Repainting a stone wall can be a simple process, but it can also turn into a major project if the paint on the wall has chipped or the mortar in the wall has crumbled. The wall has to be prepared properly before you can apply new paint. The process is the same for both interior and exterior stone walls. Once the wall is cleaned and repaired, a primer and top coat are added. The project can be finished in a weekend.
Prepare the surface by removing chipped paint, loose mortar and soil. Use a heavy-duty detergent like TSP and a stiff wire brush to clean the surface. Exterior stone walls can be power washed to remove flaking paint and old mortar.
Clean mildew from the stone wall with a solution of three parts warm water and one part household bleach. Scrub mildewed areas and rinse with clean water before the solution has dried to prevent stains and streaks.
Seal cracks or places where the mortar has chipped with fresh mortar. Apply the mortar with a trowel and smooth it out with a damp sponge or rag.
Apply latex primer to the stone wall with a paint roller with a 3/8-inch nap. Primer will prevent water and stains from bleeding through the topcoat and will make the paint last longer.
Use a roller with a 3/8-inch nap to paint the stone wall with exterior latex paint (interior if you're working indoors). If the surface needs more than one coat, let the paint dry thoroughly. Use a small brush to apply paint in cracks or pits in the stone.
Clean brushes in water mixed with liquid fabric softener. Rent a power washer at your hardware or tool-rental store. Have tarps on hand if you're working outside and rain is possible.