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Float

A tool used to smooth and compact the concrete surface after screeding

A float is a flat tool used to smooth and compact the concrete surface after screeding and before final finishing. Floating embeds aggregate slightly below the surface, fills small voids, and creates a smooth, dense surface ready for additional finishing steps or texturing.

Why It Matters

Floating is the critical middle step between rough screeding and final finishing. Skip it and you'll have a coarse, porous surface with visible aggregate. Over-float and you'll bring too much paste to the surface, creating a weak layer prone to scaling and dusting.

For DIY projects, proper floating technique and timing make the difference between professional results and obvious amateur work. Working too early (while bleed water is present) causes serious surface defects. Working too late (after concrete stiffens) is difficult and leaves trowel marks.

Technical Details

Types of floats:

Bull float: Large float (3-8 feet long) mounted on a long handle, used immediately after screeding on freshly placed concrete. Smooths the surface, fills depressions, and levels ridges while concrete is still very plastic.

Hand float (magnesium or wood): Smaller handheld float (typically 14-18 inches long) used after bull floating when concrete has stiffened slightly. Wood floats produce rougher texture; magnesium floats create smoother surface.

Fresno (power float): Large walk-behind float (30-48 inches) used on large commercial slabs. Not typically needed for residential work.

Floating technique:

Bull floating (5-30 minutes after screeding):

  • Work in sweeping arcs across the slab
  • Push float away with handle raised slightly (leading edge up)
  • Pull back with handle lowered slightly
  • Overlap passes by half the float width
  • Don't overwork—2-3 passes maximum
  • Purpose: embed aggregate, level surface, close surface voids

Hand floating (when concrete supports finger pressure with slight imprint):

  • Use flat, sweeping motions with slight pressure
  • Overlap strokes
  • For wood float: rougher, slip-resistant texture
  • For magnesium float: smoother surface, preparation for troweling
  • Don't bring up excess paste (indicates overworking)

Timing is critical:

  • Too early: Disturbs concrete, brings excessive water to surface
  • Too late: Difficult to work, leaves marks
  • Right time: When bleed water disappears and surface accepts light finger pressure

When to skip hand floating:

  • If broom finish is desired, broom directly after edging/jointing
  • If coarse texture is acceptable, bull float may be sufficient
  • Bull Float - Large long-handled float used after screeding
  • Finishing - Overall surface preparation process
  • Trowel - Tool used after floating for smooth finish

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