Restoring sandstone window sills requires specialized care because sandstone is naturally porous and soft. Using incorrect materials like standard cement can trap moisture, leading to further decay or "spalling" where the stone surface flakes off.
Before starting any repair, the surface must be free of debris and organic growth. sandstone window sill repair
Do not use silicone, acrylic, or polyurethane sealers. These trap moisture, causing the stone behind the repair to explode in winter. or polyurethane sealers. These trap moisture