Concrete Step Repair: How to Fix Cracks and Broken Edges

What do you need to fix cracked concrete steps?

A flexible, UV-stable crack kit, dry silica sand and a few hand tools. Steps sit outside in full sun and move with the seasons, so a rigid filler cracks loose and a filler without UV protection breaks down.

How do you fix a crack in concrete steps?

Open up thin cracks, clean and dry them, pack them with sand soaked in urethane, then top them with a polyurea filler. This is the method in the UV slab kit’s instructions, and it works on cracks up to 1/4 inch with flush edges.

Here’s how to fix a crack in concrete steps with that kit:

1. Check the edges

   Lay a straightedge across the crack. If one side is higher, or the crack is wider than 1/4 inch, skip to the section on steps that need more than a filler.

2. Open up thin cracks

   For cracks 1/8 inch wide or less, the kit’s instructions say to grind the crack out to 1/4 inch wide and 1/4 inch deep so the filler has room to grip. Wider cracks skip this step.

3. Clean and dry the crack

   Vacuum out the dust, loose concrete and weeds. The instructions say it’s critical that the crack be dry, so wait for a dry day and a dry surface.

4. Prime with urethane

   Wet the inside of the crack with the kit’s urethane.

5. Pack in sand

   Pour dry silica sand into the crack until it’s 1/4 inch below the surface.

6. Soak the sand

   Saturate the sand with more urethane and let it set for about 30 minutes.

7. Top it off

   Fill the last 1/4 inch with the polyurea filler. It’s thin and levels itself.

8. Scrape it flush

   Scrape any overflow flush with a razor scraper, then keep off the step until it’s ready for traffic.

How do you repair a broken step edge?

Chip back to solid concrete, brush on a bonding agent, set a board as a form and pack in a polymer-modified patch. This is the fix for a broken step edge or a missing corner, the damage people trip on most.

1. Chip back to solid concrete

   Use a cold chisel and hammer to knock off everything loose or cracked, with safety glasses on. Stop when you hit concrete that doesn’t flake.

2. Clean and dampen

   Brush and vacuum out the dust. Dampen the old concrete if the bonding agent or patch instructions call for it, without leaving puddles.

3. Set a form

   For a missing edge, screw or brace a board against the riser so its top lines up with the step’s tread. For a small chip, you can shape the patch by hand.

4. Brush on the bonding agent

   Coat every surface the patch will touch.

5. Pack in the patch

   Press the patch in firmly while the bonding agent is still tacky, slightly overfilled. Build deep breaks in layers if the product says to.

6. Shape and texture

   Trowel the top flush with the tread and round the corner slightly. Finish with a broom or float so it isn’t slick.

7. Cure it

   Keep the patch from drying fast by covering it with plastic, and take the form off when the product says it has set.

Timing matters most at step 5. A Kansas State University study for the U.S. Department of Transportation found that with cement grout bonding agents, after 15 minutes, bond loss can be expected (opens in a new tab). Its epoxy bonding agent performed best, as long as the patch went on while the epoxy was still tacky.

The same study notes that the durability of a patch is directly related to the bond strength (opens in a new tab) between the repair material and the existing concrete. That’s why the cleaning and bonding steps aren’t optional on a thin edge.

For the materials, look for a polymer-modified vertical concrete patch, which stays in place on a riser without slumping, and an epoxy bonding agent made for bonding new concrete to old.

Which repair do your steps need?

Match the damage to the fix before you buy anything. Cracks, broken edges and flaking surfaces each need a different product, and steps that have moved need a different kind of help.

How long before you can walk on repaired steps?

About an hour for a filled crack in mild weather. The polyurea top takes light foot traffic in 30 minutes and full traffic in 60 minutes at 70°F, according to its data sheet, and the concrete needs to be at least 50°F when you apply it.

Cold slows every cure. For the edge patch and bonding agent, follow the times on their labels.

What mistakes make a step repair fail?

Most failures come from moisture, a thin crack that was never opened up, or a patch that went on too late. Each one has a simple fix.

• Filling a damp crack. The kit’s instructions call a dry crack critical. Wait for a dry spell, not just a dry-looking surface.
• Skipping the grinding on a thin crack. Filler can’t get into a crack 1/8 inch or narrower, so it bridges over the top and peels off. Open it up to 1/4 by 1/4 inch first.
• Leaving a ridge. Filler left above the surface is a trip edge on a step. Scrape the overflow flush before it sets.
• Patching over a dried bonding agent. The Kansas State study found bond loss can be expected (opens in a new tab) after 15 minutes with cement grout bonding agents. Pack the patch in while the bonding agent is still tacky.
• Working in the cold. The polyurea data sheet calls for concrete at 50°F or warmer. Pick a mild day.
• Filling steps that have moved. If the steps tilted or pulled away, the crack will open again. Fix the movement first.

When do concrete steps need more than a filler?

When they’ve moved. Steps that have sunk, tilted toward the house, or pulled away from the wall are sitting on soil that settled. Filling the crack or the gap hides the movement but doesn’t stop it.

Uneven steps are also a fall risk. Building codes limit how much step heights can differ: a city of Stillwater, Oklahoma code guide says riser height may not vary more than 3/8” in a flight of stairs (opens in a new tab). If one step now sits noticeably higher or lower than the others, it’s past patching.

Your options for steps that have moved are lifting them back into place, rebuilding them, or replacing them. A concrete contractor can price those. If the steps pulled away because the house or a foundation wall moved, or there are cracks in the wall behind them, have a structural engineer look first.

Why do concrete steps crack and crumble?

Mostly from water, freezing and salt. Steps are thin, exposed on several sides, and get more salt than almost any other concrete around a house.

• Freeze-thaw. The NRMCA explains that water in saturated concrete expands as it forms ice and this causes stresses (opens in a new tab) that flake the surface. Step edges and corners are thin, so they break first.
• De-icing salt. The same NRMCA sheet says heavy use of de-icers increases potential for scaling (opens in a new tab), and to never use ammonium sulfate, ammonium nitrate or magnesium-based salts on concrete.
• No isolation joint. The NRMCA lists stairs among the places where slabs need isolation joints (opens in a new tab). Steps poured tight against a walkway or the house have nowhere to move, and crack where they meet.
• Settled fill. Steps often sit on backfill next to the foundation, which can settle for years after the house is built.

The why concrete cracks guide covers these causes in more detail.

How do you keep repaired steps from cracking again?

Keep water and salt out of them. Once the repair cures, seal the steps with a penetrating sealer, and go easy on de-icers.

The NRMCA recommends sealing the surface with a commercial breathable sealer (opens in a new tab) to protect concrete from freeze-thaw damage. It also says calcium chloride and sodium chloride (rock salt) are acceptable de-icers when used in moderate amounts, and suggests clean sand for traction.

Shovel before you salt, so you need less. Keep downspouts from dumping water onto or next to the steps.

The sealing after crack repair guide covers which sealer to use over a repair and how long to wait.