Crystalline waterproofing material is a substance which binds to concrete walls, the penetrates the concretes and hardens to the point where it becomes an impenetrable water barrier. This material protects your walls from leaks, and can be added on new or old concrete. The downside is that installation is a hassle, because crystalline material must stay wet while you are applying it, and it heats up when mixed with water. This material is also relatively expensive as compared to simpler waterproofing options.