DIY Masonry Crack Repair

• Concrete and Mortar Defined
• About Masonry Coatings
• Painting Masonry
• About Masonry Damage

To repair cracks in foundations, walls, slabs and walkways first be sure the movement that caused the crack has been stabilized. If the movement causing the crack is minimal, it may be possible to fill it with masonry caulk that will move with the crack for a permanent seal. If the movement is more severe it may be necessary to reinforce the footer or foundation to stop movement. Multiple cracks, like those pictured, are an indication of major problems with the stability of the structure.

Repairing Cracks

Prepare the crack for repairs using a putty knife or screwdriver to scrape out all loose material. Hose out the crack if possible, if not, use a shop vac or compressed air to remove all debris. Soak the crack completely using a spray bottle when working inside and a hose on exterior cracked surfaces. Saturate the masonry well just before applying the mortar patch. If a crack dries out before the mortar is applied, soak it again. You can't get it too wet but if it becomes too dry the new patch will not bond well.

Mix a batch of repair mortar using one part portland cement and three parts very fine sand. Use the finest sand you can get from your local home store to make your patch mortar bond well with the old masonry. Mix the cement and sand well and then add water to make a thick mud that holds its shape.

Use a putty knife to press the mortar into the crack starting a one end. Press mortar into the crack until it starts to ooze back out. Do this along the entire length of the crack and then go back to scrape off the excess. Finish the repair by applying a smooth coat of mortar to level the masonry surface along the crack. As you work keep the masonry surface around the crack damp with a spray bottle of water if necessary. After the repair is completed use a spray bottle to keep the patch damp for about 3 days until it cures.