Which notched trowel size should you use for your tile size?
Bigger tiles require bigger notches, that's the rule of thumb you'll find almost everywhere. And while it's generally true, it doesn't tell the whole story. Choosing the right notched trowel depends on more than just the tile size. Whether you're installing wall or floor tiles, the flatness of the substrate and the profile of the tile back are just as important.
If you base your choice on tile size alone, you risk leaving voids beneath the tile. These unsupported areas can eventually cause tiles to loosen, crack or break.
In this guide, you'll find practical recommendations for different tile sizes and learn why wall and floor installations often require different notch sizes.
General guide by tile size
| Tile size | Wall tiles (Notch size in mm) | Floor tiles (Notch size in mm) |
| Mosaic (<10 × 10 cm) | 3 × 3 of 4 × 4 mm | 4 × 4 mm |
| 10 × 10 to 20 × 20 cm | 6 × 6 mm | 6 × 6 or 8 × 8 mm |
| 15 × 30 cm to 20 × 40 cm | 6 × 6 mm | 6 × 6 or 8 × 8 mm |
| 30 × 30 cm | 8 × 8 mm | 8 × 8 mm |
| 30 × 45 cm | 8 × 8 mm | 8 × 8 mm or 10 × 10 mm |
| 30 × 60 cm | 8 × 8 or 10 × 10 mm | 10 × 10 mm |
| 60 × 60 cm | 10 × 10 or 12 × 12 mm | 12 × 12 mm |
| Large-format tiles (>60 cm) | 12 × 12 mm or larger | 12 × 12 or 15 × 15 mm |
Please note: This table provides general recommendations. The ideal notch size also depends on the substrate, the tile backing and the required adhesive coverage.
Browse our full range of notched adhesive trowels to find the right notch size for your project.
Why do wall and floor tiles require different notch sizes?
Although tile size is the main guideline, the type of installation also plays an important role.
Wall tiles
Wall tiles are generally lighter and subjected to very little mechanical stress. As a result, a smaller notch size is usually sufficient. For small wall tiles, a 4 mm notch is often enough, while 6 mm is commonly used for tiles measuring 15 × 15 cm or 20 × 20 cm. For larger wall tiles, such as 30 × 60 cm, an 8 mm notched trowel is often the best choice. Using a smaller notch also reduces the amount of adhesive applied, helping prevent tiles from sliding during installation while avoiding unnecessary adhesive consumption.
Floor tiles
Floor tiles must withstand constant mechanical loads. Therefore, they require higher adhesive coverage and generally a larger notch size, ranging from 6 mm to 15 mm, depending on the tile dimensions.
As a general guideline:
- Indoor floors: at least 80% adhesive coverage
- Outdoor installations, wet areas and large-format tiles: 95–100% adhesive coverage
A larger notch ensures enough adhesive is applied beneath the tile, reducing the risk of voids.
The substrate matters too
Choosing a larger notch is not a solution for an uneven substrate levelling the floor is. If the substrate is uneven, level it before applying tile adhesive. If you're installing large-format or outdoor tiles and want a perfectly flat finish without lippage, using a tile levelling system is highly recommended.
For example:
- Levelit Starter Kit 1.5 mm for tiles 6–12 mm thick
- Levelit XL 2 mm Clips for larger installations
- Helix Tile Levelling System
- Levelit XL Starter Kit for thicker floor and patio tiles (15–30 mm)
Minor surface irregularities can often be compensated for by selecting a slightly larger notch size, ensuring sufficient adhesive to fully support the tile.
Don't overlook the tile backing
Not every tile has the same back profile. Some tiles have an almost perfectly flat back, while others feature deep ribs or textured patterns. The more pronounced the profile, the more adhesive is needed to fill these recesses completely. In these situations, using a larger notch size helps eliminate voids and ensures maximum adhesion.
Proper adhesive application is just as important
Even with the correct notched trowel, long-lasting adhesion depends on applying the adhesive correctly.
Hold the notched trowel at an angle of approximately 45° and comb the adhesive into straight, parallel ridges. Uniform ridges collapse evenly when the tile is pressed into place, ensuring optimal adhesive coverage. Place the tile into the adhesive and press or slide it slightly to flatten the ridges completely. Always comb the adhesive in one direction. This allows trapped air to escape more easily and significantly reduces the risk of voids beneath the tile.
Key takeaways
- Choose your notch size based on tile size, substrate condition, tile backing and application.
- Small wall tiles generally require a 4–6 mm notch.
- Standard floor tiles are usually installed with an 8–10 mm notched trowel.
- Large-format tiles often require 10–15 mm notches, frequently combined with the buttering-floating method(double adhesive application).
- Always lift and inspect the first tile to verify sufficient adhesive coverage.
Unsure which notched trowel is right for your project? Explore the full range of Nivello notched adhesive trowels and tile levelling systems to achieve a professional tiling result.
