A Step-by-Step Guide to Professional Concrete Floor Finishing

Table of Contents

• Determining the Right Time to Start Concrete Floor Finishing
• Concrete Floor Finishing Techniques and Patterns
• Troubleshooting Concrete Floor Finishing Issues
• Applying Broom and Slick Finishes for Exterior Concrete
• Conclusion and Key Takeaways for Professional Concrete Finishing

Determining the Right Time to Start Concrete Floor Finishing

Knowing when to start the concrete finishing process is crucial for achieving a high-quality floor slab. The concrete needs to be at the right consistency - not too wet or too dry. Doing the finishing too early can cause issues like trapped bleed water leading to delamination. Doing it too late makes it very difficult to properly seal the surface.

There are a couple ways finishers judge when the slab is ready. The classic method is the finger test - pushing fingers into the slab to check plasticity. Usually waiting until fingers sink no more than 1/4 inch is ideal. Using tools like a flowing pan float or combination blades at this stage helps open up the slab and flatten aggregate below the surface.

The Finger Test for Concrete Consistency

As shown in the video, pushing fingers into the slab is a simple way to check consistency. The concrete should only sink around the fingers by about 1/8 inch before it's ready for power floating. If fingers sink more than 1/4 inch, it's likely still too wet for finishing. However, finger tests can be inconsistent if concrete sets up unevenly. One spot may pass the finger test while another area is still too wet. So finishers need to carefully check multiple areas before starting.

Avoiding Trapped Bleed Water When Finishing Concrete

Bleed water rising to the top of the slab needs to evaporate before power troweling begins. Otherwise it can get trapped right under the surface and lead to delamination or blisters. When bleed water is still present, continue floating gently with combination blades or a pan float to open up the slab. Avoid walking on areas with bleed water. Allow time for it to dry up before troweling over those spots.

Concrete Floor Finishing Techniques and Patterns

Once the slab is ready, the first phase is flattening the aggregate below the surface. Float pans, shoes, and combination blades excel at this due to their large surface area. Maintaining consistent overlapping pass patterns is key.

The finisher starts floating perpendicular to the previous pan passes. Slow speed and flat blades prevent digging into the cream. As the slab sets up, the finisher can increase pitch for tighter consolidation. Switching to finishing blades in the later stages burns the cream for a polished look.

Using Float Pans, Float Shoes, and Combination Blades

Float pans have the largest surface area and do the best job bridging over low spots while cutting down high areas. Float shoes attach to regular blades for added surface area versus just combination blades alone. The goal is to flatten aggregate under the slab while leaving an even cream layer on top. Keeping blade pitch low and using slower speeds prevents gouging the cream in these early passes.

Pitching Concrete Finishing Blades Properly

Pitching the blades higher consolidates the cream layer more with each pass. This helps tighten and smooth the surface. When floor is nearly ready, increase pitch for a final tight burnishing. But pitching too much too soon can scrape away the cream layer unevenly.

Troubleshooting Concrete Floor Finishing Issues

Pay close attention to the slab while finishing to catch any problem areas. Look for holes, tears, irregular textures and address them immediately before the concrete hardens.

If the slab starts setting faster than expected, be prepared to increase pitch and speed to keep up. Falling behind on sealing the surface can lead to an uneven finish with exposed voids.

Applying Broom and Slick Finishes for Exterior Concrete

Outdoor concrete like a patio needs extra traction from a broom finish to prevent slipping when wet. Apply a light broom texture after floating and troweling.

For interior slabs and polished concrete, continue troweling with finishing blades to fully consolidate the cream. This burns the surface tightly for a slick, smooth finish.

Conclusion and Key Takeaways for Professional Concrete Finishing

Achieving a flawless concrete floor finish requires careful timing, technique, troubleshooting skills and the right tools. Key takeaways include:

• Knowing when to start floating based on the finger test and bleed water evaporation

• Using the proper blades and patterns for each finishing stage

• Adjusting pitch and speed as the slab sets up

• Catching and fixing any defects before the concrete hardens

• Choosing the appropriate final finish based on the environment

FAQ

Q: What is the best concrete floor finishing equipment?
A: A float pan provides the largest surface area for flattening concrete aggregate initially. Float shoes or combination blades are good alternatives.

Q: When is concrete ready for power troweling?
A: You should start power troweling when concrete reaches a consistency that allows trowel blades to sink no more than 1/8 inch.

Q: What causes visible trowel lines in finished concrete?
A: Trowel lines become visible if you do not properly seal the concrete surface on each pass. Slow down and ensure full coverage when needed.

Q: Why avoid walking in bleed water when troweling?
A: Walking in bleed water can trap it underneath the surface, causing delamination and weakness in the slab.

Q: How do you fix pinholes and voids when finishing concrete?
A: You must fill pinholes and voids properly while concrete is still plastic. It becomes very difficult once concrete starts to harden.

Q: What type of broom finish should you apply on exterior concrete?
A: A light horsehair broom finish provides grip while still yielding an attractive look on exterior slabs.

Q: Should concrete finishing blades be pitched up or down initially?
A: Keep blades very flat (pitched down) during initial passes to flatten the aggregate layer beneath the surface.

Q: How can you speed up and slow a walk-behind power trowel?
A: Lift the trowel handle to increase speed and lower the handle to decrease speed.

Q: What causes concrete to dry fast and 'blow up'?
A: Direct sunlight exposure causes concrete to hydrate rapidly, blowing up the setting process.

Q: What is the best practice for broom finishing concrete?
A: Wait until the surface is almost too tight, wet it to bring up cream, then apply the broom finish.