What’s the Difference: Concrete Hand Floats
Wood, resin, aluminum, or magnesium?
Once a slab has been poured, screeded, and bull-floated (see “Creating a Curved Concrete Walkway” in FHB #221), it’s time for hand floats.
A bull float, which is used to smooth 95% of a slab, has a tendency either to pull a small amount of concrete away from the edges of the slab or to push concrete toward the edges. A hand float is used to level and smooth these areas so that they match the rest of the slab. Floats also can be used around obstacles, such as pipes and drains, where more precision is needed.
These tools are made in several shapes and sizes, and from four materials. According to Marshalltown Company product manager Jim Bowie, it’s a common misconception that price is the deciding factor; each material’s effect on the concrete should be considered.
A steel trowel should never be placed on the concrete until all bleed water has evaporated. This tool compresses the top layer of the slab, which adds strength to the surface and gives the slab a durable finish. If used too soon, though, a steel trowel closes the pores of the concrete and traps water below the surface, which would more than likely cause the top layer to delaminate.Prices shown are for Marshalltown Company products.
A wood float is the least expensive option, but it isn’t durable over the long haul. Because a wood float constantly soaks up bleed water, is dragged over a rough concrete surface, and is hosed down after use, it loses its edge over time. This creates a rough, fuzzed-up surface that pulls and drags at the surface of the concrete rather than smoothing it. This effect sometimes can be useful, though, especially when working with really stiff concrete or concrete that is setting up too hard. Wood also is preferred when applying shake-on color hardeners, which need to be worked into the top surface of the slab. Although redwood is a common material choice in this category, some companies also sell floats made from hard species, such as Marshalltown Company’s Xtra-Hard, which is made from jarrah, a wood denser than teak. They cost a few dollars more than redwood.
144D (16 in. by 3-1⁄2 in.): about $15
Laminated-canvas resin floats have an extremely dense “waffle” surface that gives the concrete the same slightly rough texture as a wood float. The advantage to paying twice the cost of a wood float is that you get a much more durable tool. Canvas resin doesn’t soak up water, so it won’t fuzz up after repeated use on wet concrete and after being hosed off at the end of a job.
4526D (16 in. by 3-1⁄2 in.): about $29
Aluminum floats have many of the same characteristics as magnesium floats, but they are roughly 30% heavier and 30% stronger. Like magnesium, aluminum opens the pores of fresh concrete, allowing bleed water to evaporate. Although many contractors prefer a certain float for each type of concrete, aluminum has no real specialty or added benefits in any common situation.
MF380R (15-1⁄2 in. by 3-1⁄8 in.): about $22
Although they are slightly weaker than their aluminum counterparts, magnesium floats are lighter and are the most popular choice among professionals. Magnesium smooths the surface of fresh concrete and opens the pores for proper evaporation, all without pulling the surface like a wood or resin tool. Most magnesium floats are extruded or cast. Extruded floats are made by pushing molten magnesium through a die (think Play-Doh), so the floats are the same profile from end to end. Molten magnesium can be cast into any shape desired. Some contractors like a float with more knuckle room, and a cast float can be made with small pedestals that raise the handle for more room.
145D (16 in. by 3-1⁄8 in.): about $32
Photo: Rodney Diaz
For more info:
- Creating a Curved Concrete Walkway
- Build a Concrete Walkway Series: Smoothing the Surface
- Placing a Small Concrete Slab