# How do you finish concrete?

Finishing concrete runs in a fixed order: screed the surface level, bull float it, wait for the bleed water to disappear, then edge, cut joints, float, and trowel or broom. Timing is everything. Working the surface while bleed water is still present ruins the slab.

## Short version

- Screed, then bull float immediately. Both happen while the concrete is still plastic.
- Stop and wait. Nothing else happens until the bleed water has evaporated off the surface.
- Edge, cut joints, then float and finish. Broom exterior slabs; hard-trowel interior slabs only.
- Never work bleed water back in, and never sprinkle dry cement or water to make finishing easier.
- Start curing as soon as the finish will not be marked, and keep it moist 3 to 7 days.

## What is the correct order of concrete finishing steps?

Finishing follows a sequence tied to how fast the concrete sets, and skipping or reordering steps causes most surface defects.

| Step | Tool | When |
|---|---|---|
| Screed | Straightedge or screed board | Immediately as concrete is placed |
| Bull float | Bull float or highway straightedge | Right after screeding, still plastic |
| Wait | Nothing | Until bleed water is gone |
| Edge | Edging tool | After bleed water leaves |
| Joint | Groover or saw | After edging, or saw-cut within hours |
| Float | Hand float or power float | Surface firm enough to walk with light marks |
| Finish | Broom, or trowel for interiors | Last pass before curing |
| Cure | Water, blankets, or curing compound | As soon as the surface will not mark |

Screeding strikes the concrete off level with the forms and establishes the plane of the slab. Bull floating immediately afterward pushes the coarse aggregate down, brings paste up, and closes the surface, which is the single most important step for a durable finish.

Each step exists to do something the previous one could not. Screeding sets the plane, bull floating closes the surface, floating levels and opens it, and the final pass sets the texture. Skipping one does not save time; it moves the problem to the finished slab.

Everything after bull floating waits on the concrete, not on your schedule.

## When is concrete ready for the next finishing step?

Concrete is ready for edging and floating when the bleed water has evaporated and the surface no longer glistens. Bleed water is the water that rises as heavier solids settle, and it is a normal part of the process.

The working test is to step on the slab. When your boot leaves an impression of roughly a quarter inch and does not sink further, the concrete is ready for the next pass. Before that point, any tool you drag across the surface works water back down into the top layer.

That waiting period varies enormously. A cool, humid, overcast day can stretch it to hours, while a hot windy afternoon can eliminate it almost entirely. Air content, cement type, admixtures, and slab temperature all shift the timing, which is why a fixed clock time is useless.

In hot or windy conditions, the surface can dry faster than bleed water rises, and plastic shrinkage cracks open within hours. Windbreaks, sunshades, fog misting, or an evaporation retarder all help. Typical flatwork runs a 3 to 5 inch slump, and resisting the temptation to add water beyond that keeps both strength and finishing behavior predictable.

## What is the difference between floating and troweling?

Floating and troweling do opposite things to the surface. Floating with a wood, magnesium, or composite float embeds aggregate, levels minor ridges, and opens the surface texture slightly, leaving it gritty and mildly rough.

Troweling with a steel blade compacts and densifies the surface into a hard, smooth, closed layer. Each successive trowel pass with the blade at a steeper angle produces a harder, glossier surface.

Order matters and cannot be reversed: float first, trowel afterward, and only if the slab is meant to be smooth. Every slab gets floated; not every slab gets troweled.

For a broom finish, float the slab, then draw the broom across it. For an interior warehouse or garage floor, float and then run multiple trowel passes.

The critical rule with both is not to overwork the surface. Excess passes bring fine material to the top and leave a weak layer that dusts or scales later.

## Why do exterior slabs get a broom finish instead of a smooth trowel finish?

Exterior concrete gets a broom finish for two reasons: traction and delamination. A hard-troweled surface becomes dangerously slick when it is wet or icy, so any walking surface exposed to weather needs the texture a broom leaves behind.

The second reason is more technical and more expensive to get wrong. Exterior concrete in freeze-thaw climates is air-entrained, which builds a system of microscopic air bubbles that give freezing water somewhere to expand. Hard-troweling air-entrained concrete seals the surface while air and bleed water are still trying to escape, and the trapped layer separates from the slab beneath. That defect is delamination, and it shows up as hollow-sounding patches that break away in sheets months later.

Broom the slab perpendicular to the direction of travel and drainage, so the grooves shed water and give shoes something to grip. Drag the broom in one continuous pull per pass and rinse it as you go, because a broom loaded with paste leaves ragged, uneven texture.

## When do you cut control joints?

Cut control joints during finishing with a grooving tool, or saw-cut them within the first several hours while the concrete is still gaining strength but hard enough not to ravel. Concrete shrinks as it dries and will crack; joints decide where.

Spacing follows the slab thickness. The convention is 2 to 3 times the thickness in inches, converted to feet, so a 4-inch slab gets joints every 8 to 12 feet and a 6-inch slab every 12 to 18 feet. Keep panels close to square, and avoid long narrow panels, which crack across the middle.

Joint depth should be about 25 percent of the slab thickness. A joint cut too shallow does not create a weak plane, and the slab cracks somewhere else instead.

Isolation joints are a separate matter. Anywhere a slab meets a foundation wall, a column, or an existing slab, a compressible isolation material lets the two move independently.

## What do you do after the finish is done?

Start curing as soon as the surface is firm enough not to be marked. Curing is what actually builds strength, and NRMCA's Concrete in Practice guidance calls for a minimum of 3 to 7 days of moist protection, with the longer end for cooler weather and higher-strength mixes.

Methods include water ponding, wet burlap kept continuously damp, curing blankets, plastic sheeting, or a liquid membrane-forming curing compound. Plastic sheeting can cause mottled discoloration on decorative work, so plan around that if appearance matters.

The first 24 hours matter most, since that is when the surface is most vulnerable. A slab that dries out in sun or wind during that window ends up with a weak, dusty top layer no amount of later care fixes.

Keep traffic off. Foot traffic generally waits 24 to 48 hours and vehicles about 7 days, both industry convention rather than published standards.

## Common mistakes

- **Finishing while bleed water is on the surface** — working that water back in raises the water-cement ratio at the top and produces a weak layer that dusts and scales.
- **Sprinkling dry cement or water to ease finishing** — both destroy the surface, one by creating a weak skin and the other by thinning the paste.
- **Hard-troweling exterior air-entrained concrete** — the sealed surface traps air and bleed water and delaminates in sheets a few seasons later.
- **Cutting joints too shallow or too late** — the slab picks its own crack location, usually diagonally across the middle of a panel.
- **Walking away once the finish looks good** — without curing, the surface never develops the strength the mix was designed for.