How to lay slabs on pedestals?

Despite the hectic pace of daily life, it is always necessary to spend good times with friends or family on the terrace. If you don’t have one, it’s high time to install one, if the budget is ready, of course.

Before you start, know that this project causes quite a bit of disorder in your outdoor space. Fortunately, there is a solution that facilitates earthworks. It is the installation of tiles on pedestals.

Steps to lay tiles on pedestals

• Prepare the base: make sure the ground is stable, clean, and level (terrace, concrete slab, or compacted soil).
• Determine the placement of the pedestals: place them respecting the size of the tiles (generally at the 4 corners and in the middle for large tiles).
• Adjust the height of the pedestals: adjust to obtain a flat surface and a slight slope for water drainage (about 1 cm/m).
• Lay the first tile: check alignment with a spirit level.
• Continue laying: place the following tiles by slotting them onto the pedestals’ lugs to ensure regular spacing.
• Adjust if necessary: correct the height of the pedestals or the positioning of the tiles to maintain perfect alignment.
• Check the whole: make sure the final surface is flat and stable.

---

Principle and use of tile on pedestal

To better clarify the subject, it is appropriate to define what is meant by pedestal for tile. Simply put, it is an intermediate support with an adjustable height between 35 mm and 230 mm.

Step	Objective	Materials used
Ground preparation	Have a stable base	Broom, level, possible geotextile
Placement of pedestals	Support the slabs	Adjustable PVC pedestals
Height adjustment	Obtain a flat and inclined surface	Bubble level, ruler
Slab installation	Create the terrace	Concrete, stone, ceramic slabs
Final adjustments	Ensure solidity and aesthetics	Adjustment keys, mallet

This high-quality plastic support is installed between the ground and the paving. It not only serves to raise the slab but especially to stabilize it, simplifying the construction of the terrace.

The pedestal generally consists of a base or a footing, an adjustment nut, an adjustable head, fins, and a locknut.

It demonstrates remarkable robustness to withstand countless stresses such as temperature variations and load.

The principle of the slab on pedestal is ultra simple. It does not rest directly on the mortar layer. Instead, the slab rests on pedestals with adjustable height according to your requirements.

Installing a terrace slab on pedestals

Type of support	Adjustment height	Maximum load	Ideal use
Fixed pedestal	8 to 15 mm	1000 kg	Low height, flat ground
Standard adjustable pedestal	25 to 120 mm	1200 kg	Classic terrace
Self-leveling pedestal	40 to 260 mm	1400 kg	Steeply sloped ground
XL self-leveling pedestal	260 to 500 mm	1500 kg	High elevation

According to specialists, four pedestals are needed to support a slab, regardless of its shape, rectangular or square.

Before installation, these plastic supports must be pre-installed on the ground. Thanks to this technique, the covering of your terrace is not only waterproof and solid, but it will also last you many years.

In general, almost all traditional materials can be adapted to this pedestal installation method. However, it remains necessary to respect certain conditions such as selecting high-quality material.

Since the terrace is subjected to harsh conditions, the material must tolerate climatic variations. Although exposed to the elements, it must demonstrate great resistance.

Similarly, a material with consistent thickness is highly preferred. This allows for a surface without irregularities.

Stability problems are very common when working on an uneven surface. Moreover, this condition complicates the placement of the slab on pedestal. Nothing beats a solid and flat ground promising better results.

In any case, it is possible to carry out this installation on an old terrace, a concrete screed, or an indoor floor.

How to install a terrace slab on pedestals?

With the intervention of a professional, this project seems relatively simple. However, it must be carried out with extreme care. For its success, it is preferable to have a slab that is sufficiently hard, such as concrete.

That said, the first step of the installation consists of defining the type of pedestal to install under the terrace slabs. Preferably, self-leveling pedestals with fins are among the specialist’s recommendations.

Plan for a slope between 1.5 to 2 cm per meter. If the surface already has one, you just have to follow it. Otherwise, you must make a screed on the slab. It is also possible to adjust the pedestals to create the slope.

Once this phase is finished, you need to proceed with the layout or diagram to help you define the structuring of the pedestals and slabs to be installed. Use a tape measure, a mason’s ruler, and marking chalk to draw a grid that facilitates their placement.

The next step is to prepare the pedestals. To do this, adjust each element by turning its head to obtain the correct height. Then secure the fin component located at the base of the support.

Now arrange all the pedestals on the ground. Remember to take into account the size of the slab at each location. Remove the fins now and lay the slabs starting from the top row.

Use a screwdriver to adjust the pedestals during the installation of the terrace covering. Use a spirit level to check the alignment and slope.

As for the finishing, do not hesitate to make some adjustments if necessary. A grinder equipped with a diamond blade can be useful for making cuts.

If the results do not satisfy you, you can correct the work by removing the slabs with a special lifting clamp. Likewise, the height of the pedestals can be adjusted according to your needs.   

Advantages and disadvantages of slabs on pedestals

If pedestal slabs are attracting more and more people, it is notably due to their proven robustness. They can support a load of up to one ton.

This type of flooring offers high resistance to seasonal weather conditions. Durable, it can be used long-term without deteriorating, even over many years.

That’s not all, it provides perfect waterproofing despite high humidity. With its finish using recyclable materials, it promises good impermeability. The pedestal terrace does not retain rainwater runoff. It shows no signs of moisture.

Thanks to the ventilated space between the ground and the slab, its installation promotes thermal dispersion of the sun’s rays. Once the flooring is installed, it generally requires no screws, no grouting, no glue, and no nails.

As for their drawbacks, it must be said that pedestal slabs do have limits. They must be installed on stable ground. Otherwise, it affects their durability and quality.

If you equip yourself with slabs or pedestals of poor quality, do not expect miraculous installation results. It remains essential to always have first-class components.

If you want to know how to install pedestal slabs, also discover the key steps to install tile on pedestals, compare possible materials with the interlocking paver guide, and get inspired by tips to build a garden shed.

FAQ – Pedestal Slabs