Wet areas/bathrooms

For a long-lasting installation, before cladding, the surface must be fixed, smooth, dry, clean, and load-bearing. Substrate preparation depends on its type (vertical or horizontal cladding).

1. Flooring

For a concrete substrate (the most common), preparation involves:

cleaning the surface (removing construction debris and stains)
applying primer to even out water absorption and increase adhesion
pouring a leveling screed, possibly followed by a self-leveling screed
applying waterproofing.

Waterproofing is applied both to the floor and, partially, to the walls (about 20 cm up). Special corner pieces are used at corners, and a membrane strip is applied along the wall-to-floor joint. For a wood substrate, the first step is securing the flooring, followed by applying primer.

Cladding over a surface already tiled with ceramic tile, after removing the old tiles:

Removing old tiles: a rotary hammer drill fitted with a chisel bit is used. The chisel tip is inserted into the gap between tiles; the vibration and pressure created break the tiles apart.
Removing old mortar residue stuck to the floor: the same tools are used; the chisel tip is placed at the edge of a piece of mortar and pressed. Vibration and pressure help remove the residue.
Underfloor heating, if present, is switched off.
Cleaning the surface: large pieces of ceramic tile are removed with a shovel, and an industrial vacuum is used to remove debris. The surface must be left clean.
Checking whether the remaining substrate has any stains. If it does, their nature must be identified and, if possible, removed.
After cleaning, the surface is rinsed with clean water.
The surface is left to dry, making sure water doesn’t pool (excess water is removed so it doesn’t seep into the floor).
Measuring the surface: a tape measure or folding ruler is used. This step is needed to determine how many whole tiles fit on the surface and how many will need to be cut. It’s a good idea to draw a scaled sketch on paper showing how the layout should actually look; this helps calculate where cut tiles will go, their size, and also checks the number of whole tiles to be installed.
A dry run (cold layout): a row (whole or partial) of tiles is laid out on the surface, and it’s decided how the edge tiles (the ones that don’t fit) should be cut. Tiles are numbered on the back.
Checking the finish and coloring, and deciding on the layout. If a pattern is wanted on the surface, it’s recommended to lay out the tiles according to the pattern, simulating the arrangement before installation. It’s a good idea to check the packs to spot color differences representing different selections of the same stone type. Tiles are then arranged in the desired color layout.
Checking installation conditions are met: dry tiles (protected from moisture for at least 24 hours before installation), installation temperature between 5 and 25°C (both indoors and outdoors), normal humidity.
Preparing the adhesive per the manufacturer’s instructions.
Starting the actual installation, based on the stone’s absorption level. For stone with higher water absorption (limestone, travertine), it’s recommended to dampen the back of the tile with clean water using a sponge before installing it. This keeps the tile from absorbing moisture too quickly and increases its set time. Tiles made of low-absorption material (granite, slate, marble) are installed by direct application.
Spreading the adhesive continuously over the surface using a notched trowel. Depending on the adhesive’s drying time, it should be applied to smaller areas so it doesn’t dry before the tile is installed. Adhesive can be applied to the surface only, or to both the surface and the tile (for large tiles). For cladding in wet areas, at least 95% coverage of the tile back with adhesive is required.

Large tiles often come from the factory with slight unevenness or warping; this can be compensated for with adhesive, using a 10-20 mm notched trowel to create deeper grooves on the tile surface. For small tiles, a smaller notched trowel is used, with at least 60% coverage. The application technique is “combing,” not “dabbing,” since perfect adhesion is essential. Adhesive is applied in a straight direction without curving the trowel. This produces a series of small parallel grooves on which the tile is laid. For rectangular tiles, the adhesive is applied so the grooves run perpendicular to the tile’s width. All these steps aim to increase adhesion. If large tiles or panels made of small stone pieces glued together (15 x 60 cm) are used, it’s recommended to also apply a layer of adhesive to their back for the best possible adhesion.

Cladding starts from a corner to ensure the tiles are aligned. The tile is placed directly on the surface and pressed gently, possibly wiggling it slightly forward and back without rotating it. The surface must be flat. A rubber mallet can be used to seat it.
Installation without joints allows continuous patterns to be laid out across the clad surface. Whole tiles are installed, with the gaps at the edge of the surface left empty. After installation, excess adhesive is removed with a damp sponge. For heated floors, installation is done with joints. The same applies to large, unrectified tiles (not cut at a right angle), or tiles with warping or unevenness. Spacers (small crosses) are used to set the joint width. Indoor cladding typically leaves joints of 1-2 mm.
The clad surface is left to dry for at least 1-2 hours, or as long as stated in the adhesive’s instructions, without walking on it.
After installing the whole tiles, unclad areas will remain, either along the edges or around obstacles. Tiles must be cut to size for these spots. The areas needing tiles are measured, and cut lines are marked on each tile, leaving room for edge spacing.
Preparing the tile-cutting machine: it has a water-cooling system, and cutting is done with a diamond blade. The tank is filled with water, the machine is started, and left running empty for a few minutes until the diamond blade is wetted by the water. The machine is stopped, the tile is placed and secured, and the blade is positioned on the marked line. Preparation steps are carried out as indicated by the manufacturer. Stones vary in hardness, and the machine (diamond blade) must be chosen based on the stone being cut.
The marked tiles are cut, left to dry, and then installed the same way as the others.
The surface is left to dry naturally (about 24 hours), without walking on it. If installed with joints, the spacer crosses are removed.
For installations with joints between tiles, these are grouted with a special grout.
After grouting, excess is removed and the surface is left to dry (24 hours).
The surface is washed with clean water.

(Images: HORIZONTAL CLADDING ON MASONRY AND WOOD SUBSTRATE)

2. Vertical cladding

For a masonry substrate (AAC block, brick), the process involves priming, plastering the walls with base plaster and finishing coat, and applying waterproofing. Drywall walls are primed. Plastering is not needed. In areas that won’t be clad, skim coat or paint can be applied.

In bathrooms, basements, kitchens, roofs, foundations, shower stalls, outdoor terraces, and other wet areas, waterproofing often needs to be applied to ensure sealing before installing stone tiles. Waterproofing is a membrane or coating applied to the surface that prevents water from getting in. Without waterproofing, water can seep in through the joints between stone tiles, with some very unpleasant consequences: flooding, mold and damp, tiles coming loose or breaking, the screed crumbling, water stains, and the characteristic smell of a damp environment. In a bathroom, waterproofing is applied to the floor (fully), to the vertical walls (partially), and in the shower stall (fully, both floor and vertical walls).

Waterproofing is applied according to the manufacturer’s instructions, in the following main steps:

Pouring the screed – done after the pipework is installed.
Cleaning the surface – once the screed has dried, the surface is cleaned, removing residue, dust, and grease.
Preparing the surface – before applying waterproofing, cracks in the surface and gaps at the wall-to-floor joint are sealed (silicone can be used). Some manufacturers also recommend applying a primer coat.
Applying the first waterproofing coat. This is applied using common tools: a wide brush, roller, paintbrush, trowel, and gloves. Waterproofing thickness ranges from 1 to 2.5 mm, depending on the manufacturer and the area being treated.
Applying sealing tape at the wall-to-floor junctions, at the junction between two vertical walls, over expansion joints, and around pipe penetrations.
Applying the second waterproofing coat – applied perpendicular to the first coat, including over the sealing tape, after the time specified in the manufacturer’s instructions.
Washing tools after use – needed to prevent the waterproofing from hardening on them.
Wall and floor cladding is carried out a few hours later, once the waterproofing has dried (per the manufacturer’s instructions).
Waterproofing in shared wet areas uses the same materials, with a third waterproofing coat also applied where water under pressure is involved.

Flexible waterproofing is recommended.

Plastering walls

Plastering is done directly on masonry. It’s needed to provide a suitable substrate for cladding. Plaster protects walls from environmental factors and also plays a decorative role. It’s applied both indoors and outdoors. Base plaster is applied directly to the masonry, followed by a finishing coat used for the final finish. Base plaster with good resistance to mechanical impact and strong adhesion is recommended. Finishing coats are used to even out surfaces, resist environmental factors, and let the wall breathe. After plastering, the wall is ready for stone installation. Plastering follows these main steps:

Preparing the surface – the wall must be dry, solid, and clean.
Applying the scratch coat – a cement-slurry primer spread over the surface using a trowel. Its role is to even out the substrate’s absorption.
Installing guide rails (screed rails) – installed after the scratch coat has set, starting with the outer ones (about 30 cm from the wall edge). A string line is marked between them. Intermediate rails are installed at distances ranging from 0.8 to 1.50 m apart. Their verticality is checked with a spirit level.
Applying the first plaster coat between the rails (2-2.5 cm thick) – applied once the rails have set, using a trowel and float. Finished off with a straightedge. Excess material is reused.
Applying the second coat (wet-on-wet) – the first coat is left to firm up slightly, then the second is applied.
Applying the finishing coat – floated with a large trowel. The plaster is partially dry.

Once walls are plastered with a finishing coat, skim coat can be applied, or you can move straight to stone cladding. Exterior façade plaster can be part of the house’s thermal insulation system.

Pouring the screed, applying waterproofing, and plastering walls are all steps that come before cladding, especially needed indoors. Indoors, specific steps are also carried out before installing countertops, steps, and window sills. Outdoors, excavation is done for installing paving (especially cobblestone or polygonal stone) and for pool installation.