Trowelling 101: How to Effectively Use a Trowelling Machine

If you've ever worked in construction, you're familiar with a trowelling machine. If you've been at it long enough, you may even be a real artist with a trowelling machine. 

It takes years and practice to finesse a trowelling machine around a slab of concrete like a pro. Being counted among the greats is no small feat. 

But every troweller has to start somewhere. 

For those of you who are a little newer to the trowelling game, here's a guide to Trowelling 101. It's everything you need to know to get started with a trowelling machine. 

Why Trowel At All?

After you pour the concrete slab, you need to trowel it to consolidate the cement. This helps remove excess water from the concrete, smooth and level the surface.  It finishes the concrete to the desired shine and hardness.

It also addresses laitance

What Is Laitance?

Laitance is a layer of fine particles that rise to the top of the cement if too much water is added or the cement is not properly cured. 

This laitance layer needs to be removed from newly poured concrete floors. It is a major cause of floor failure. Laitance is a weak, friable layer that can destroy all your hard work if it's not dealt with properly. 

Choosing the Right Trowelling Machine

There are a couple of options for trowelling machines. Typically, the size of the concrete slab dictates what kind of trowelling machine you need for a job. 

Walk-Behind Power Trowel 

A walk-behind machine is exactly what it sounds like. You walk behind the machine and push it. It is powered so you aren't shoving the weight of the entire machine. 

A walk-behind trowel will get the job done if you're leveling less than 90 square meters of concrete. You will want blades that are in the 24-36 inch range. 

Ride-On Trowel 

The other option is a ride-on trowelling machine. This trowel option is great on jobs larger than 90 square meters. 

You'll want to choose a blade in the 36-inch to 48-inch range for the open floor. When navigating corners or edges, you'll likely want a smaller 24-inch blade. 

Is Your Concrete Ready to Trowel?

You can't trowel wet cement. You need to let it sit for at least a couple of hours before you start the process of trowelling. 

You need to trowel when the concrete is firm enough to support weight, but not yet fully hardened. 

Here's a quick way to test. Step onto the concrete and then step back off. Take a gander at your print. If your shoe print is less than 1/4-inch in depth, fire up the trowelling machine. 

Kinds of Blades and Pans

The blades and pans are the attachment which directly interacts with the concrete. There are several kinds of attachments that can be used for different jobs. 

Float Pans and Float Blades

Float pans are large metal discs that attach to the bottom of the trowel machine. The large diameter of the pan helps distribute the weight of the trowel machine which makes it "float" on the concrete. 

A float pan is the best option in the early stages of trowelling because it won't sink in before the concrete finishes curing. The act of floating the concrete helps smooth out bumps and fill in divots.

Float blades are an alternative to float pans. They are wide flexible blades that can be attached to your other blades to help "float" the trowelling machine in the early stages of concrete setting. 

Like float pans, float blades help distribute the weight of the machine and prevent the machine from digging in. 

Either is a good option for the first pass over the concrete. You should run the blades flat and the trowelling machine at a lower speed when using float blades or pans. 

Finishing Blades

After you go over the concrete with float blades or pans, you'll need to swap for finishing blades in order to finish and seal the porous concrete. 

Finishing blades are much more rigid than float blades. Unlike float blades, you want to pitch the finish blades and run the trowelling machine at full speed. 

Combined Blades 

Instead of changing out float blades halfway through for finishing blades, you can opt to use combo blades for the entirety of the project. 

Understanding Pitch

Pitch determines how much of the blade is in contact with the concrete.

Float pans and float blades should be set at zero pitch, meaning they are flat against the cement surface. 

Combo blades should be set at zero to very slight pitch while they are being used to float the concrete. As the slab hardens, you can increase the pitch of the combo blades to finish the concrete. 

Finishing blades are used after float blades, so they should be set at a higher pitch. This allows the angle of the blade against the concrete to finish the slab. 

As a rule of thumb, always start with less pitch than you think and increase as needed. If you start with too high a pitch, you risk digging into the concrete and ruining the surface. 

Steering the Trowelling Machine

The only way to get good at operating a trowelling machine is to simply do it. There is a nuance to steering that can only be learned hands-on. Here are the basics:

Operating a Walk-Behind Power Trowel

A walk-behind trowel is typically petrol-powered, so make sure there is enough petrol in the engine. Also, check the engine and gearbox oil before you get started trowelling. 

A walk-behind trowel is easy enough to steer. If you've ever used a floor buffer, you should have a good working knowledge of the mechanics.

Pull up on the handle to steer to the left. Push down on the handle to steer to the right. 

Operating a Ride-On Trowel 

Steering a ride-on trowel takes a little more finesse.

The driver has two control levers that steer the power trowel. The left lever operates the backwards and forwards motion on the left side of the trowel. 

The right lever is more complicated. It functions in a cross pattern, meaning it goes right/left as well as forward/backward.  

To move directly forward, push both levers forward. To move directly backwards, pull both levers back. Pushing forward on the left lever and to the right on the right level moves the trowel machine at an angle. 

The degree to which the right and left lever are used simultaneously creates a wide range of movements. An experienced operator can navigate around obstacles, in any direction and cover the entirety of the slab. Moving smoothly in a ride-on trowelling machine takes practice. 

Ready? Set? Trowel!

Now that you have the basics of operating a trowelling machine down, get out there and start practicing. You can't become a great without sweat and tears. 

But remember to always use safe operating practices in order to reduce risk and avoid injury. Be sure to wear hearing, eye and hand protection. 

Contact us with questions or if you need help picking the right trowelling machine for your job!