Floating

Summary

Floating - is the process of further settling aggregate and allowing fat to rise to the surface in a concrete floor. It also helps to remove slight imperfections in the surface flatness.

Technical Information

Floating is an essential step in finishing a concrete floor. It leaves the floor with a layer of fat above the aggregate, which is essential for other finishes, such as a trowelled or textured finish.

It is important to time floating correctly. A simple and effective indicator of whether it is time to float the concrete is how deep an imprint is left by a boot’s heel. If the imprint is more than a few mm deep, the concrete is not yet ready to be floated and if the heel leaves no imprint, it is too late for floating to be effective.

Mis-timing floating could have the following consequences for the slab surface:

If a slab is floated before bleeding has finished, there is an increased risk of delamination.
If the slab is floated whilst the concrete is still too soft, the surface can be torn up.
If the slab has hardened too much before floating begins, the floating will be ineffective and the surface imperfections will remain.

The following equipment can be used to float a concrete floor slab:

Power float – A power trowel fitted with float blades or a pan. The best way to float large areas quickly.

Bull float – A T-shaped handheld tool consisting of a long handle and a float blade (up to 3m in width).

Hand float – A float blade with a handle on the back. Suitable for small areas and for places that can’t be reached by a power float in larger projects, such as panel corners.

Too much power floating can lead to a darkening of the surface of the slab, known as burnishing.