt water cannot run off immediately, waterlogging forms, which can quickly penetrate the joints.

Weak point border area between granite slab and mortar

Grout or grout are offered as "frost-resistant". This property is achieved through a high proportion of cement and a "plastic coating". This means that the mortar dries through without pores. There are no capillaries into which water can penetrate. Nevertheless, joints can tear in the border area between the covering and the mortar, especially if there are adhesion problems on the edges of the covering. There are cement-trass mortars that may have a cheaper shelf life than grout.

In the case of house demolitions or renovations, one can observe that the adhesion of masonry mortar to the bricks varies considerably. There are bricks within a wall from which the mortar flakes off without leaving any residue, while there are other stones from which the mortar can only be removed with force. The reason for this is the different porosity of the brick surface. The more "open" the brick, the greater the adhesion of the mortar. The more porous the edges of the coverings, the better the adhesion of the grout. Granite, however, has almost no pores. Therefore, grout does not adhere well to the panels. The result: water penetrates.

Joints between granite slabs must be renewed regularly

It will be difficult to achieve permanent grouting of granite paving. Anyone who opts for a granite terrace will have to put up with having to renew the joints regularly.

If you want to lay the granite slabs yourself, read here what to look out for when laying slabs on the terrace. And we will tell you about the advantages and disadvantages of stone as an indoor flooring.