Microtopping mixing and application techniques are similar to those for overlays, but a couple differences can cause heartbreak – or at least major frustration. Microtoppings have a longer pot life in the bucket but a relatively short dry time, and a little goes a long way.
Self-levelers and stamped overlays require mixing large volumes of material quickly so you can apply them expeditiously, but it’s best to mix microptoppings as needed because a small volume covers a larger area. One 5-gallon pail at a time is usually sufficient. When roughly two-thirds has been applied, the next bucket can be mixed and ready to go.
Some microtoppings require adding liquid polymer to the dry cement while others are single-component products that only require water. When mixing two-component systems, pour the required amount of polymer into the bucket and then add the integral coloring agent (if using). Mix with a paddle drill until a uniform color is achieved and then add the dry ingredients slowly to prevent clumping. Mix for no more than two minutes to three minutes.
For projects ranging from 300 square feet to 1,500 square feet, one to two people mixing is usually sufficient. With two workers, one can mix with the paddle drill while the other dumps the dry ingredients into the bucket.
Usually one person can effectively work a small area. For larger areas, mix a couple batches at a time and have several people troweling to get the material down without delay. Microtoppings dry quickly, so you don’t want big piles of freshly mixed material on the floor waiting to be troweled unless you have sufficient labor to work swiftly. Dump from the bucket only what you’re able to trowel or squeegee right away.
Match Tool to Technique
Application tools and techniques vary depending on microtopping type, project size, and look you’re trying to achieve.
Standard application tools are a handheld steel trowel with square or rounded edges or a “magic” trowel (a soft rubber squeegee 12 inches to 22 inches long). To avoid repeating lines, I recommend using a random trowel motion in different directions rather than sweeping half arcs. The important thing, though, is to go with a troweling style that produces the final look you’re after.
On large jobs, it’s often more expeditious to use a rubber squeegee attached to a long handle. Many types are available specifically for installing microtoppings. Some have tapered or rounded edges; others are square. Some are made of flexible rubber while others are more rigid. Experiment to find the best tool for the material you’re working with.
With most trowel- or squeegee-applied toppings, you’ll need to put down at least two coats. Check the technical data sheets for recommended time frame between applications. Usually a minimum drying time of 2 hours between each successive lift is required. You don’t have to re-prime between lifts if you apply the next coat within the specified time frame.
Semi self-leveling microptoppings are applied in one lift rather than two or more separate coats, but finishing is more complicated. The first step is to apply the material to a depth of about 1/8 inch with a gauge roller or a gauge rake set at a depth of 1/8 inch. These tools spread the topping evenly while ensuring uniform depth, but they’re not designed to move large volumes. To facilitate spreading, pour in a uniform ribbon rather than dumping the topping in one area. (It’s best to have one person pour while another uses the gauge roller.) Try to spread it in sections 2 feet to 4 feet wide, making sure to avoid cold joints (distinct lines that form between sections that dry at different times).
Semi self-leveling microptoppings usually require at least one troweling and, depending on the degree of polish you’re trying to obtain, sometimes two. Begin the first within 10 minutes of spreading, depending on ambient, substrate, and topping temperatures. (The warmer the conditions, the faster the material sets.) Again, I like to use a random trowel motion to smooth and level the surface.
If you want the look and feel of smooth, hard-troweled concrete, a second troweling is necessary. Timing varies depending on project size and temperatures. I find the most opportune time is when 75% of the surface bleed water has evaporated, leaving patches of damp areas on the surface. Be sure to kneel on spiked kneeboards or wear cleated shoes to avoid leaving foot or knee prints in the fresh topping.
Even if you’re as meticulous as possible with the trowel or squeegee, you can end up with distinct lines in the topping left behind from your tools. If this isn’t the desired effect, use a palm sander or orbital sander to smooth out imperfections once the material dries (or the next day). On large areas, use a buffing machine with a 100-grit sanding screen.
The One Thing You Must Never Do
It’s imperative to keep air from moving across the surface during application, especially with semi self-leveling products. This applies whether you’re working inside or outside. On one interior flooring project, 1,500 square feet went down beautifully – except in an area where I’d left two doors open on either side of the building, where the cross draft caused the microtopping to skin over. Fortunately, I discovered the problem in time to avert disaster. In a situation like this, lightly mist the surface with water to provide enough cream for finishing. If you’re working in a newly erected building that’s not completely enclosed, you may need to erect temporary windbreaks of plywood or plastic at doorways and windows.
Next time: coloring options and decorative effects.
