Stone walls serve as a timeless method of marking boundaries, retaining livestock and protecting property. Landscape designers and gardeners now use stone walls for similar reasons and find that using mortar or simply dry stacking them without a bonding agent adds a natural look to gardens. Repairing damaged stone walls is not always easy, but it is well worth the effort to preserve your walled domain.
Clear away rubble and remove any loose stones. Clean off the old cement from the wall and from the loose stones by lightly tapping them with a hammer. Check for loose masonry and remove it. Don't worry about removing large chunks of cement that are firmly attached. Use a trowel to remove debris and then brush away the dust. Pile the loose stones, allowing for a clear and safe workspace.
Prepare the cement. Attempt to match the existing cement. Mix the ingredients until they have the consistency of oatmeal. Be careful when adding water or the cement may be too thin and unusable. Add sand until the colour appears the same as the existing cement.
Place a small amount of cement on a piece of wood and heat it with a hair dryer until it dries. Compare the sample to the mortar in the wall to see if the colour is a close match. Alter the colour by adding either dark or light coloured sand. Repeat this process until the cement matches the mortar in the wall.
Wet the stones of the damaged portion of the wall with a sponge to prevent the stones from leaching too much water from the new cement. This prevents the cement from cracking.
Fill in the open areas using a trowel and then replace the cleaned, loose stones. Use a wooden stick to fill in smaller areas and properly sculpt the fresh cement.
Fix the wall's base if it has been altered because of ground shifting. Use a shovel to establish a sound and even setting for the wall's stability and appearance. The footing needs to be about 7.5 cm deep and 20 cm wide, or both the depth and width of the existing wall. Allow for changes in the grade to retain the same height of the wall.
Lay the foundation stones in place to be sure the footing is wide enough. Save the better-looking stones for the visible portion of the wall. If the wall is constructed with cement, put some cement in the footing and firmly press the footing stones into place. Continue this process and be sure to check that the footing stones are level. Press them into place if needed or add more cement to get a level surface.
Stretch a string between two stakes to check that the borders are flush. Tap the stakes into the ground and continue to repair the wall. Longer stakes may be needed to check the level at different heights. Use varying amounts of cement to adjust the height of the rocks, but keep checking for a flush, even-sided wall.
Examine the face and dimension of each stone. Pay attention to the placement of each piece. This is a fine-tuned process of fitting and cleaning the joints between each stone.
Create a clean, relatively smooth joint by removing any excess cement while the cement is still slightly wet. Use a wire brush or a hand-held brush to create a brushed effect in the cement.
If the stone wall is constructed with a dry stacking method, or laid in place without cement, stack the loose rocks where they fit best. Be careful not to create an unbalanced or unstable wall. If the rocks don't fit, rebuild the wall or use a hammer to resize the stones. Do not damage stones that are hard to replace.
Use just enough cement mortar to fill in the spaces between the rocks. Avoid oozing and spilling cement on the wall face.
Wear eye protection when using a hammer to clean old cement from stones.