Typically grout begins to crack where the floor meets the walls causing water to penetrate below the tile surface. Once this happens, things get bad quickly causing moisture issues resulting in fungus/mildew that can be very hard to keep clean. Neglected floors can lead to costly shower replacement.
So what can we do to eliminate this very common but frustrating issue? We need to understand that grout is not flexible, nor waterproof. Maybe water resistant at best, but that is not good enough for a shower floor. A shower that is used on a daily basis is exposed to not only water, but also harsh chemicals such as soap and shampoo residue. Hard water is even worse that can permanently etch and damage tile/grout.
We also need to understand that any cracks where the shower floor meet the walls should be repaired asap to prevent excess water from getting below the tile. Using caulk or silicone is generally a short lived repair because those products cannot perform up to these harsh environments. They also are prone to allow fungus to develop inside itself which cannot be repaired, only replaced. We need a product that can hold up to wet areas, withstand soap and shampoo residue and not allow fungus to grow inside or under it.
You can restore your shower to better than new condition with some hard work, including elbow grease and proper techniques. It is a good idea to plan on taking up most of the day to properly repair your shower floor, but if you do it right, could be the last time. Using Super Grout Additive™ grout is one of the key components in producing a waterproof grout that never needs sealing and will not crack in corners.