Although tiles are generally considered to be virtually waterproof, they do not protect against water damage. And it is not only unpleasant, but can also be expensive and even dangerous. In this article you will learn what causes moisture under tiles, how to find a wet spot and how best to eliminate the problem.

Risk factor moisture

In principle, moisture in buildings is not a bad thing, in fact it is important. In the air, it contributes to a pleasant indoor climate and almost all building materials and materials only retain their stability permanently through the regular absorption of water or water vapour. However, only as long as the humidity remains within limits.

Too much moisture under tiles can sooner or later lead to water damage – and thus inevitably to a rat tail of negative consequences. These affect not so much the tile itself as the substrate on which they are laid. So musty smelling rooms and dark spots or salt efflorescence on the wall are the lesser evil. It is far more serious if the damage already affects the entire floor structure or the entire masonry, and if mould which is a health hazard has already formed on it. Because in these cases a complex and expensive complete renovation is usually no longer to be prevented.

Possible causes for water damage under tiles

Basically, water damage under tiles can occur in two ways:

  1. Because moisture is trapped under the tile covering, or
  2. Because water comes in from above.

For the former, improper tiling is usually responsible. For example, if tiles are laid on a floor structure that is not sufficiently dry or if there is so-called subsequent moisture from the substrate after laying. In these cases, moisture remains permanently under the tiles and can cause damage to the entire floor structure. For this reason, especially with freshly laid screed, it is important to check the readiness for laying by determining the residual moisture before starting to lay the tiles. Particularly in the case of large-format tiles with a low proportion of joints, it also sometimes happens that the moisture cannot escape sufficiently from the jointing mortar or tile adhesive and thus also remains under the covering.

The second cause of water damage is that wetness only gets over the surface and under the tiles afterwards. Whether it is due to acute exposure to water, such as flooding, burst pipes or the leaking washing machine, or due to regular exposure of the tiles to moisture, such as the steam in the shower or bathroom. However, the moisture does not penetrate through the tile itself, as the material hardly absorbs any water, but through the joints. Regardless of which filling material is used, joints are always water-permeable – even joints sealed with silicone can become brittle or perforated over time and thus lose their seal.

So the crux of the matter is: under tiles, water damage usually goes unnoticed for a long time. The coating probably covers the affected area so that the water can spread unhindered. And even if damage is then already apparent, the actual extent is usually still hidden under the tiles.

This makes it all the more important to start looking for the cause at the slightest suspicion or at the latest at the first signs and to obtain certainty by determining the moisture content under the tiles.

Measuring moisture: How it works

There are various possibilities for measuring moisture under tiles, which differ in effort and significance:

Direct procedures

In direct methods, such as the calcium carbide (CM) method known for determining the residual moisture of screeds, a sample is taken from the building material, crushed and mixed with calcium carbide in a pressure bottle. Based on the chemical reaction, the moisture content can then be determined using a manometer. This method is considered to be particularly reliable – and incidentally, it is also the only one recognised by the courts – but it is also the most complex and can only be carried out by a specialist.

Indirect methods

Indirect moisture analysis using moisture analyzers, on the other hand, is much simpler and therefore basically also practicable for private use. Numerous tile manufacturers offer a wide variety of models, most of which are already available at relatively low prices. Depending on the type and design, these devices can usually be used to measure floor or wall moisture even through tiles or other surfaces.

In principle, two variants are common for this:

Capacitive measurement

With the capacitive method, the moisture meter generates an electrical stray field in the sensor head, via whose permeability the moisture content at the respective location is determined at a depth of approx. 3 cm. The advantage of this method is that it is completely non-destructive and can be repeated as often as desired. The disadvantage is the relatively small measuring depth, which means that the results may not be reliable enough in the event of deeper water damage. In addition, a certain amount of expertise is advantageous for the correct interpretation of the measured values, as these can be influenced by salts or metals in the building materials.

Resistance measurement

In electronic measurement according to the resistance principle, current is conducted via electrodes into the presumably moist area. The conductivity of the material then provides information about the moisture it contains. The higher the resistance, the lower the measurement result and thus the moisture content. The advantages and disadvantages of such a moisture meter: the wall or floor must be drilled at the affected area in order to be able to insert the electrodes, but it is also possible to detect deeper water damage. Alternatively, however, it is usually possible to measure over joints.

Nevertheless, caution is generally advised when searching for water damage on your own. Since the results are determined differently for each measuring instrument and are displayed according to manufacturer-dependent scales, there are no general standard values. In order to obtain really reliable information about the moisture content, it is therefore always advisable to consult a professional.

Water damage – what now?

If water damage is detected, there is definitely a need for action. Whether it is sufficient to dry the affected areas sufficiently and eliminate the cause (e.g. renew leaking silicone joints in the bathroom) or whether major renovations are already necessary, however, again only an expert can judge. If the wrong measures are taken, the damage can sometimes be even worse.

Tiles and underfloor heating have one thing in common: both offer building owners numerous advantages in terms of living comfort and therefore form an ideal combination. Nevertheless, the topic repeatedly raises uncertainties and questions in the run-up to the event. You will find the most important answers in this article.

Which floor covering is best suited for underfloor heating?

Whether tiles or stone, parquet or laminate, vinyl or carpet – anyone who wants cosy warmth without radiators can in principle draw on the full range. In principle, any floor covering can be laid on underfloor heating.

The difference, however, is how quickly the heat from the underfloor heating system is transferred to the floor, or what flow temperature is necessary (and possible) to control the room temperature as desired. In other words, the different materials differ in their thermal conductivity. This in turn has an impact on energy efficiency and thus ultimately on heating costs.

This is precisely why tiles are the best choice for underfloor heating. Due to their dense surface, they score points with a very high thermal conductivity between 2.3 and 2.8, which is about 5 times higher than, for example, underfloor heating under hardwood flooring or underfloor heating under vinyl flooring. In addition, the heat is stored in the tiles, which means that the floor not only heats up quickly, but also stays warm for a long time – thus saving additional energy.

Can all tiles be used in combination with underfloor heating?

There are essentially no restrictions when using tiles on underfloor heating. Both natural stone and stoneware and porcelain stoneware are equally suitable for underfloor heating. To achieve the most efficient heating result, tiles with a maximum thickness of 20 mm are recommended. Thicker coverings are also possible, but the heating time may increase slightly.

Regardless of the heating system, when selecting the floor tiles, attention should also be paid to the abrasion group of the tiles and the anti-slip class of the tiles. This ensures that the floor meets the requirements of the respective area of application in the best possible way.

What surface temperature can tiles for underfloor heating withstand?

A great advantage of tiles is that they can withstand even high temperatures without damage. In contrast to many other floor coverings, they can therefore be heated to a surface temperature of 29°C and more without any concerns. This results not least in the high heat output of up to 200W/m2 with simultaneously low energy consumption.

Tiles on tiles & floor heating – is that possible?

Particularly in the case of renovations, the question often arises as to whether the new tiles can be laid on top of the existing tile covering. The answer to this is quite clear: Yes, on underfloor heating this is no problem. The combination of tile on tile – underfloor heating works perfectly and without affecting the heating result: Due to the extremely high thermal conductivity of the tiles and the correct tile adhesive as an additional heat conductor, the heat of the underfloor heating is transferred from layer to layer without loss.

Only condition: The old flooring must be perfectly laid and intact and in the spatial conditions the higher floor construction must not cause any problems (e.g. stripes of doors etc.).

What should be observed when laying tiles on underfloor heating?

Although tiles and underfloor heating harmonise perfectly, there are a number of points to consider before and during installation to prevent any difficulties from the outset.

Type of underfloor heating

There are basically two options for underfloor heating: They can be operated either with water or with electricity to generate heat. In principle, both water-guided and electric underfloor heating can be installed under tiles. Which heating system is most suitable depends rather on the respective application.

Warm water underfloor heating systems work via plastic or copper pipes, which are inserted into the screed as a wet or dry system and through which heated water circulates. Because the installation effort is relatively large and a certain installation height is also necessary, hot water underfloor heating systems are primarily used in new buildings.

In contrast, with electric underfloor heating systems thin heating mats ensure the correct room temperature. These can also be laid on the screed at a later date with relatively little effort and require a lower installation height. They are therefore also suitable for the renovation of existing buildings or can be retrofitted as a supplementary heating system in rooms with high heat loss (e.g. conservatories).

Condition of the substrate

An optimal substrate is the basic prerequisite for a durable and flawless tiled floor. Therefore, tiles should not only be laid on a substrate that is as smooth as possible, but especially on a completely dry substrate. Because too much moisture under the tiles can otherwise sometimes cause the tiles to come off or other damage later.

Particularly when laying on newly erected and wet laid heating screeds, care must therefore be taken to ensure that they are ready for laying. Normally, a screed needs about 4 weeks to harden completely – in the meantime, however, special quick binders are increasingly used to accelerate the process. In general, it is advisable to heat the screed in a controlled and gradual manner using underfloor heating. On the one hand, the drying phase can be shortened and, on the other hand, both the heating and the screed can be checked for function and condition.

The screed is finally ready for laying the tiles when the residual moisture determined by means of a suitable measuring method (e.g. CM method) has fallen below a certain limit. As a guideline, a maximum of 2 % for cement screeds and a maximum of 0.3 % for calcium sulphate screeds are to be taken into account, whereby the laying instructions of the manufacturer are to be observed for the exact values.

Protection against moisture

In principle, tiles can be laid directly on the screed. However, in order to protect the substrate from penetrating moisture from the tile adhesive, it is recommended to apply a sealing primer or tile primer before laying. Otherwise, there is a risk that the screed will soften and the flooring will no longer adhere properly.

Suitable tile adhesive and tile mortar

Although underfloor heating generally heats tiles very evenly and constantly, temperature fluctuations still occur. This leads to slight expansion of the material and corresponding stresses on the surface. To compensate for these movements – and thus prevent stress-induced cracks in the tiles – highly flexible and temperature-resistant materials should therefore be used as tile adhesives or tile mortars. In some cases, a decoupling mat can also be laid under the tiles.

During installation, care should also be taken to ensure that these are applied over as much of the surface as possible. This allows the tile and adhesive to bond better, which is particularly advantageous in the case of surface tension. And besides, the heat transfer is additionally optimized.

Expansion joints

A no less important aspect in connection with the temperature-related expansion of the materials is the interaction expansion joint – tiles – underfloor heating.

Expansion joints should be taken into account, especially in edge areas, and should allow for a minimum of 5 mm room for movement. In addition, it is essential to create additional expansion joints in those places where the screed also has them. Otherwise, the tile and substrate may expand differently, which may lead to cracks or fractures.

When can the underfloor heating be put into operation after tiling?

A freshly tiled and grouted floor must not be heated up immediately. This could cause the adhesive and joint sealant to dry too quickly and become brittle. The general recommendation is to wait about 28 days until the underfloor heating is activated. The temperature should then be increased continuously in 5-degree steps over a period of several days until the desired flow temperature is reached.

They have already become the standard for professional tilers – and the use of decoupling mats definitely has advantages for do-it-yourselfers too. Because by decoupling from the subfloor, consequential damage during tile installation can be reliably prevented. In this article you can read about when a decoupling mat makes sense, what functions it fulfils and how best to lay tiles decoupled.

Why do you need decoupling mats at all?

Tiles are extremely popular as floor coverings: they score points with their attractive appearance, are robust and hard-wearing – and are in principle suitable for laying on almost any surface. In principle, it is quite common to bond tiles directly to the screed, but it is often advisable to lay them separately. The reason for this is as simple as it is serious:

As building materials expand and contract again with temperature fluctuations or moisture, movements in the soil inevitably occur. But the crux of the matter is that the elongation behaviour is different for every material. Thus, tiles usually react differently to changing conditions than the underlying floor. If there is a rigid connection to the ground, this can quickly have unpleasant consequences. Although the movements are usually only fractions of a millimetre, the resulting stresses are sufficient to cause cracks or fissures in the tiles. Such damage can be prevented with decoupling mats. This is because they provide the necessary scope for the materials to expand independently in all directions.

What is a decoupling mat?

As the name suggests, a decoupling mat decouples the covering from the floor. This means that the mat forms an additional flexible separating layer between tiles and substrate. Since there is no longer a direct connection, movements, tensions or vibrations are no longer transmitted from the substrate to the tiles. The decoupling mat absorbs them completely or at least minimizes them so that no cracks can develop.

Where should a tile decoupling mat be used?

To be on the safe side, there is no harm in principle in laying tiles decoupled. However, in some cases it is particularly important. First and foremost, this concerns the laying of tiles on critical or vibrating surfaces. In other words, wherever the risk of stress-related damage is particularly high or where unevenness and cracks in the substrate have to be compensated.

Freshly laid screed, for example, tends to crack when drying, which can be bridged by a decoupling mat. Decoupling mats are also obligatory when laying tiles on an existing wooden floor. This is because the latter generally reacts to external influences, such as temperature or humidity, with stronger expansion behaviour.

But even if large areas and/or large-format tiles are bonded, above-average stresses can occur overall. The same applies to spot or weather-related temperature fluctuations when tiles are laid, for example, on underfloor heating systems or in outdoor areas. In addition, decoupling mats are also highly recommended for particularly high loads (e.g. in garages) in order to provide the necessary protection against cracks or breakage.

In addition, a decoupling mat improves the adhesion of the tiles, making it possible to lay them on poorly adhering subfloors. For this reason, for example, decoupled installation should also be preferred on floors with existing layers of adhesive, varnish or paint.

ACHTUNG: However, with particularly flexible substrates (e.g. if the rafter spacing in the substructure is too wide), decoupling mats sometimes reach their limits. In this case, it is recommended to first lay plasterboard or OSB boards and only then to attach the decoupling matting.

What types of decoupling mats are available?

Various manufacturers offer decoupling mats in various designs and materials. Most common are products made of plastic, rigid foam or textile fibres, which are usually available as yard ware on rolls in specialist tile shops or DIY stores.

What all commercially available decoupling mats have in principle in common is their multi-layer structure. While the flexible core of the mat ensures the described equalization of tensions and movements, the mostly nubbed outer layer is used for fixing to the substrate on one side and the tile covering on the other side. In addition, ventilation ducts are often installed on the underside, allowing moisture to escape from the respective substrate even after the tiles have been laid.

In principle, modern decoupling systems are therefore suitable for almost any difficult substrate, such as concrete, mixed subfloors, wooden floorboards, chipboard, cement or dry screed, old tiles and many more. Which decoupling mat is best in a specific case, however, depends on the respective area of application and the associated requirements. This is because in addition to the actual function of decoupling, most mats also have other advantages.

Textile mats in particular, such as a PCI decoupling mat, are characterised by improved footfall sound insulation. While other systems, such as Schlüter Ditra decoupling mats, are universally applicable at all, as they combine multifunctional properties in one product with decoupling, sealing, vapour pressure compensation and drainage.

How are decoupling mats installed?

Laying decoupling mats is easier than you might think, but there are a few things to consider.

In principle, decoupling mats can either be glued over the entire surface or laid as a floating installation, whereby the former is more common in practice. However, the method to be used for the respective product always depends on the manufacturer’s recommendations.

Nevertheless, the procedure for both installation techniques is almost identical and essentially consists of the following steps:

Step 1: Prepare the substrate

Regardless of whether the decoupling mat is to be laid floating or glued, the subfloor must be clean, level and load-bearing. For highly absorbent substrates, a primer or a tile primer may also be useful.

Step 2: Measuring and cutting the mats

Before laying, the spatial conditions are measured and the mats are cut to size accordingly. In order to avoid unnecessary waste, special care should be taken – even a laying plan can sometimes be helpful. To avoid sound bridges, insulation strips should also be used in the edge areas.

Step 3: Attach decoupling mat

With floating installation, the decoupling mat is only loosely applied to the substrate. For full-surface bonding, the mat is fixed with highly flexible tile adhesive (marking C2). It should be noted that the adhesive hardens very quickly. Therefore, only as much should be applied as can be covered with the decoupling mat within a few minutes.

Step 4: Sealing the joints

Although decoupling mats are waterproof on the surface, water can still get into the ground at the joints. Therefore, an appropriate sealing of the latter is necessary. Usually sealing tapes are used to prevent the penetration of moisture under the tiles.

Step 5: Laying tiles

The decoupled subfloor is then ready, on which the tiles can be laid in the usual way using flexible tile adhesive.

What does decoupling cost?

Finally, a few words about the costs of decoupling mats:

Basically, of course, the material requirement is decisive due to the number of square meters of the area to be decoupled. In the end, however, the materials used as well as the quality and functionality of the selected mat, but also the manufacturer, are decisive for the actual price. Standard mats are available for just a few euros per square metre, while particularly high-quality products are happy to make a multiple of that. On average, a realistic calculation can be made at around 10 euros per square metre, plus the cost of the flexible tile adhesive. All in all, decoupling mats are therefore not exactly cheap. With regard to a durable and above all damage-free tiled floor, the investment is definitely worthwhile.

If you want tiles, you also need joints – and therefore sooner or later you have to find the right grout. Compared to the tiles themselves, the choice is much less extensive, but the decision is no less important. Read this article to find out what types of grout are available and how to choose the right product for your tile project at home.

The tasks of joints

There are two main reasons why grouting tiles is so important: one visual and one technical. On the one hand, joints set design accents and give wall or floor tiles their final, characteristic appearance. On the other hand, they compensate for movements of the tiles or the substrate, distribute acting forces, prevent the penetration of moisture under the tiles and ensure a hygienically closed surface. In other words: joints take over several central functions for a durable, flawless, robust and hard-wearing tile covering.

However, the decisive factor is to find the right grout for the tiles used, the existing substrate and the degree of stress in the respective area of application. After all, not every grout is equally suitable for the different requirements in terms of durability, use and load of the tiles.

What kind of grout is available?

A large number of different grouts are available in stationary specialist shops, DIY stores or online. Apart from brand and price, these differ primarily in their composition. Depending on the raw material base, jointing mortars are divided into the following categories:

Normal joint mortar / cement joints / joint white

The classic joint mortar – commonly referred to as joint white – consists of fine cement, colour pigments and fillers without a plastic content. Simple joints in tiles or slabs can usually be produced without problems and at a reasonable price with this type of grout.

However, it should be noted that the material does not guarantee water-repellent joints, which means that conventional cement grout is not recommended for tiles in damp or wet rooms . In addition, the grout made of conventional, cement-based tile mortar is relatively rigid and should therefore only be used on flexurally rigid and thus vibration-free substrates.

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Flexible joint mortar / Polymer-modified cement joint / Flex joint

In principle, flexible joints are also cement grouts – but enriched with plastics. These make the grout more elastic, so that material movements and surface tensions (e.g. with vibrating substrates or temperature fluctuations) of the tiles can be compensated. In addition, flex joints are usually water-repellent and improve the tile’s flank adhesion.

This means that jointing compounds made of polymer-modified cement can be used in a variety of ways and also for more demanding applications. The areas of application range from wall and floor tiles subject to higher loads to tiles on underfloor heating systems and other problematic substrates to patio tiles or tiles in rooms subject to splashing water or wetness, such as bathrooms or showers.

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Rapid jointing mortar

Wherever newly laid tiles need to be reused quickly, fast grouting mortars are often used. These grouts set within a few hours and are then both waterproof and frost-proof (partly suitable for tiles in outdoor areas). In addition, fast-setting grouts can be washed off the tiles earlier and at the same time longer, which is particularly advantageous when grouting large areas. As a rule, this type of grout is mainly used in the commercial sector, less so for private individuals at home.

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High strength jointing mortar

If tiles are exposed to heavy loads, high-strength grouts are recommended. The extra-fine microcement jointing compound hardens particularly densely, then exhibits a very high abrasion resistance and is even resistant to weak acids.

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Epoxy resin jointing mortar

Where even the best cement grout is no longer sufficient, expoxy resin grouts are used. They are diffusion-tight, resistant to chemicals, easy to clean (important for clean tiles with tile cleaner) and extremely hard-wearing. The solvent-free two-component joint sealants are therefore often used on complicated substrates or in wet areas exposed to water, such as swimming pools, wellness areas, commercial kitchens, laboratories, etc.

However, all these advantages are counterbalanced by disadvantages – first and foremost the elaborate processing and the higher price. But even the completely vapour-tight surface can become a problem if penetrated moisture under the tiles can no longer escape.

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Grout colours: What works how?

As mentioned at the beginning, besides the functional benefit, the optical effect of joints should not be disregarded. Especially the colour play of grout – tiles can make a room look completely different. For example, a surface is generally considered to be much more harmonious when tiles and grout are colourful tone on tone, while strong contrasts are often used as a conscious element of interior design.

This should definitely be taken into account when deciding on a suitable grout. However, the colour sorting of many tile manufacturers is unfortunately not always very varied – most articles are offered in various gradations of the classics white and grey, with more and more alternatives being offered online in particular.

Even ambitious craftsmen know: tiling is not that easy. It requires craftsmanship, experience and precise execution. Otherwise, mistakes can quickly happen that cannot be easily eradicated. So if you don’t think you can do it yourself, you should probably leave the laying to a professional. The decisive question in this context is then quickly: What will the tiler cost me? The answer to this question is revealed in this article.

What are the costs of tiling?

One thing in advance: It is not easy to give a general answer to the question of how much the laying of tiles by a professional actually costs. This is because the tiler price depends on several factors and can therefore vary greatly depending on the project.

What the tiling will cost is always influenced by the following three components:

  • Material
    • which tile manufacturer
  • Workload
  • possible additional services
    • must the substrate first be levelled with a leveling system for tiles?
    • must the substrate be levelled with a levelling compound for tiles?

These costs are usually quoted per square metre, which is also the most reliable basis of calculation for you as a customer. This allows you to estimate the total cost of tiling a given area when you request a quotation.

Material costs

The tiles themselves naturally account for the largest share of the material costs. The following applies: the price differences are just as large as the selection. While simple ceramic floor tiles or promotional items are already available from 5 to 10 euros per square metre, extravagant brand-name tiles or special formats, such as mosaic tiles, for example, can also be considerably more expensive at 70 to 100 euros per square metre. On average, however, high-quality tiles usually cost between 20 and 40 euros per m2. When making your choice, make sure that the tile is suitable for the desired application. You should pay particular attention to the tile abrasion class and in the bathroom or on the terrace additionally to the skid resistance of the tiles. This may increase the costs a little bit, but the higher quality is definitely worth it in these cases.

In addition, there is also the tile mortar or tile adhesive during laying or the grout. Depending on the size of the tiles, joint width and the filling material used for the expansion joints of the tiles, the costs per m 2 for this can be between 2 euros and 11 euros.

The total cost of the material depends, of course, on the surface on which you want to lay the tiles. Because on the one hand, this determines how many square metres of tiles you need, and on the other hand, what tile mortar or adhesive is required.

You can easily calculate a guide value for the material requirements:

For a floor installation, multiply the length and width of the room, for wall tiles take instead the height up to which the tiles should be placed. Also remember to allow for about 10 percent reserve for cuttings, breakage or later repairs.

Labour costs

The choice of tiles also influences how much the laying work costs. This is because tilers calculate the estimated work required with the corresponding tile and also convert this into costs per m2. In addition to the cost of laying tiles, the prices quoted per m 2 usually also include grouting and other necessary sealing work (e.g. silicone or acrylic joints). If not, this usually adds about 1 to 2 euros per meter.

The price per square meter is influenced by several factors:

Thus, floor plans that require complex cutting of the tiles increase costs just as much as special requests or complicated patterns. In addition, glued installation is in principle cheaper than laying tiles in a mortar bed. On the one hand, even large-format tiles often mean less work and correspondingly lower costs because they can be laid more quickly. On the other hand, however, they must also be aligned much more precisely, which at the same time increases the effort required. The trend towards particularly narrow joints, often associated with large tiles, can also increase costs.

As a rule, the cost of a tiler is between 30 euros and 50 euros per m 2. However, the above-mentioned influencing factors can by all means increase the costs per m 2 by another 10 to 20 euros. In addition, regional price differences may exist: For example, tiles are generally more expensive to lay in the city than in the countryside – and the well-known West-East divide also plays a role.

Some tilers prefer, especially for complicated orders, to charge according to actual time spent instead of a price per m 2. An example of this is the laying of tiles on stairs, as the amount of work involved here is above average in relation to the area. An hourly rate of at least 40 euros is normally customary in the industry, but the costs can sometimes be considerably higher depending on the requirements or qualifications of the tilers.

Additional services

In addition to material and installation work, additional costs may also be incurred. For example, you should check whether the offer already includes the filling and priming of the surface. This is because this work is required relatively frequently and can also cost around 5 euros per square metre extra. Also the installation of edge or skirting boards usually costs around 5 euros per meter extra. Not to be forgotten are possible costs for travel, construction site equipment or transport or delivery of the tiles.

Example: Costs for 20 square meters of tiles

On the basis of the cost factors for tiling, which have now been explained, the following exemplary calculation now shows what a tiler can cost for 20 m2 :

  • Tiles (porcelain stoneware, abrasion class 2, non-slip, EUR 30,-/m2) 600,- Euro
  • Tile adhesive (permanently elastic, EUR 7,-/m2) 140,- Euro
  • Filling and priming (extra charge, EUR 5,-/m2) 100,- Euro
  • Labour costs for tilers (EUR 40,-/m2) 800,- Euro
  • Additional services (installing skirting boards, setting silicone joints) 150,- Euro
  • Journey all-inclusive 70,- Euro

Total for 20 m2 Have tiles laid 1,860.- Euro

The best saving tips when tiling

All in all, it can be quite expensive to hire a tiler. Therefore we have a few tips on how you can reduce costs:

  1. It pays to compare prices
  2. You can also save on the installation itself, for example by dispensing with elaborate installation patterns or by not selecting a joint width that is too small.
  3. Avoid billing on an hourly rate to avoid unforeseeable cost developments. Instead, it is better to agree on a flat rate if a price per square metre is not possible.
  4. In addition, you can already make some advance payments yourself, which the tiler would otherwise charge for. For example, you can prepare the substrate by cleaning, smoothing and priming it yourself.
  5. You can also do the grouting or sealing with silicone yourself. Compared to tiling itself, this is almost child’s play.

Tiles convince not only by their attractive appearance and durability, but above all by their durability. Optimum adhesion to the substrate is the be-all and end-all – and for this you need the right conditions. In this article, you will learn how to ensure that your tiles have a lasting hold and what a decisive role the primer plays in this context.

The right substrate for tiles

Whether cement, concrete, plaster or even tile on tile in the bathroom – in principle, you can lay tiles on almost any surface. The prerequisite, however, is that they are clean, dry, flat and stable.

For example, when laying a new screed, it is essential to allow time for the tiles to fall below a certain residual moisture content and for the floor to be ready for laying. While, on the other hand, when laying tiles on top of tiles, you must first create a sufficiently even surface – preferably by using tile levelling compound, which you use to cover the old tiles.

But that’s not all. Because in most cases, an optimally prepared substrate also includes the right primer.

Primer – why actually?

If we were to ask you what actually makes tiles stick, tile adhesive would probably be your first answer. Basically, this is not wrong of course – after all, you can use it to attach the tiles to the wall or floor. But then it is not quite right either. Because the adhesive alone does not provide good adhesion.

In order to ensure that the tiles actually remain permanently bonded, you must first ensure that the substrate is evenly absorbent to increase the effect of the tile adhesive or even create it in the first place. And that is exactly what the primer is for.

Which primer for which substrate?

In principle, a distinction is made between the categories of deep primer and adhesive primer. The various products, which are available in a wide range of ready-to-use products in specialist shops, differ both in their composition and in the type of surface on which they can be applied:

Deep base for highly absorbent material

Highly absorbent substrates, such as plaster or cement, draw water from the tile adhesive – with potentially unpleasant consequences during and after installation. On the one hand, the adhesive hardens faster, leaving you less time to install the wall or floor tiles. On the other hand, the adhesive effect can be impaired, which in turn leads to less adhesion of the tiles. In these cases, therefore, a pre-treatment with Tiefengrund forms the basis for a permanently perfect result when tiling.

Tiefengrund is usually a liquid primer based on synthetic resin, which is applied to the substrate diluted with water or undiluted, depending on the manufacturer’s information. It penetrates deep into the surface, solidifies the material and thus reduces its absorbency. In this way, the primer not only helps the tiles to adhere better, but also protects against too much penetrating moisture under the tiles.

Primer for smooth surfaces

In contrast, primer is used on non-absorbent or only weakly absorbent, smooth surfaces on which bonded tiles would normally not hold sufficiently.

This type of primer provides optimal conditions, especially for surfaces made of concrete, metal or even screeds made of mastic asphalt. In addition, existing tiles can also be treated with primer to ensure the necessary adhesion when laying tile on tile.

Adhesion primer consists of coarse-grained mortar with binding agents, which serves as a bonding agent between tile and adhesive. Unlike Tiefengrund, Haftgrund does not penetrate very deeply into the surface.

The best tips for an optimal primer

1. determine the absorbency of the substrate

Before priming your wall or floor, you should first test the absorbency of your substrate. With the so-called scratch test this can be tested well and easily: The easier and deeper you can prick the surface with a screwdriver or other sharp object, the more absorbent it is.

Another possibility is the water test, in which you moisten a small area of the substrate. If a dark discoloration is visible, you are also dealing with a highly absorbent material.

2. choose a suitable primer

On the shelves of DIY stores, but also in various online shops, you will find countless different products for priming. You can find out which of these is the right one for the condition of your surface from the manufacturer’s information. In addition, the primer and adhesive must be compatible. Ideally, therefore, only products of a system should end up in your shopping cart.

3. apply primer step by step

Before the primer can be applied, dust, dirt and material residues must be carefully removed from floors or walls. For the priming itself, it is best to use a paint roller or ceiling brush to achieve the most even result. Alternatively, you can also use a brush or a spray bottle.

In case of highly absorbent surfaces or larger damages, it is recommended to apply at least two coats of primer (first diluted and then undiluted) – more if necessary. Make sure that the first layer is sufficiently dry before applying the next one. All necessary information about the drying time can be found in the manufacturer’s instructions. When the primer is dry, you can start laying the tiles.

Expansion joints is the decisive keyword for a permanently beautiful and damage-free tiled floor. After all, like almost any other material, tiles need sufficient room to move to be able to work. In this article you can read about the important functions of an expansion joint, where it is required and how best to create it.

Why do you need expansion joints?

Tiles consist mainly of natural raw materials that react to external influences. Temperature fluctuations or the application of force cause the plates to work: The material expands and contracts according to the ambient conditions. However, this reaction behaviour is not a unique phenomenon of the tile, but occurs always and everywhere where different building and material materials meet.

This is exactly the point why expansion joints are so important when laying tiles. They serve as a buffer to compensate for the movements of the different materials without the components colliding with each other. At the same time, expansion joints have another function: they dampen sound because they reduce the transmission of vibrations.

What happens if the expansion joint is missing?

As low as the expansion and shrinkage behaviour of tiles may be, it can be unpleasant if expansion joints are not taken into account accordingly. Although the changes are usually barely perceptible to the human eye, they do increase the pressure on the individual plates.

This causes stresses on the surface, which in turn can cause cracks in the tiles. And sometimes not even directly where the joint is missing, but – due to the transmission of force – in a completely different place. Therefore even adjacent floor coverings or the screed can be damaged if the corresponding joints are not set.

For which tiles are expansion joints necessary?

Expansion joints – often also called movement joints, expansion joints or dilatation joints – are to be considered in principle for all tile floors. No matter whether it is natural stone, earthenware, stoneware or porcelain stoneware. Also the substrate or the tile adhesive or tile bonding primer used during installation have no influence on the necessity of the joints.

Where should an expansion joint be placed?

Specifically, expansion joints must always be created when different components come together. This primarily concerns all transitions to rooms (e.g. door thresholds) and between different floor coverings (e.g. B. tiles and parquet), but also areas which are only partially tiled (e.g. around a tiled stove or fireplace) or which adjoin rigid elements (e.g. radiators or fittings).

Edge joints as a connection area to the wall are also considered expansion joints and must therefore always be taken into account accordingly. In addition to their compensatory function when expanding, they also ensure that the impact sound is not transmitted to the wall and thus into the room. This is one of the reasons why they should be regularly maintained and checked for their condition or tightness (to protect against moisture under the tiles).

Important: Interaction of expansion joint & observe screed!

Existing expansion joints from the screed must also be taken over in the tiled floor – and in the same position. This applies both to the initial laying of tiles and slabs and to subsequent renovations. Only then can it be guaranteed that the substrate also has sufficient room to move and that the materials can work independently of each other according to their properties. This avoids cracks or fractures that could otherwise sooner or later be transferred to the tiles. Where these joints should be planned exactly is usually announced by the screed layer.

By the way: A term that also appears again and again in connection with the screed are the so-called dummy joints. Although these serve a similar purpose to expansion joints, they are not actually expansion joints. Rather, these are deliberately placed predetermined breaking points that specifically control the further course of possible cracks in the screed.

From which room size are expansion joints required?

The formation of expansion joints is regulated according to DIN standards. Accordingly, field boundary joints are prescribed for rooms with a size of 40 m2, whereby the field length and width should be between 5 and 8 m at the most. In this context, the room geometry, the tile format used and the expected stress on the floor must be taken into account. If the room has a floor heating under the tiles, the arrangement of the heating circuits must also be taken into account.

In general, the recommendation is to work in expansion joints vertically and horizontally at intervals of 3 to 6 m. For larger areas and tiles in outdoor areas, joints should be planned around every 4 m, as the expansion of the tiles can be even greater there than indoors due to higher temperature differences.

How wide must an expansion joint be?

The width of the joints depends on the tile format as well as on the respective position. The limit values recommended by the DIN standard again serve as a guideline:

Especially in the edge areas to the wall or wherever the tiles are adjacent to other rigid components, a width of 5 mm should not be undercut under any circumstances. To be on the safe side, in this case it is even better to increase to 8 mm. Professional planning and exact calculation of the joint dimensions is definitely advisable.

Excursus: Attention with narrow joints!

However, since the joint pattern in a room also has visual effects, care should be taken to ensure a balanced distribution and the most uniform width possible of all necessary joints. In particular, the continuing trend towards large-format tiles with very narrow construction joints – i.e. the distance at which the tiles are placed on the floor during installation – can sometimes become a problem.

On the one hand, because the considerably wider expansion joints can quickly look unsightly in comparison and thus disturb the overall harmonious impression. On the other hand, the narrower the joints are, the more difficult it is to grout – and improper execution impairs the quality of the joints.

If too much water is added to the jointing mortar to make it more fluid, this can lead to differences in colour and spots in the joints due to different drying phases. While too little water, on the other hand, makes the joint sealant brittle. For this reason, filling with conventional, cementitious jointing compound is only possible from a width of at least 2 mm. Among these, only highly viscous materials with a synthetic resin content can be used, as these are more elastic and can be worked into the joint more easily.

And even otherwise, very narrow joints entail an increased risk of damage. This is because if the proportion of joints is small, moisture can only escape from the floor very slowly on the one hand and on the other hand, tensions are less well balanced.

How is an expansion joint correctly filled?

In order to be able to compensate for the movements of the tiles, expansion joints may only be sealed with permanently elastic sealants. The best known and most frequently used material for this is silicone. The best possible result is achieved if the joint sealing compound is applied as deep as the joint is wide – otherwise, too deep filling can have a negative effect on the elasticity. Tip: You can work particularly precisely if the tip of the cartridge is simply cut to the appropriate joint width.

Since the silicone must not adhere to the substrate under any circumstances, expansion profiles made of foam or plastic are also recommended. These are pressed into the joint before filling and fixed at the edges with adhesive tape. Alternatively, paper strips can also be used.

Practical side effect: In this way, the material requirement is also minimized.

Before filling, dust, dirt or adhesive residues must be thoroughly removed from the joint. This is especially true when existing expansion joints are renewed: They must be carefully scraped out before the new filling material is applied.

After the joint has been sealed, the joint sealing compound is evenly removed with a smoothing trowel. Finally, the attached adhesive tape is peeled off and the excess joint sealing compound and any adhesive residues are removed with a damp sponge.