With ever-growing pressures to complete buildings on tight schedules, flooring and subflooring contractors often feel pinched from multiple sources. Owners, designers and general contractors demand high quality, along with rapid installation. For contractors installing self-leveling underlayment (SLU), this means new approaches are needed to complete work faster and more efficiently. Pumping of SLU can help address these challenges.

Conventional Techniques

Traditionally, concrete underlayment installation has relied heavily on manual processes. Water and cement-aggregate compounds are mixed in large barrels, typically using drills equipped with paddles. The barrels are wheeled to the desired location, and the mixture is poured and distributed manually. After each batch is placed, the process is repeated and another batch is placed adjacent to the previous batch.

For larger jobs, this process makes it difficult to maintain a “wet edge,” a necessity for a homogeneous pour. The manual process is also labor intensive, requiring more people for larger jobs. Significant coordination is needed to clear the work area and time batch placement for proper curing and access.

A Different Approach

With SLU pumping, scheduling challenges can be greatly reduced. Placement can generally be completed faster with fewer people. Since larger rooms do not necessarily require additional workers, these resources can be applied elsewhere on the project or on other projects.

Time savings begin with the material mixing process. Using combined mixing and pumping units, water can be mixed automatically with cement-aggregate compounds in prescribed amounts. SLU mixtures can be pumped up to distances of 300’ and heights of 60’.

Alternatively, separate mixing and pumping units can be employed to generate higher volumes and pump greater distances. Using certain mixers and pumps, up to 300 50 lb. bags of SLU compound can be mixed and pumped per hour, with pumping distances of up to 400’ and heights of 150’.

Coordination of batch placement is another challenge greatly simplified with pumped SLU. Instead of manually placing batches that must be matched, pumped SLU can be placed in a more continuous manner, with multiple passes made in a zig-zag pattern. This enables workers to place SLU in widths of just a few inches at a time or several feet at a time, while maintaining a “wet edge” and more continuity in the SLU layer.

SLU pumping can also simplify setup and equipment transportation. Smaller pumping products can be loaded and transported in a standard pickup truck. Those with built-in wheels can be transported around a job site easily.

Other Benefits

The automated approach improves mix consistency and placement precision. With water flow rates set according to manufacturer’s recommendations, compound materials and water can be mixed within the mixing chamber at the same rate all day long. The units can be used to correct uneven floors, repair damaged concrete and provide a smooth surface for carpet, tile or other floor coverings. While skilled workers are still needed to place SLU, skill sets from other crafts are often transferrable. Crews that can place stucco can generally place SLU, for example.

As another example, assume two crews of six persons each, with one crew pumping SLU and the other placing SLU manually. The individual roles might be as follows:

Mixing Pump

  • 2 people taking turns breaking sacks into mixing pump hopper
  • 1 person managing excess hose as the room is poured from the furthest point
  • 1 person holding the end of the hose, controlling placement of mixed material
  • 1 person on gauge rake
  • 1 person with smoother trowel

Hippo Drill/Barrel Mixers (2 mixing units)

  • 4 people for breaking bags, adding water, mixing and wheeling mixed material into place
  • 1 person on gauge rake
  • 1 person with smoother trowel

The pumping crew can mix and place approximately 200 sacks per hour. This equates to 1,300 sacks, or 32,500 square feet at 1/4” thickness, for an average day of 6.5 hours of actual pumping. The manual crew, at an average of five bags in 7 minutes per barrel, can mix and place 90 sacks per hour. This equates to 585 sacks, or 14,265 square feet at 1/4” thickness for the same 6.5 hours of pumping.

Using our example, a pumping crew can apply more than twice the square footage in a given day. This is accomplished while working at a smooth constant pace, placing consistently mixed material and not overworking personnel. Assuming a markup for SLU toppings of $.50 per square foot and a typical eight-hour day (6.5 mixing hours), this can equate to nearly $10,000 per day in added profits.

Schedule-related challenges common to most construction projects will likely always be present. But employing the latest pumping technology in SLU placement can help address these challenges. Jobs that once required a 10-person crew can now be completed with five people. In addition to solving schedule problems, that can lead to more efficient operations and greater profits.