What Causes Lippage (Uneven Tile Edges) Between Slabs?

In short: The plate edges that catch your bare foot when you walk or rattle when a vacuum cleaner passes over them are called lippage, or height difference.

It spoils the appearance and also causes the edges to chip. In this article, we explain the causes of lippage and how it is corrected by grinding.

What Is Lippage?

It is when the surfaces of two adjacent tiles are not at the same level. The difference is sometimes less than a millimeter, but when light hits at an angle it casts a shadow and can be felt by hand.

Causes

During Installation

Most lippage begins during installation; it stems either from the tile itself or from the way it was set in place.

• Tiles of different thickness: Even within the same batch, tile thickness can vary slightly; if the installer does not compensate for this with mortar, the thicker tile sits higher than its neighbor.
• Unevenly spread mortar: If adhesive or mortar is not spread evenly under the tile, the tile rises at one corner and sinks at another, creating a step along the edges.
• Level errors: If the installer does not regularly check levels with a string line or spirit level, small differences between tiles accumulate and spread across the entire room.
• Warped or crooked edges: If the tile edges are slightly warped or cut crooked, one edge stays higher along the joint line even when the tile is laid flat.

Over Time

Even a floor laid flat can develop height differences over the years through use and structural movement.

• Settling of mortar voids: A tile with a mortar void underneath gradually sinks as it is stepped on and ends up lower than the neighboring tiles.
• Movement of the substrate: Settlement in the screed or slab, shrinkage, and small structural movements push the tiles in different directions and create height differences at the edges.
• Concentrated heavy loads: Loads such as a cabinet, piano, or heavy furniture bearing on specific points can cause the tiles in that area to sink over time.

Harms of Lippage

Even if the height difference looks small, it negatively affects safety, the durability of the floor, and its appearance.

• Risk of tripping and falling: A raised edge catches the foot, especially when walking barefoot or in slippers; it can cause falls for the elderly and children.
• Chipping at the edges: The higher edge takes every impact and every dragged object on its own; over time a piece breaks off the edge or a crack forms.
• Dirt buildup on the edge: Dust and dirt collect in the step between the low edge and the grout joint; because the mop does not reach it, the joint lines darken.
• Uneven shine: The polishing pad touches the high edges more and the low spots less; the polish looks wavy and shadows become pronounced in raking light.

Correction by Grinding

The permanent solution to lippage is coarse grindingThe process is carried out in three stages.

1. Grinding down the high edges: First, the high edges are ground down with coarse diamond abrasives; not only the edge but also the surrounding area is ground to smooth out the transition.
2. Creating a single plane: Then the whole floor is brought to a single plane; the machine grinds the tiles and joints together, removing steps that can be felt by hand.
3. Intermediate stages and polishing: Next, the intermediate stages and polishing are carried out; the scratches left by the coarse diamonds are removed step by step and the surface reaches the desired shine.

In this process, not only the high edge but also its surroundings are ground together, so the transition is smooth.

Limitations

Coarse grinding eliminates most height differences, but in some cases another intervention is needed first.

• Very large height difference: When differences of more than a few millimeters are removed by grinding, there is serious loss of stone thickness. In this case, re-laying the tile may be the better option.
• Hollow (loose) tile: A tile with a void underneath cannot be corrected by grinding; it must first be secured or replaced, otherwise it may crack under machine pressure.
• Broken edge: If the edge is chipped, it is first repaired with a color-matched filler; only after that can grinding bring the damaged area to the same plane as the floor.

On New Installations

Some height difference is very common on newly laid floors. For this reason, the first grinding after installation is also done to eliminate height differences.

Approach by Degree of Height Difference

Lippage and Joints

On floors with height differences, the joints usually deteriorate as well; along the higher edge the grout cracks, while dirt accumulates on the lower edge. During coarse honing, the joints are ground down together with the slabs and the surface is brought to a single plane. At this stage, emptied or cracked joints are cleaned and refilled. Honing slurry is sometimes used to fill the joints as well; this way the grout color matches the floor.

Preventing Chipped Edges

Lipped edges are the points most prone to chipping; if precautions are taken early, both repair work and stone loss are reduced.

• Correct them before they chip: Lipped edges should be corrected by honing before they chip; once they chip, the job grows into filling and repair, and the mark may not disappear completely.
• Do not drag items: Furniture and heavy items should not be dragged across lipped edges; if they are lifted when moved, the protruding edge is not hit.
• Repair chips with filler: Chipped edges should be repaired with color-matched filler; an open chip collects dirt and also weakens the surrounding stone.
• Secure hollow slabs: Hollow slabs should be secured without delay; a slab with a void beneath it shifts as it is stepped on, and its edges hit its neighbors and chip.

Lippage Correction in Alanya

In newly built homes and renovated apartments in Alanya, we encounter lippage on marble and granite floors very often. On floors with height differences, we first check for hollow slabs, then bring the floor to a single plane with coarse honing and finish with intermediate grit stages and polishing. For slabs with very large height differences, we openly discuss the option of re-laying.