It is really disheartening to find cracks in the grout of your newly completed mosaic project, particularly after you've invested significant time, money and creativity.
Common reasons for grout cracking include:
- Allowing the grout to dry out too quickly which may cause shrinkage. Resist the temptation to place your project in front of the heater to dry it out more quickly. Grout needs time to cure properly and strengthen.
- Adding water to your grout after it has begun to set. Doing this may cause the mixture to weaken, which will cause the grout to crack.
- Not applying the grout properly. When applying your grout it must penetrate the cracks between the tiles, there should be no air pockets between the tiles and the base. Make sure you invest time working the grout into the spaces between your tiles.
- When you mix dry grout with water, microscopic holes are formed as the water evaporates and grout hardens. When mixed in the correct ratios, this isn't a problem. If too much water or not enough water has been added to the grout however, the holes can become too large resulting in the grout cracking and weakening.
- Movement in your substrate. This can be caused by the expansion and contraction of materials such as wood or metal due to temperature changes and / or moisture.
Adding a grout additive to your dry grout will assist in preventing cracking, as it will improve the grouts flexibility.