A power trowel is used to create a level, smooth finish on a large, flat area of concrete, such as an interior floor, or a poured patio slab for a deck. They use single or multiple blades that rotate in a safety cage. They measure from 24 to 48 inches long and come in three types: floating, finish, and combined. You can use a pushable concrete power trowel or riding model based on the size of your job. Follow the steps before for the proper procedures so you can use this tool to the best of your ability.
Step 1 - Choose a Power Trowel
To level a small area of under 1000 square feet, choose a pushable power trowel with 24 to 36 inch trowel blades. Get both float and finish trowel blades, or select a combined blade, to smooth the concrete in one series of passes.
For large areas over 1000 square feet, a riding power trowel will help you finish quickly before the concrete sets too firmly. Use blades that measure 36 to 48 inches in size. For corners, switch to a 24 inch blade. Choose separate float and finish blades, or a combination trowel blade.
Step 2 - Test the Concrete Before Troweling
Have the concrete poured a few hours before using the power trowel. Make sure it is firm enough to support you and the power trowel by doing a footprint test; step onto the slab and measure the imprint depth. If the imprint is 1/8 of an inch deep or less, the concrete is ready for troweling.
Step 3 - Float the Concrete to Remove "Hills and Valleys"
Use the trowel with float blades or combined blades to level the concrete on your first pass. Floating reduces bumps (hills) and fills in the hollows (valleys).
Run the machine at 3/4 speed with the blades flat to keep the weight of the machine evenly distributed and avoids digging into the concrete. This speed of rotation will also prevent splatters of still-damp concrete being thrown forward into the machine's path. Overlap each pass by 1/2 the length of the trowel blades as you traverse the poured plate.
When you finish floating the entire slab once, turn the power trowel at 90 degrees to your first rows. This crossover floating technique enables you to finish missed spots.
Step 4 - Finish the Concrete to Seal, Close, and Polish
Change to finish blades or continue with the combined trowel blades to finish the surface, sealing the porous material. Run the power trowel at its top speed this time with the blades fully pitched downward onto the concrete. This will give the highest pressure on the slab. Make as many passes at right angles as desired to get a matte, light gloss or gleaming finish.
Wear safety goggles, ear protection, and boots with a steel toe and soleplate while operating any type of power trowel. Always use heavy leather work gloves and turn off the power trowel before clearing or changing blades.
When operating the power trowel, reduce speed when turning corners to avoid tipping the machine. Also, cordon off the area, for safety and to prevent marring the concrete.