Rising damp occurs when masonry walls absorb water from the ground due to capillary action. It can rise over 1m depending on the wall material and ground conditions. Diagnosing the cause is important - it may be rising damp, rain penetration, condensation, or leaks. Treatment involves improving drainage, replacing damaged damp-proof courses, and allowing walls to dry before replastering. New methods using chemical injection or nanotechnology are being researched to more effectively treat rising damp.