Troweling concrete floors is one of those tasks that requires patience and a little practice but can make the difference between a rough product and a smooth, professional looking one.
One thing to keep in mind is that you have a limited window of opportunity in which to work your poured concrete floor. Once it begins to set it is an unstoppable process, although it can be slowed down.
Some homeowners choose to use concrete, especially dyed, as their finished floor. In this case it is critical to get the best, smoothest finish as possible.
Screed and Darby
The first step after pouring the concrete is the screed. This involves using a straight and true 2” X 4” board to level the concrete to the top of your form. It also forces the larger aggregate (gravel) closer to the surface of the concrete. The 2” X 4” that you use should overlap the form by at least six inches on both sides.
To screed the concrete, begin at one end and proceed to the other with a sawing motion.
Next comes the Darby. No, that’s not a contractor’s name. The darby is tool used to smooth the concrete surface using overlapping arcs. Use only enough pressure to push down any lumps and fill any voids. On the surface. You can use a bull float with a pole for large projects.
Soon water will begin to form on the surface of the concrete. Before proceeding any further, wait until this water is reabsorbed into the concrete and pressing your thumb into the surface leaves a one quarter inch impression.
Edge and Groove the Concrete Floor
Now run your edger around the slab. The purpose of this step is to round off the edges which will prevent chipping in the future when the floor is dry and cured.
Now groove the cement every ten to twelve feet with a straightedge and a groover. Although you will trowel over the grooves next and cover them up, they will be present internally and will give the concrete a place to crack naturally if it has to.
Float and Trowel the Concrete
Now you can float the concrete floor. Use a magnesium float to further smooth the concrete. Sweep it across the surface in large arcs. The amount of pressure you have to apply depends on how hard the concrete has become. You may have to work faster at this point.
Finally, begin the troweling process. This is similar to floating but it just gets the concrete floor smoother and smoother on each successive pass. Use a steel trowel for this step.
Trowel it and let it dry a bit and then trowel it again. Keep the process up until you reach your desired level of smoothness. Three times is generally the maximum amount of troweling passes you will have to complete.