If you have an in-ground concrete pool that is made out of brick or another type of natural stone, you will use an expansion joint that is referred to a mastic. The purpose of this expansion joint is to let the pool along with the pool deck expand when the weather gets warmer. This joint will let the pool wall and the pool deck expand in the heat without coming in contact with each other.
A deck may expand to as much as one-quarter of an inch, and the expansion joints need to be filled up with caulk. It’s a good idea to caulk the joint every five years. If this isn’t caulked, it is going to be filled with sand along with other debris and may eventually cause a lot of damage to the materials. The most important part of caulking is to help prevent leaking and water damage, so don’t leave this step out.