Tips and Tricks for Laying Natural Stone Slabs
Natural stone is very trendy and has been a popular building material for thousands of years. The number of different natural stones has increased significantly in recent years as well as the number of people laying natural stone slabs.
It demands greater specialist knowledge from the processor and planner. The assessment or the exact composition of the stone to be laid is immensely important for the final appearance.
In case of exclusive natural stones, the choice of mortar must be made with particular care so that no undesirable discolorations occur which are often irreversible and require complete dismantling.
What Is Natural Stone?
Natural stones are extracted from many different types of stone before you can lay them as natural stone slabs. They are therefore available in numerous forms, which differ in color, surface texture and also in industrial properties.
Natural stones are natural mineral aggregates which, after extraction, are physically processed - i.e., by sawing, polishing, etc. – so that they can be laid as natural stone paving stones.
Natural stones have three main groups according to their respective formation process:
The Laying Methods
In addition to mechanical anchoring, lay the natural stones in thin, medium or thick beds. The size of the rocks mainly determines the method of putting natural stones.
Calibrated natural rocks - i.e., measured, cut to size or ground slabs of precisely the same format - can be laid using the thin-bed method. These are usually panels with a thickness of 10 to 15 millimeters. It makes sense to remove the natural stone from the back with a thin layer of adhesive. It means that loose components and release agents such as dust have integration into the adhesive bed, and safe laying is guaranteed.
In the case of so-called excess lengths, use the thick-bed method.
The natural stone is also provided with adhesive slurry or natural stone adhesive on the reverse side and patted fresh in fresh into the thick-bed installation mortar. Also, there is a compensation of irregularities in the substrate in the process.
Medium-bed laying combines the advantages of thin-bed and thick-bed laying. Thus, a high area performance is achievable with natural stone slabs, and at the same time unevenness of the substrate can be leveled out.
What Causes Discoloration?
Discoloration occurs when the optical appearance of the laid natural stone no longer corresponds to the condition in which it was delivered.
Whether the discoloration is due to the carelessness of subsequent trades or the introduction of dirt, it can easily be detected. But soiling from the mortar bed can also be a trigger.
Ensure no rusting objects such as nails or crown corks. These can begin to rust and then appear as brown stains on the stone.
The interaction of moisture from the mortar bed and the stone's minerals can also lead to discoloration. In some cases, color intensification can also occur. Then the laid material appears darker than the original shade. This undesirable effect often occurs with highly porous rocks.
As a rule, these moisture spots disappear again after some time. There are various ways to prevent discoloration. Completely anhydrous systems such as epoxy resin or polyurethane, however, are expensive and often difficult to process.
Also, epoxy resins can also leave grease-like stains on some types. In preventing discoloration, use products with a high crystalline water binding capacity. With these products, the mixing water of the mortar bed is almost entirely chemically bound.
What Causes Efflorescence?
In contrast to discolorations, efflorescence occurs from the free calcium hydroxide of the mortar bed. Excess lime from the cement is transported with the moisture from the mortar bed through the stone to the surface. The chemical reaction with carbon dioxide produces calcium carbonate.
Acids are the only thing that can remove the so-called lime. Put extra care when acid-sensitive natural stones such as marble, limestone and so on are acidified.
To What Can Encapsulations be Attributed?
It is not always possible to recognize the behavior of a mineral.
In addition to discoloration, this can also lead to undesirable and irreparable encapsulation. These occur when minerals absorb mortar water and then expand more than the top of the slabs.
Apply the following rule to the risk of encapsulation: The more rectangular and thinner the natural stone, the higher the risk.
For example, slabs measuring 30 x 30 centimeters, the thickness should not be less than ten mm and for pieces measuring 30 x 60 cm, not less than 12 mm.
When the natural stone is laid outdoors, discoloration plays a minor role, as the laying materials used must always be suitable for this area of application. Damage caused by the migration of moisture with subsequent discoloration should not occur here. Under certain circumstances, installation on suitable drainage mats and systems can help.