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Floating

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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Floating embeds the larger aggregate, smooths the surface and takes out small marks. The skill is timing.

I am a:

Tap your level and the boxes below open to the advice for you. Remembered on this device.

What it isSmoothing and closing the surface after screeding, and embedding the larger aggregate.
Your jobBull float right after strike-off, then wait for the bleed water to leave before anything else.
The hard ruleNever float over bleed water, and never add water or cement to the surface.
The checkThe sheen has gone and a footprint sinks in about 3 to 6 mm (1/8 to 1/4 in).

By the end you can

  • Bull float at the right moment and keep the float flat.
  • Read the bleed water and run the footprint test.
  • Name the defects caused by floating too early or too much.
  • Choose the right float for the surface.
Stop and read

Finishers kneel and lean over wet concrete for hours, which burns skin and strains backs. Wear waterproof alkali-resistant gloves, long sleeves, waterproof boots, eye protection and knee pads, and rinse splashes off quickly. Power floats are loud, so wear hearing protection. Keep clear of the machine edge and the cord or exhaust.

The big idea

Floating embeds the larger aggregate, smooths the surface and takes out small high and low spots. The key skill is timing. Too soon and you seal bleed water under the surface. Too late and the surface will not close.

The cement-industry flatwork rules say it plainly: finish only after bleeding has stopped, and never sprinkle water or cement on the surface.

Types of floats

  • Bull float: a wide float on a long handle, used right after strike-off.
  • Darby: a shorter hand-held version for smaller slabs.
  • Hand floats: magnesium or wood, for edges, steps, pads and small areas. Wood leaves a rougher surface that suits a broom finish.
  • Power float (pans or blades): for large slabs after the first set. Follow the machine maker for blade angle and timing.

Timing

  • Bull float right after strike-off, and finish before bleed water appears. Keep the float as flat as possible, so you do not seal the surface early.
  • Then wait. Do not do anything else until the bleeding has stopped. The wait depends on the mix and the weather, so test a small area.
  • Footprint test. The slab is ready for floating by hand or machine when your footprint sinks in about 3 to 6 mm (1/8 to 1/4 in).
  • Never float over bleed water. It can cause dusting, scaling, crazing, delamination and blisters.

Heat and wind dry the surface and shorten the window. Cold delays the set, so be patient. A fixed rule like "30 minutes" does not exist, because the mix and the weather decide.

Floating by hand

  1. Bull float once Right after strike-off, with the float flat. Overlap each pass and do not dig in the edges.
  2. Wait Leave the slab alone until the sheen has gone and the footprint test passes.
  3. Edge and joint Spade along the forms to break the bond, then edge and cut control joints at least one-fourth the slab depth, as the Slab Placement page covers.
  4. Float Use a hand float or a power float to embed the larger aggregate. Keep the float flat with even pressure, and blend the edges into the slab.
  5. Stop Do not over-float. Overworking brings up too much cream and seals the surface.

Exterior concrete

  • Exterior concrete is air-entrained. The cement-industry guide says never to steel trowel air-entrained concrete, so float it and then broom it.
  • Do not over-float. It seals the surface and traps water.
  • Keep the slope for drainage.
  • Leave a surface ready for a broom finish. A trade source says troweling is not usually required for exterior work.

Common mistakes

  • Floating while bleed water is present
  • Sprinkling water on the surface
  • Overworking and bringing up cream
  • Digging in the edges
  • Poor timing with a power float
  • Steel troweling air-entrained concrete
Pro note

Water on the surface means wait. If the sheen is still there, you cannot float yet. Test with a footprint before you commit a machine.

Weather note

Hot weather and wind dry the surface and shorten the window, so protect the slab and be ready. Cold delays the set. Rain ruins a floated surface.

What the inspector looks at

Surface finish, flatness, and any scaling or dusting are checked.

✅ Check yourselfTap a question
When do you bull float?
Right after strike-off, before bleed water appears on the surface. Keep the float as flat as possible so it does not seal the surface too early.
Bleed water is still on the surface. Can you float?
No. Never float while there is bleed water. Wait until it has gone, or you risk dusting, scaling, crazing, delamination and blisters.
How do you know the slab is ready for floating by hand or machine?
The footprint test: a person's footprint sinks in about 3 to 6 mm (1/8 to 1/4 in).
It is windy and the surface looks dry. Can you sprinkle water on it to make floating easier?
No. Never sprinkle water or cement on the surface while finishing. It can cause dusting or scaling.
What is the rule for steel troweling air-entrained concrete?
Avoid it. Exterior concrete is air-entrained, so float and then broom.
What does floating actually do?
It embeds the larger aggregate, closes the surface and takes out small high and low spots left by the screed.
🧰 Gear for this stepMust-haveRent itNice to have
  • Must-haveFloating (hand tools):
  • Rent itFloating (machine): a power float (pans or blades) for large slabs
  • Must-haveReach and access:
  • Must-haveEdges: an edger and a hand float for blending
  • Must-haveConsumables: fuel or charged batteries for power floats, and clean water for cleaning tools (never for the surface)
  • Must-havePPE:
👷 Who can do thisTap your level
Home DIY
A capable owner can bull float and hand float a small slab if they wait for the bleed water to leave. Power floats on a large slab are best left to someone who has run one.
Laborer or helper
Move kneeboards, keep tools clean and stay off the slab until you are told it will carry you. Do not add water to the surface, ever. Tell your lead if the sheen is still there.
1st-year apprentice
You can bull float and hand float under supervision. Learn to read the bleed water and the footprint test, and to keep the float flat.
Apprentice, 2nd to 4th year
Bull float and hand float under supervision. Read the bleed water, run the footprint test, keep the float flat and overlap passes. Tell your journeyperson if the surface is tearing or the sheen is not leaving.
Journeyperson
You own the timing: when to bull float, when to wait, when the slab will carry a power float. Stop-work triggers: floating while bleed water is on the surface, or any water or cement being added to the surface.
Lead hand or foreman
Assign who floats and who tests the footprint, and enforce the triggers: floating over bleed water, and anything sprinkled on the surface. Plan crew size to the slab, because the window is short in heat and wind.
Contractor or business owner
Price enough finishers and a power float for large slabs. Dusting and scaling show up after the crew has left and are expensive callbacks. Ask your lawyer or insurer about callback and warranty terms.
Starting a new business
Learn the timing before you quote finishing work. Rent a power float, subcontract large slabs until your crew is proven, and keep photos of every slab. Confirm callback and warranty terms with your lawyer and insurer.
By Province:

The technique is the same across Canada. What changes is the code edition and local rules. NBC Part 9, Section 9.3 sets the concrete minimums, including air entrainment for exterior steps and garage floors. I did not re-verify provincial code editions on this pass, so confirm yours with the local authority.

See Canada by Province for the full comparison.

Sources:
  • CIP 14, Finishing Concrete Flatwork (NRMCA Concrete in Practice, US: bull float timing, bleed water, footprint test 3 to 6 mm, no water or cement on the surface, air-entrained concrete not troweled)
  • Concrete Care: Residential Flatwork Guide (cement-industry guide: air-entrained concrete never steel trowelled)
  • Float types and power float use come from general trade practice and were not checked against a source. Follow the machine maker for blade angle and timing.
  • CSA A23.1 was not read directly. Provincial code editions were not re-checked.

Last reviewed October 2026. General information, not engineering or legal advice.

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