Cleaning stone wall mortar joints sustains the structural integrity and aesthetic quality of a wall socket. Over the years mortar joints can be a source of vulnerability from a stone wall, with mortar shrinkage, cracks and crumbling compromising wall strength and endurance. Cleaning dirt deposits and natural growth on the mortar shows problems inside the joint that the overlying contaminates hide, and prepares the surface for healing correction. Utilizing mechanical cleaning instead of chemical cleaning guards against pitting from the surrounding stone surface and detrimental pH changes inside the mortar joint.
Remove moss and lichen in the mortar joint working with a stiff nylon-bristled hand brush. Work from the surface to the base of the wall at horizontal movements to prevent detritus from falling onto formerly brushed joints.
Use a medium-powdered pressure washer to wash surface dirt out of the stone wall to ensure residual grime does not contaminate the joints through cleaning. Work in the same top down direction as you did at the prior step. Ensure you steer the pressurized flow of water just onto the stone face of this wall to prevent damage to the mortar joints.
Allow the stone mortar and wall joints to dry out before joint tooling. Abrade each mortar joint working with an oscillating power instrument equipped with the carbide attachment to remove shallow ingrained dirt or mold. Employing the assist handle attachment could prove beneficial, but is optional. Sweep along the joint with a soft hand brush to remove sanding dust.
Inspect the mortar joints for the incidence of more deeply ingrained mould, dirt and oily marks. Use the oscillating instrument to eliminate stained and moldy mortar, using controlled and uniform pressure over the problem joint.
Brush the mortar joints and stone surface of the wall with a soft-bristled hand brush to thoroughly wash tooling debris and dust off the stone wall. Inspect the clean mortar joints for signs of cracking and mortar shrinkage to prepare for additional repairs.