Speed: let’s talk reaction time. While the single component products can have their set time field adjusted, two-component products will almost always react faster. This is helpful when you have gushing leaks, but often you want to give your grout a longer time to migrate and permeate before they react to ensure you get the whole leak. Remember, 99% waterproofed is 100% leaking.
Both types of grouts are isocyanate-based and are closed celled. They both are highly resistant to chemicals, and neither are UV stable. The two-component grouts are always hydrophobic whereas the single component can be either hydrophobic or hydrophilic. In general, most two-component urethane grouts are rigid or semi-rigid. On the other end of the spectrum, single component polyurethanes can be a gel, a flexible foam, a semi-rigid foam, or even a rigid foam.
So, with all that said, single component foams are the traditional choice for leak seal. When it comes to crack and joint water mitigation, flexibility is key and that rules out most of the two-component foams. When we look at curtain grouting, both can be very effective and there can be a substantial cost saving when it comes to two components. But a downside of using two-component is the shorter set time and thus less travel.
In summation, for leak seal, single component grouts can do everything that is needed and are the typical grout of choice.