This can go either way. We do not recommend filling in your expansion joints. The expansion joints are there for a reason: to force cracks to occur inside them versus in the middle of the floor. If the expansion joints are filled with something solid, it will put pressure outside of them and can cause the floor to crack in other places.
We can fill the joints with a solid product but there are other risks associated with that. Some products won’t last as long as the coating we use. If that product breaks loose, it can cause the coating to delaminate along those areas. So what are your options?
The most common approach is to coat in and out of the expansion joints, not filling any cracks in the joints. This option gives you the longest lasting floor. It allows the floor to shift without causing damage to the coating. The downside is you will most likely see the cracks in the expansion joints especially as the floor shifts. Another option is we can use a flexible product that bonds to our coating to caulk the existing cracks, then coat in and out of the joints.
This looks clean, hides the cracks, and can last the life of the floor. The caulk is very flexible and can absorb most floor movements. If the floor shifts enough you may see the cracks reappear. The last option is to use a joint filler to completely fill the expansion joints with a product designed for it. This turns a 1 day project into a 2 day project. We would need to come out a day or two prior to the install to prep and fill the joints. For the product to adhere properly, the joints need to be ground. Once this step is complete, we fill the joints with an epoxy based compound.
This compound is self leveling and creates a seamless looking garage floor. If your concrete shifts over time, you may begin to see cracks forming over the seams.
There is no warranty for issues that arise from filling expansion joints with a caulk or joint filler.