You may be tempted to replace damaged stone with synthetic stone made from epoxy or cement-based materials. Such imitation stone is less expensive. Though the patches may look good at first, they will become conspicuous with further exposure to the elements and ultimately mar the appearance of the wall. We’ll walk you through common stone wall repairs, including replacing a popped stone, rebuilding a damaged wall, repairing stone mortar joints, and more. Editor’s tip: To ensure the longevity of your wall, look to the landscaping. Climbing plants pose no danger to hardened mortar, but roots disturb footings and tendrils take hold in cracks. Plant life in the wrong places displaces stones or bricks, blocks rainwater runoff, and hides other damage. To remove plants, cut the main stem above ground level and treat it with a product recommended by your local extension service. However, residues of some weed killers can cause spalling on some stone surfaces. If stone-faced steps are worn, you may be able to reuse them by turning them over. A pressure washer can be an effective cleaning method, but also may erode softer stones like sandstone. Keep in mind that water increases damage to badly deteriorated mortar. Repair the mortar before cleaning with water. Steam cleaning is an effective method for removing embedded soil and poses less risk than sandblasting. Sandblasting is a method of last resort. A poultice of absorbent material mixed with a solvent can remove many chemical stains without damaging the stone. Keep the poultice on the stain as long as necessary to remove the stain. As a rule of thumb, always test your cleaning agent in an inconspicuous spot before using it on the entire surface. Editor’s tip: If you repair masonry with mortar that doesn’t match the original, it will really stand out. Matching the tint of existing mortar takes some experimenting and patience. You can’t tell what the new mortar will look like until it has dried. Mix up the mortar in several batches and spread out thin amounts to dry. Pick the dried color that best matches the original. Editor’s tip: It’s important to pack mortar tightly. Otherwise, the wall will be more susceptible to erosion. Soil erosion is often the cause of a toppled wall section. This is a problem that does not usually show up for many years. To repair the damage, remove stones from the damaged area and at least two stones wider. Dig a 6- to 8-inch trench where you have removed the stones. Fill the trench with gravel a little at a time and tamp it as you go. Rebuild the section of wall. The gravel will allow water to drain under the wall without washing out its support.
