Why Tile Caulk Cracks
- Many tile jobs use a latex-based caulk in the expansion joints between tubs and tile walls, or between two corners of tile. Latex is easy to use and easy to clean up, but it doesn't have as much flexibility as other materials. Other caulks may be able to flex quite a bit, but it may not be enough for some homes. If your house settles a lot, or there is a lot of flex in your substrate, which can cause walls and floors to shift, this can cause caulk to crack. Depending on the type of caulk and the amount of flexing, the cracks may be very small, or the caulk may crack completely.
- Most caulks are meant to move in two directions. They can pull for expansion and they can also contract. Most, however, contract far less than they're able to expand. If settling causes a wall to come severely out of plumb, this can cause the bottom rows of tile to contract, either into the base of the tub, or into one another in the corner of an installation. Once the caulk has met its maximum amount of contraction, it will crack beneath the weight of the tile.
- Caulk shrinks very slightly as it's curing or drying. This is natural, as the water or liquid in the caulk begins to leave, giving it a tight seal with the materials it surrounds. If not enough caulk has been placed inside a joint, this shrinkage will cause the caulk to pull inward into the gap. Sometimes this shrinkage is severe enough to cause an immediate "valley," which must be filled with more caulk. Other times the shrinkage is not readily apparent, but causes the caulk to lose its grip on the materials it surrounds. Over time, as the caulk dries out, it shrinks even more and causes cracks.
- Caulk has a lifespan. Some caulks, like pure silicone, have a 50-year lifespan, while others will only last for five or 10 years.
Over time, the caulk slowly loses moisture and begins to dry out. This causes the caulk to become brittle rather than flexible as it was when it was first applied. When this occurs, the caulk becomes prone to cracking under even mild expansion or contraction. If the caulk has shrunk significantly as it has dried, this can also cause cracks to form as the caulk reaches the end of its useful life.
