Fix a cracked concrete path by cleaning, undercutting and filling the crack with mortar, then curing it properly.
AB-01Assess the crack and plan the repairCheck the width and depth of the crack. Hairline cracks under 5mm can be filled with a ready-mixed masonry crack filler straight from the tube. Wider cracks or crumbling edges need cutting back and repairing with sand-and-cement mortar. If the same crack keeps reappearing each year, that usually means ground movement, and any repair will only be temporary.
AB-02Gather tools and protect the areaLay a dust sheet or plastic sheet either side of the crack to catch debris and stop mortar splashing onto the lawn or borders. Put on safety goggles and gloves before breaking out any concrete. Keep pets and children away from the work area while tools are out.
AB-03Break out and undercut the crackUse a bolster chisel and club hammer to open the crack slightly and undercut the edges, so it's wider at the bottom than the top. This gives the new mortar something to grip. Remove any loose or crumbling concrete back to a firm, solid edge - a ragged edge is fine and actually helps.
AB-04Clean the crack thoroughlyBrush out all loose material, dust and debris with a stiff wire brush. Flush the crack with water from a hose or watering can to remove fine dust. Leave it damp if going straight in with mortar, or let it dry if you're using a bonding agent that needs a dry surface - check the label.
AB-05Apply a bonding agent for a stronger repairBrush a coat of PVA bonding agent, or a proprietary concrete bonding solution, onto the clean, damp concrete edges. This helps the new mortar grip the old concrete instead of just sitting on top of it. Skip this step if your repair mortar or filler already contains a bonding agent - check the tub or tube first.
AB-06Mix and apply the repair mortarMix a sand-and-cement repair mortar - roughly 3 parts sharp sand to 1 part cement - or use a pre-bagged repair mortar and follow the pack instructions. Mix to a firm, not sloppy, consistency. Press the mortar firmly into the crack with a pointing trowel, working it right down to the bottom to avoid air gaps, and slightly overfill it.
1 bag · Ready-mixed concrete repair mortar (5kg bag)
AB-07Level and finish the surfaceDraw a wood float, or the flat edge of the trowel, along the repair to level it flush with the surrounding path. Match the existing texture by lightly dragging a stiff broom across the wet mortar in the same direction as the rest of the path. Wipe away smears from the surrounding concrete with a damp sponge before they dry.
AB-08Cure the repair properlyCover the repair with plastic sheeting or a damp cloth for at least 24 hours so it doesn't dry out too fast, which causes cracking. Keep foot traffic off it for 24-48 hours and vehicles off for 3-4 days, checking the mortar pack for exact times. In hot or windy weather, dampen the repair lightly with a watering can once or twice a day for the first two days.
AB-09Tidy upSweep up leftover debris and dispose of old concrete rubble responsibly - most councils won't take rubble in general waste bins, so check your local tip's rules. Clean tools with water before the mortar sets hard on them. Store any leftover bagged mortar somewhere dry, as damp will ruin it.
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