In this column dedicated to porcelain stoneware we have talked in recent months about how valuable this material is and how it can have surprising aesthetic results. Today we enter a little more into the technician, facing the questions that are asked most often in our work on this material: if you are looking for the answer to some doubt, we are sure that in these 10 points you will surely find the solution!
1. Porcelain stoneware is the ideal solution for underfloor heating.
Porcelain stoneware, having a high thermal transmittance, is one of the best materials you can choose in case of underfloor heating: compared to other materials, in fact, it retains very little heat, allowing you to optimize the consumption of heating. So porcelain stoneware is not only suitable for underfloor heating, it is also advisable!
2. Porcelain stoneware can be used both on the floor and as a wall covering.
Tiles made of this material are suitable not only for the floor, as they are able to withstand heavy foot traffic, but also for wall cladding, as they are stronger than normal single-fired or double-fired tiles. If the tile you like is porcelain stoneware, you are free to decide where to use it without any constraints!
3. Porcelain stoneware can be used both indoors and outdoors: it does not suffer the elements!
Porcelain stoneware does not absorb – at least – 99.5%, the minimum limit imposed by law. In reality, almost all quality Italian ceramics reach a non-absorbency of 99.8-99.9%. Since it does not absorb, the tile cannot suffer from frost or any other type of weather. The only difference between indoor and outdoor tiles is the slip resistance: if you are tiling a balcony or sidewalk, you obviously don’t want to slip the day it should rain!
4. Proper cleaning of porcelain stoneware is done with a few chemical agents.
Unfortunately, this is our bad habit that we have been carrying on for a few decades: the floor, as well as all the bathroom furnishings, we clean them with supermarket products highly advertised but … tremendously inadequate.
The porcelain stoneware floor, as we said, absorbs practically nothing: using detergents for cleaning with a high amount of chemical residues is therefore not only useless, but even risks creating a surface patina that will seem particularly unsightly. If this happens, it is not a serious matter, just do an extraordinary cleaning with special products to restore the original floor. But to avoid this inconvenience you can choose from the first day products that contain less than 1% surfactants: you can find this information on the packaging of detergents (and the web may be more helpful than the supermarket).
5. Porcelain stoneware is drilled with a diamond tip.
Stoneware is so hard… that you need a drill bit to drill it. This drill bit is called a “diamond drill” and it is often specified that it is suitable for drilling porcelain stoneware. Whatever good drill your plumber has, if it’s not the diamond drill, it’s not suitable for drilling stoneware. The risk? To ruin the tip but above all to damage the tile. With the right tip, however, there is no kind of risk. The cost of a tip is about 20 €, a very sustainable expense for a professional in the field.
6. Porcelain stoneware does not change colour over time.
The tiles are fired at temperatures above 1200°C and the dyes used all derive from natural elements: this is also a guarantee for the stability of the colour, which will never change over time, even under UV rays.
7. Not all glues are suitable for laying porcelain stoneware.
When we happen to go on a tour of a large-scale retail store we usually see people buying porcelain stoneware tiles and then the cheapest bag of glue on the shelves: they could do nothing worse! All the glue on the back of the bag have a certificate that guarantees the performance of that adhesive: if they are inadequate, the tile will not be properly glued to the bottom of the laying, with risks that can be serious. The minimum certification for cementitious glues that can be used for porcelain stoneware is C2: if you find C1 written on the bag, therefore, you can discard that glue. If the tile has a medium-large format, instead, go without delay on a glue with C2TES1 certification: you will spend a few more euros, but it is undoubtedly money well spent!
8. Let the tiles be laid with a levelling system.
Tiles with a side length of at least 60 cm, especially if they are ground, must be laid with a levelling system. These systems consist of plastic products – wedge-shaped or knob-shaped – that help the installer to glue the tiles very precisely, avoiding leaving differences in level (“teeth”) between one tile and another. If the installer says that he has been doing this job for 40 years and is good at laying even without these tools… personally we would immediately look for another tiler, because the one you are talking to is certainly not a professional. All the problems that we have seen over the years at the home of customers have always been born with this premise: you decide if you want to take the risk at home.
9. Porcelain stoneware is NEVER laid without escaping.
The minimum joint for porcelain stoneware tiles is 2 mm. Never go below this thickness, you might find yourself with cracked tiles in the future due to settlement movements. Nowadays, there are a wide variety of coloured grouts for filling joints, so that they match the tile: in this way, the joint tends to disappear and the floor will not only be beautiful but also long-lasting.
10. You have to wait at least a month before tiling and that month is really very important.
This is another one of those weaknesses that we often hear (before the problems). If the screed is made in the classic way, i.e. with sand and cement (so excluding, for example, pre-mixed screeds or gypsum-based), it is very important that it is dry before tiling. In optimal conditions (good season, not so humid period, etc.) the screed made of sand and cement dries in 7-10 days for every centimetre of thickness. Considering that the minimum thickness of a traditional screed is 5 cm, it means that you can tile after at least 35-50 days from the day in which the installers have made the screed. Don’t you want to wait so long? Use a pre-mixed screed, its technical data sheet specifies the minimum time to wait (usually 2-3 days). Don’t you want to spend more on a pre-mixed screed? Then wait. Tiling sooner can pose serious risks for the new floor: many tiles may crack after a few days as the screed would not be stable yet.
How many of these 10 points did you already know? For the curious, to investigate any of these topics, there is the UNI 11493 standard. For the others we hope instead that this small vademecum has been a great help.