Floor slabs

Floor slabs are an excellent alternative to floor covering due to their attractive-decorative appearance, durability, ease of installation and relative low cost. As well as the wide variety of patterns, combinations and mounting designs that can be used.

There are different types of rigid floor covering slabs according to their nature, size, shape, surface texture, gloss, colors, use and design.

Slab Classification

Rigid floor slabs can be classified according to:


1.- Sand-cement slabs with the colored and polished stuccoed surface (mosaics). 2.- Polished granite slabs (tiles). 3.- Baked ceramic tiles without glazing (saltillo). 4.- Glazed baked red ceramic slabs (ceramics). 5.- Glazed white ceramic slabs (porcelains). 6.- Reinforced baked ceramic slabs (pavers). 7.- Cut natural slabs (natural granite, coral, marble, etc.).


1.- Very small slabs (25 x 25 and 50 x 50 mm). 2.- Small slabs (100 x 100 and 200 x 200 mm). 3.- Medium slabs (300 x 300 and 350 x 350). 4.- Large slabs (400 x 400 and 500 x 500). 5.- Extra-large slabs over 500 x 500.


1.- Squares. 2.- Rectangular. 3.- Polygonal. 4.- Specials (like puzzle pieces).

Surface texture

1.- Smooth and flat. 2.- Smooth and wavy. 3.- Slightly rough. 4.- Rough. 5.- Rustic (imitating natural stone).


1.- Very bright. 2.- Brilliant. 3.- Semi-shiny. 4.- Mattes.


1.- Full color. 2.- Marbled. 3.- Of various colors. 4.- Imitating materials (wood, marble, etc.). 5.- As pieces of a design with several slabs. 6.- With slab design. 7.- Many others.


1.- For domestic interiors. 2.- For domestic exteriors. 3.- For intense human trafficking. 4.- For automobile traffic.

Installation Patterns

For the installation of slabs on the floors, many different patterns can be followed according to the designer’s taste and combining different types of slabs, both in colors and size and way of laying, some of these patterns can be seen below.

  • Placement patterns
  • Slab combinations
  • Designs

Substrate preparation

Rigid slabs do not withstand appreciable deformations without breaking, for this reason the substrate where they are going to be placed must be a rigid and flat surface that must be carefully conditioned before beginning the installation. A.- Preparation of a soil substrate. Slabs on the substrate ground

On earth substrates it is only recommended to place high resistance slabs, such as cement mosaics (about 25 mm or more thick), thick coral slabs, thick cut slabs of natural granite, granite tiles and the like .

These slabs are often supported by a mixture of sand and cement with a composition of 5 to 8 parts of sand for one part of cement, in the soil of the substrate that has previously been leveled and compacted strongly. The mix should have a thickness of at least 20 mm, and will be placed under the slabs during assembly and leveling.

Concrete base

This is the safest and most used way to install rigid slabs, which will serve as a decorative covering to the concrete floor.

It should be borne in mind that the concrete floor must meet the construction regulations of your locality, and in no case should it be less than 50 mm thick, preferably reinforced by a maya or steel rods to avoid future cracks.

Large flat areas of concrete should have so-called expansion joints. During the assembly of the slabs, it must always be achieved that one of the joints between the slabs remains on this joint and never the slab itself, otherwise, with time, the relative movement of the pieces of the concrete substrate will end forming a crack in the surface of the slabs of unacceptable appearance. Although this crack will always form, if it remains in the filling material between slabs, it is practically not distinguishable. If this is not possible, there are fiberglass cloths on the market, which are placed on the expansion joint to avoid, in most cases, undesirable cracking of the slabs.

The concrete substrate must be perfectly level and flat to achieve the subsequent assembly of the slabs, with the least amount of mortar-glue, which is notably more expensive than concrete. B.- Preparation of a wooden floor substrate. When laying slabs on wooden floors, it must be reinforced to increase its rigidity and also covered with a material that guarantees the proper adherence of the slabs to the substrate. In practice two types of reinforcements are used or the combination of both; thick plywood sheets and thin pressed fiberglass reinforced mortar boards.

  • Reinforcement with plywood sheets (plywood)

As already noted, rigid slabs do not withstand appreciable deformation without breaking, for this reason low-stiffness wooden floors are covered with a layer of plywood. These boards are used from 16mm thick onwards and are bolted to the wood substrate using checkered screws at a distance of 150mm. Some use corrugated shank and large flat head nails for this purpose.

Once the floor is covered, and to improve the adhesion of the slabs, a fine steel maya is strongly stapled on the upper surface that will serve as a framework for the mortar-glue. The most demanding ones cover the plywood layer with another layer of fiber-reinforced mortar, screwing it with the same pattern mentioned.

  • Reinforcement with cement and fiber boards

One way to reinforce flexible wood floors is to cover them with a layer of fiberglass reinforced pressed mortar boards or any other type of cementitious board, using a screw pattern the same as in the previous point. These plates must be 12mm or more thick.

In other cases, the plank is fabricated “in situ” using a fine steel maya stapled firmly to the wood substrate, which is then coated with a continuous layer of at least 20mm of good cement-sand mortar.

C.- Preparation of the substrate in high floors

It is common for buildings with two floors or more to have noise emission standards that do not allow the tiles to be placed directly on the concrete of the floor without using a noise damping element, which prevents the steps or objects falling on the upper floor the stillness on the lower floor is heard and disturbed.

Pressed cork sheets and acoustic cementitious mixes are used as noise attenuating elements.

Use of cork sheets

The cork in plates used as noise attenuators in the substrate of the slabs, are specially made for that purpose. They are plates of about 6 mm thick, strongly pressed and with a fine and compact grain to support the loads to which the floors are subjected without deteriorating. They adhere to the concrete substrate using a suitable glue. The glue is generally of the contact type.

Use of acoustic mixes

These mixtures are special for this purpose and are made up of very fine sand and cement, to which some light and elastic fiber is added, or a foaming element that gives foamy texture to the mixture during mixing, a texture that remains after setting. . In all cases, the manufacturer’s instructions should be carefully followed when preparing the noise attenuating layer. The most common is that this layer is about 20-25 mm thick.

Preparation of the substrate with existing rigid slabs

This is a controversial topic, and in it there are different trends and opinions, a part of the installers think that with a good mortar-glue, or using a toning glue layer, the new slabs can be placed directly on top of the existing ones without fear of failure. future as long as the current slabs are firmly attached in place. The author of this article has, in fact, installed slabs on slabs for many years, never having received a claim. However, it is fair to say that other highly experienced installers remove the old slabs next to the mortar-glue before reinstalling. It is important to note that the job of removing the installed slabs is by far difficult and laborious, only efficiently performed using electric chisels. AND. – Preparation of the substrate with existing vinyl slabs In this case the same happens in the previous one, the opinions are found, for the author, if the vinyl substrate is rigid and well adhered, the new slabs can be placed on top if fear. In case of poor adherence of the vinyl slabs or that they are installed on a flexible substrate such as wood, they must be removed or reinforced as appropriate, before laying the rigid slabs.

Tools needed

Slab installation is greatly simplified if you have the appropriate tools, these tools can be classified as follows:

1.- Leveling (straight bubble level).

2.- Tracing (thread marker with colored powder).

3.- Mixing (low speed drill with mixing propeller).

4.- Distribution of the mortar-glue (steel toothed trowel).

5.- Cutting (straight cutter, disc cutter and drilling bits).

6.- Installation (rubber hammer and spacers). Materials Needed Three types of materials are required for the installation of floor slabs.

1.- The adhesive: known as; glue-cement, thin-set mortar or “thin set”. It has already been mentioned that thick slabs can be installed directly to a compacted earth substrate, using a common mix of sand and cement. For the rest of the substrates, special mixtures with greater adhesion power are used. These products, generally pre-mixed, are purchased in the market in bags, dry, to which you only have to add water to give it the proper consistency before use. They are, in essence, a mixture of Portland cement and very fine sand as a basic component, to which very fine mineral powders are added to give it a sticky consistency, some polymer that improves adhesion capacity and a setting retarder to lengthen the useful time. before starting to harden.

There are two types, the one made with gray cement (cheaper) and the one made with white cement (more expensive), which does not influence the resistance and final adherence of the product. White is used in case the dark gray color compromises the quality of the work.

2.- The filling material between the slabs: known as; melted, grout or “grout” When installing slabs, it is common to leave a relatively narrow space between them, which is then filled with a colored pasty material that hardens and completes the fixing of the slabs.

This material, like the adhesive, is essentially a mixture of cement and sand to which a powder colorant is added to achieve the desired color tone according to the design of the finished floor. For the most expensive fillers, polymers are also added that have a sealing effect to improve the appearance and decrease the retention of dirt, which over time change the color of the filler lines between the slabs.

3.- The sealant for the filling of slabs: In some cases, after finishing the floor, the filling lines are waterproofed and smoothed with the use of special resins that serve to decrease dirt retention.


After preparing the substrate, deciding on the type of slab and the design to be used, the installation of the slabs begins. This work has four stages:

1.- Tracing of the guide lines. 2.- Laying of the slabs. 3.- Filling of the unions and cleaning. Tracing the guide lines As guides for the installation of the slabs, one or more guide lines can be drawn in correspondence with the work to be done with a thread marker, the following table establishes some elements.


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