Laying and Leveling a Concrete Float
It's almost time for tile on the second floor. But first, the team must place the concrete float.
The upper level of Custom Design & Construction's Sheldon Street project will feature tile flooring throughout, and the first step in that process is to lay a concrete float over the plywood substrate. Today, Ismael Vera of FINELINES Construction brings his 19 years of experience to the installation job.
Vera and his crew cover the entire floor with black tar paper as a moisture barrier and install wire mesh to add durability and some texture for the concrete to bond with.
Regardless of how well a floor is constructed, it’s never going to be perfectly level thanks to variations and imperfections in lumber. To compensate, Vera pours lines of concrete, into which he sets wooden screed guides that he laser levels to ensure consistent thickness across the entire length of the floor. The end goal is to create separate areas, or "forms," that will retain the final poured concrete at a consistent thickness of ¾ inch.
Once that has dried, it’s time to pour the full float. Vera prefers a wet float to a dry-pack float, particularly over such a large area since it’s generally easier to level with a screed. You could use a 2x4 with a straight, smooth edge to screed, but Vera prefers an aluminum one specifically designed for this purpose, as it’s lighter and reliably straight.
While one assistant combines bags of plastic cement, sand, and water in a mixer out on the driveway, two more men carry a steady stream of 5-gallon buckets of the mixture into the house. They pour it into each section, and Vera methodically levels the mix with the screed. “It’s important to fill every bit of the area and work out any air pockets to avoid cracks later,” he explains.
This job calls for about 2 cubic yards of lightweight concrete, adding about 6,000 pounds of to the second floor—and that doesn’t even include the tile itself. Thank goodness for structural engineers.