The Key to Urethane Grouting

With Urethane Grouting, it’s all about the Prep Work

urethane grouting mixing process
Photo of the mixing process for a commercial urethane grouting job in an Alabama office building where the goal was to fill voids and lift the floor.

A urethane grouting job is successful IF the preparation of the grout is done right. Everything depends on a thorough inspection of the problem and on the grout mixing process.

There are four major factors in how you prepare the urethane grout after you have inspected the area in which it will be used:

  1. The percentage of accelerator added to the mixture. This will determine how the mixture sets up and when.
  2. The ambient air temperature.
  3. The temperature of the grout mix.
  4. The amount of moisture within the soils or concrete being grouted. Note that it only takes 2% moisture to activate the urethane grout.

The set time which the grout begins expansion can be adjusted (from 30 seconds to 5 minutes) based on the factors above.

Mix time varies based on the material, but we mix for a period of time that allows the molecules to bind together between the accelerator and the rest of the mixture.

You will notice when we are working on a urethane grouting project we may do a test process of adding the mixture to a cup. We will swirl the cup and wait. In this test, we are timing the urethane grout for expansion and set time.

Why do we use Urethane Grout vs. Other Foam Grout?

In your research on grouting for void filling and concrete leveling you may have read or seen video on polyurethane foam. You will notice if you’ve seen videos that polyurethane grout or foam grout starts expanding the moment it leaves the nozzle during the application. The urethane foam that we mix gives us so much more control. Because we control the amount of accelerator, we can adjust when the grout expansion and set time occur. We want the grout to flow down and into voids and then expand. These voids and spaces are at different levels. We also can pump grout through pipe we have driven down into a void.

Simply said, we are in control of the grouting process, the grout doesn’t control how we use it.

In the video below you can see the urethane grouting process at work. In this case, we will performed a commercial job in an office building. The task was to fill voids but also to lift the floor in the building. We mixed for two minutes of high-speed mixing. The mixture in this case was set to expand in 4 minutes, giving us time to allow the material to flow into the voids and spaces prior to set and expansion time.


If you have questions about the urethane grouting process for your sunken floor or void filling needs, call us. Every application is unique but urethane grout allows us to provide custom solutions. We look forward to helping you!