Repairing a Stone Wall

• Maintenance of stonework requires attention to details. These tips that can help you keep your wall, walk, and patio in good repair.

• 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.

• 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.

• Choose the most gentle cleaning method that can handle the job. Start with water cleaning, the most gentle method, then turn to chemical-base cleaners or mechanical methods such as sandblasting only if you need to.

• Water increases damage to badly deteriorated mortar. Repair the mortar before cleaning with water.

• A pressure washer can be an effective cleaning method, but also may erode softer stones like sandstone.

• 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.

• Always test your cleaning agent in an inconspicuous spot before using it on the entire surface.

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.

Step 1: To repoint a wall of mortared fieldstone, first chip out cracked mortar with a 1-inch cold chisel and small sledgehammer. Brush away the loose material. Chip out the joint until you reach solid mortar.

Step 2: Then mist the joint lightly and push mortar into it with a small pointing trowel. Compress the mortar as much as possible. When the mortar has set up slightly, tool the joints to match the original.

If you repoint 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.