How to Smooth Concrete Finish

How to Smooth Concrete: Wet vs Dry Methods

Smoothing concrete requires different tools and techniques depending on when you're working: while the concrete is wet (during placement) or after it's cured (dry). This guide covers both methods and when to use each.

Smoothing Wet Concrete

Working with wet concrete gives you the best results and is the preferred method. You have a limited window (typically 1-2 hours) to achieve the finish you want.

Step 1: Magnesium Float (Initial Smoothing)

The magnesium float is used first to push down aggregate and create initial smoothness.

When to Use

After screeding (leveling) and while concrete is still very wet (first 30-60 minutes).

Technique

• Hold float flat against surface
• Move in circular or figure-8 patterns
• Apply light pressure—don't press too hard
• Work systematically across the surface

What It Does

• Pushes down rocks and aggregate
• Brings "cream" (fine cement paste) to the surface
• Creates initial smoothness
• Removes high spots

Step 2: Steel Trowel (Final Smoothing)

The steel trowel creates the final, smooth finish. This is done after the magnesium float, when the concrete is stiffer.

When to Use

After magnesium float, when concrete has "set up" enough to support the trowel (typically 1-2 hours after placement, depending on conditions).

Technique

• Hold trowel at a slight angle (10-15 degrees)
• Move in smooth, overlapping passes
• Apply firm but not excessive pressure
• Work when concrete is "plastic" (not too wet, not too dry)

Multiple Passes

Professional finishers typically make 2-3 passes with the steel trowel:

• First pass: Removes float marks, creates initial smoothness
• Second pass: Further smooths, removes any remaining imperfections
• Third pass (optional): Creates very smooth, burnished finish

What It Does

• Creates smooth, dense surface
• Burns the surface (compacts the cream layer)
• Removes all tool marks
• Creates professional finish

Smoothing Dry Concrete

If you missed the window for wet finishing, or if you need to smooth existing rough concrete, you'll need to grind and polish.

Step 1: Diamond Grinding

Diamond grinding removes material to smooth the surface.

Tools

• Angle grinder with diamond cup wheel (small areas)
• Walk-behind concrete grinder (large areas)
• Diamond grinding discs (coarse to fine grits)

Process

1. Start with coarse grit (30-40 grit) to remove high spots
2. Progress to medium (80-120 grit) to smooth
3. Finish with fine (200-400 grit) for final smoothing
4. Always work wet (keep surface wet while grinding)

Step 2: Polishing

After grinding, polishing creates a smooth, finished surface.

Tools

• Orbital sander with polishing pads
• Or angle grinder with polishing attachments
• Progressive grit pads (400, 800, 1500, 3000)

Process

1. Start with 400 grit to remove grinding marks
2. Progress through 800, 1500, 3000 grits
3. Each grit removes scratches from previous
4. Final polish creates smooth, sometimes glossy finish

When to Use Each Method

Wet finishing (float + trowel):

• During new concrete placement
• Best results and easiest method
• Must work within time window

Dry finishing (grinding + polishing):

• Existing rough concrete
• Missed the wet finishing window
• Need to smooth cured concrete
• More labor-intensive but effective

Common Mistakes

1. Troweling too early: Concrete too wet, creates problems

2. Troweling too late: Concrete too hard, can't achieve smooth finish

3. Over-troweling: Brings too much water to surface, weakens it

4. Skipping magnesium float: Can't achieve proper smoothness with trowel alone

5. Not using proper tools: Wrong tools create poor results

The Bottom Line

For wet concrete: Use magnesium float first to push down aggregate and bring cream to surface, then steel trowel for final smoothness. Work within the 1-2 hour window when concrete is plastic.

For dry concrete: Use diamond grinder to remove material and smooth, then polish with progressive grits to achieve final finish. More labor-intensive but effective for existing concrete.

Wet finishing is always preferred—it's easier, faster, and produces better results. But if you miss that window or need to smooth existing concrete, grinding and polishing will work.

Need professional concrete finishing? Contact Local Concrete Contractor. We have the tools, experience, and techniques to achieve the smooth finish you want.