Concrete Floats

A concrete float is the tool that turns a rough, just-poured slab into something you can actually finish. Floating has to be done on virtually every concrete job after concrete is poured and leveled, with leveling usually accomplished with a screed. It’s the first real step in finishing. Get it wrong and the color won’t take, the surface won’t seal, and an outdoor slab can spall its top layer off in a few Montana winters.

Here’s what floating actually does to the mud. When done properly, floating pushes the aggregate down into the concrete and encourages moisture to rise, helping the concrete dry and creating a smoother surface. It consolidates the surface, fills the voids, and brings cream up where you need it. A float is not a trowel — the name float refers to a finishing tool that cement workers and plasterers use; it is sometimes called a trowel, but that is a different tool altogether. The trowel comes later for the hard, smooth finish. The float comes first.

The single most important thing to understand before you buy: float material isn’t cosmetic. It changes how the concrete behaves. Some floats seal the concrete while others tend to liven it up. As a general rule, magnesium and aluminum floats tend to seal, while wood and resin floats tend to open or bring more paste to the surface of concrete. That one fact drives every other decision on this page.

Float Materials and What Each One Does to the Surface

Pick your material first. Everything else — size, handle, reach — comes after.

Magnesium and aluminum are your sealers. The mag float is the staple of the industry. A mag float is simply a flat piece of magnesium or aluminum attached to a handle, and the tool allows the user to float concrete at his or her desired pressure and angle. The mag float rides what’s already there rather than cutting into it. Aluminum floats mimic the property of being able to help seal the surface of the concrete slab like a magnesium float can, but they simply do not have the durability that magnesium floats provide. So aluminum behaves like mag but won’t last as long.

Wood opens the surface up. Every concrete contractor should have a wood float in the toolbox. Wood floats are made of hardwood — mahogany or teak, for example — to resist wear and warping. They earn their keep when the pour gets ahead of you. Wood floats are particularly useful in those stressful instances in which concrete is setting up too quickly. They rough up the surface of concrete more than magnesium, almost forcing moisture to the surface while opening the surface up — increasing porosity — for surface applications of color, hardener, etc. The trade-off is honest: the wood float does the same as magnesium but costs a lot less, though they do warp and twist.

Resin is the wood float that won’t fight you. Resin floats were designed as a more resilient and wear-resistant alternative to wood floats. They perform virtually the same as wood floats — roughing the surface more than magnesium, drawing additional moisture to the surface, and opening up the concrete for surface applications. While some contractors continue to prefer wood floats, the choice between wood and resin seems to be a matter of taste.

Steel is for the hard finish, not the float pass. The steel float gives a hard smooth finish. More on why you keep that off your exterior pours below.

Laminated canvas-resin is the decorative-work specialist. The Kraft Tool version is built for colored and stamped jobs — the float’s 3/8-inch-thick canvas-resin material is long-wearing and does not seal the surface, which aids the decorative coloring process, with rounded corners to reduce float marks.

Material	What it does to the surface	Best fit
Magnesium	Seals; rides the surface; most durable	Inside slabs, everyday floating
Aluminum	Seals like mag, less durable	General floating
Wood	Opens surface, draws moisture, roughs it up; can warp	Outside flatwork, color/hardener, fast-setting pours
Resin	Acts like wood, more wear-resistant	Same as wood, longer life
Canvas-resin laminate	Long-wearing, does not seal	Decorative and colored work
Steel	Hard, smooth finish	Final troweling, not floating

Hand Float, Bull Float, or Darby — Match the Tool to the Job

Material settles texture. Tool type settles reach.

Hand floats are the small-job and cleanup tool. Screed floats and bull floats are designed for large flatwork jobs, while hand floats are generally used for smaller jobs and touching up the edges and hard-to-reach areas of large pours. Common hand float dimensions run around 12 inches long with widths in the 3-1/4 to 3-1/2 inch range, and you’ll see them with square or round ends. The round nose matters more than people think — a softened, raised corner is forgiving and won’t leave lines the way a sharp square edge does.

Bull floats get you out onto the slab without crawling on it. Bull floats allow the operator to reach far out onto a slab without having to get on the concrete with knee boards, because these floats consist of a long handle attached to a wood, resin, aluminum or magnesium float. The handle can measure anywhere from 4 feet to 16 feet long. Handles either snap onto the float or are threaded on, and a bracket assembly allows the angle to be adjusted so the float can reach the concrete surface at the angle needed for the job. Longer tool, flatter surface — the more blade running across the mud, the truer you keep it.

Darbies are the heavy-pressure cousin. Hand darbies are much like mag, wood, or resin floats, except they are longer, often tapered — wider at the tail, narrower at the head — and feature either two handles or a handle and a dowel, allowing the operator to use both hands. With a darby, the user can extend reach onto the concrete surface and apply more pressure when needed, for instance when concrete is setting too quickly or in applications that call for a stiff slump. Some darbies feature fixed handles, while others have adjustable handles.

There’s also a modern polymer hand float built for the tight stuff. Constructed from polymer material, it delivers lightweight handling, durability, and a non-stick surface, with rounded edges that prevent gouging or marking fresh concrete. It comes in 10”x5”, 16”x3”, 18”x3”, and 20”x3”. It’s best for 2-to-5 person flatwork crews doing edges, steps, curbs, and tight spots, and daily finishing on slabs, walks, drives, and patios after screed. It is not ideal for large open slabs where power trowels drive schedule and finish, deep control joints, or grinding and hardened slab work.

Inside Slab vs. Outside Flatwork — the Montana Freeze-Thaw Rule

This is where material choice stops being preference and starts being about whether your sidewalk survives.

For interior work, go magnesium. When it comes to placing an inside slab, magnesium floats are the best choice. A wooden float would be a poor choice on an inside slab, though many tradesmen used wooden bull floats on inside slabs before magnesium versions came along.

Outside is the opposite call. If you are placing outside flatwork or curbs, traditionally wooden floats and darbys have helped prevent spalling and have been the go-to floats for many years. There is no rule against using a magnesium or aluminum float on outside flatwork, but the porous nature of the wooden float helps prevent trapping moisture within a slab.

Why does that matter in this country? Because over-sealing an exterior slab is a slow-motion failure. For placing outside slabs, some building codes forbid the use of steel trowels or fresnos. The reasoning is that steel tools close in the cement so well that moisture absorbed into the concrete can become trapped and will eventually cause the aggregate within the slab to expand during freeze/thaw cycles, causing the top layer of the slab to pop off. Montana sidewalks, patios, and driveways cycle through freeze and thaw all winter long. A wood or resin float that keeps the surface open is the safer play on exterior flatwork. Seal it tight with steel and you’re trapping the very moisture that’ll spall it.

One exception worth knowing: when it comes to floating off the top of a foundation, the material of your float is inconsequential.

Handle Material — the Last Call, but You’ll Feel It All Day

The final consideration in selecting a float or trowel is the handle material. There are two main materials, wood or rubber, though some manufacturers make hand floats with hard plastic handles, which are not very common. Cork shows up too on some finishing floats.

The choice comes down to how your hand holds up under a long pour. It narrows down to comfort for most tradesmen. The rubber handles are designed to feel more comfortable as the tradesman leans weight onto their hands. But comfort has a catch. For many tradesmen, the rubber handles become too slippery as they sweat, while with wooden handles, your sweat actually helps you grip the handle better. There’s no wrong answer — pick the one that feels right in your hand. Manufacturers also offer an assortment of handle positions, with the handle attached farther forward or back on the float, so you can dial in the control point you like.

Frequently Asked Questions

What’s the difference between a float and a trowel? A float comes first and a trowel comes last. Floating pushes aggregate down and encourages moisture to rise, creating a smoother surface — it’s the first step in the finishing process. The trowel follows for the hard, smooth final finish. The float is sometimes called a trowel, but that is a different tool altogether.

Why use a wood float when magnesium lasts longer? Because they do different jobs. Wood floats rough up the surface more than magnesium, almost forcing moisture to the surface while opening the surface up for surface applications of color, hardener, etc. If you’re adding color or a hardener, or the concrete’s setting too fast, the open surface a wood or resin float leaves is exactly what you want.

Can I use a magnesium float on an outdoor sidewalk? You can. There is no rule against using a magnesium or aluminum float on outside flatwork, but the porous nature of the wooden float helps prevent trapping moisture within a slab. In a freeze-thaw climate, keeping the exterior surface open with wood or resin is the safer choice for slab longevity.

Why is sealing an outdoor slab too tightly a problem? Trapped moisture. Steel tools close in the cement so well that moisture absorbed into the concrete can become trapped and will eventually cause the aggregate to expand during freeze/thaw cycles, causing the top layer of the slab to pop off. That’s spalling, and it’s a real outcome on Montana flatwork.

What float should a homeowner buy to pour a backyard patio? For a patio — outside flatwork — lean toward a wood or resin float to keep the surface open against freeze-thaw. Hand floats are generally used for smaller jobs and touching up edges and hard-to-reach areas, while a bull float handles the broad sweep if the slab is large. Every concrete contractor should have a wood float in the toolbox.

Bull float or darby for reaching across a slab? Both extend your reach, but they work differently. A bull float lets you reach far out onto a slab without knee boards, with handles from 4 to 16 feet long. A darby extends reach and lets you apply more pressure when needed — for instance when concrete is setting too quickly or in applications calling for a stiff slump.