The 7 Biggest Mistakes When Laying Terrazzo and How to Avoid Them

You've chosen terrazzo. A beautiful choice. A floor that lasts for decades, looks timeless, and holds its value. But then something goes wrong during or after installation. An uneven surface, an unsightly grout line, or stains that can no longer be removed. In the end, you're left with a high-quality floor that didn't turn out the way you imagined. It doesn't have to be this way.

I'm Geert Olsthoorn from De Tegel BV, and I see these situations regularly. Not because people are careless, but because terrazzo is a material with its own character that requires specialist knowledge. We have been working with terrazzo floors for private clients and businesses for many years and know the typical mistakes very well.

In this article, you'll learn which mistakes are most commonly made when laying terrazzo, why they happen, and above all, how to avoid them. This way you can approach your project well prepared — or know exactly what questions to ask a professional installer.

1. The substrate is not properly prepared

This is by far the most common cause of problems later on. Terrazzo is heavy and sensitive to movement. If the substrate is not level, dry, and stable enough, the floor will shift. This shows up later as cracks, loose tiles, or uneven grout lines.

A concrete floor that hasn't fully cured, a wooden floor with too much flex, or a loose sand layer beneath the tile bed — all of these are risks that can lead to damage later.

Solution: Measure the flatness of the substrate before you begin. The requirements for terrazzo are stricter than for ordinary tiles. The substrate must be completely dry. For cement-based substrates, the moisture content should be no more than 4 percent. If there is movement in the floor, this must be corrected before a single terrazzo tile is laid.

2. Insufficient allowance for expansion joints

Terrazzo expands in heat and contracts in cold. This is not a material defect — it's simple physics. If no expansion joints, or too few, are planned, the floor has no room to move. Tension builds up and eventually cracks appear in the material.

This issue is especially relevant in floors with underfloor heating, in rooms with significant temperature fluctuations, or across large, uninterrupted floor surfaces.

Solution: Plan expansion joints at the start of the project, not at the end. As a general rule: one expansion joint every 5 to 8 metres, and always wherever the substrate itself has a joint. The joint must also continue through the tile pattern. A joint that ends in the middle of a tile does not fulfil its purpose.

3. Using the wrong adhesive or grout

Terrazzo is a special material with considerable weight and its own properties. Not every tile adhesive is suitable. If a mortar that is too rigid is used, the floor will be less able to absorb movement. If an adhesive that is too flexible is used on the wrong substrate, too much movement can occur and the joints will be put under stress.

The same applies to grout. The colour, grain size, and composition must suit the terrazzo — both technically and visually. A grout that sets too hard can act like a pressure point and damage the tile over time.

Solution: Follow the terrazzo tile manufacturer's recommendations. Those guidelines exist for good reason. If you are unsure, consult a specialist or your supplier before you begin. The few extra euros for the right product are nothing compared to the cost of repairs later.

4. Grinding and polishing at the wrong time

Cast-in-place terrazzo must be ground and polished after it has fully cured. If grinding begins too early, you are working on a surface that is not yet stable. The result may look good during the work but can later become dull, wear unevenly, or remain prone to staining.

Even with terrazzo tiles that are delivered pre-ground, subsequent grinding may be necessary — for example, to even out height differences between tiles. If the wrong disc or too few grinding stages are used, the surface can be damaged without achieving the desired result.

Solution: Work with patience. For cast terrazzo, wait at least 14 days before grinding. Use the correct grit sequence in the right order, from coarse to fine. Always finish with an impregnated or polished surface appropriate for the intended use of the room.

5. No sealing, or incorrect treatment after installation

Terrazzo — particularly the traditional cement-based variety — is porous. Without a good sealant, liquids penetrate the material. Coffee, oil, or wine can leave stains that cannot be removed. This is perhaps one of the most underestimated steps in the entire installation process.

Using the wrong cleaning products after installation is also a common mistake. Acidic cleaners attack the cement- or lime-based matrix. The surface becomes dull, rough, and wears down more quickly.

Solution: Seal the floor immediately after installation, or after grinding in the case of cast terrazzo, using a product specifically suitable for limestone- or cement-based floors. Then provide the client or customer with clear maintenance instructions: which cleaners may be used, which may not, and when re-treatment is advisable.

6. Not allowing tiles to acclimatise before installation day

Terrazzo tiles are produced and stored — sometimes in a different location and under different climatic conditions. If they are brought directly from cold outdoor storage into a warm interior and laid immediately, they may only adjust after installation. This can lead to dimensional and colour variations that cannot be corrected later.

Solution: Allow the tiles to acclimatise for at least 24 hours in the room where they are to be laid. Open the pallets, restack the tiles appropriately, and give the material time. This costs nothing and prevents problems that can later result in high repair costs.

7. The pattern was not measured out or mapped in advance

Terrazzo makes its impression through pattern, colour, and layout. A floor that was not divided out from the centre, or from a logically chosen focal point, will quickly end up with a narrow strip along one side of the room. This is immediately noticeable.

Even with geometric patterns or terrazzo strips used as expansion joints, the layout should be on paper before the first tile is set.

Solution: Take time during the planning phase. Draw the pattern on paper or use a digital floor plan. Dry-lay the tiles and view the room from all angles before any adhesive is applied. Half an hour of extra preparation can save an entire day of rework.

Conclusion

One thing should be clear: terrazzo is not a difficult material, but it is a demanding one. If you follow the right steps, use the appropriate products, and work at the right time, you will end up with a floor that can last for generations. The mistakes in this article are not meant to put you off — they are meant to prepare you.

You now know where things most often go wrong: with the substrate, the joints, the product selection, the grinding, the sealing, the acclimatisation, and the planning of the pattern. These are seven points you can check thoroughly before installation day.

Are you planning to carry out the installation yourself, or would you like to know whether a particular situation in your home or commercial property is being assessed correctly? At De Tegel BV, we are happy to look at it together with you. No obligation and no sales pressure. Get in touch or visit our showroom.

About the Author

Geert Olsthoorn is Managing Director and owner of De Tegel BV, a specialist in high-quality tiles and terrazzo floors. Geert works with terrazzo every day across a wide variety of projects — from premium private homes to commercial spaces — and shares his expertise on the De Tegel BV blog so that clients and professionals can start better prepared. Not theory from the outside, but insights straight from practice.

Frequently Asked Questions about Common Mistakes When Laying Terrazzo

1. What is the most common mistake when laying terrazzo?

The substrate. Almost all the problems we see later — cracks, delamination, or height differences — can be traced back to a substrate that was not level, dry, or stable enough. This is also one of the problems that is almost impossible to fix after the fact without relaying the entire floor.

2. How do I know if my substrate is suitable for terrazzo?

Use a moisture meter to check the moisture content, and check the flatness with a straight 2-metre rule. If the deviation is more than 3 mm, levelling should be carried out first. If you are unsure, have a professional assess it before you begin.

3. Do terrazzo tiles always need to be sealed?

For cement-based terrazzo: yes, always. This material is naturally porous and stains are almost unavoidable without sealing. For resin- or epoxy-based terrazzo, sealing is less critical, but a protective finish is still recommended. Ask your supplier which product is right for your specific tile.

4. How long before cast terrazzo can be ground?

At least 28 days. During this time the concrete cures fully. Grinding earlier may seem to save time, but the surface is not yet stable enough. This can lead to an uneven result. Patience here is not a luxury — it is a technical necessity.

5. Can I lay terrazzo over an existing floor?

Sometimes yes, but it depends on the load-bearing capacity of the structure below, the build-up height, and the condition of the existing floor. Terrazzo is heavier than most other tile types. An on-site assessment is necessary before making this decision. Do not rely on guesswork.