This story shows how to repair and paint a basement masonry wall.
Whatever your reasons for painting a basement wall -- to help waterproof it or simply to make it more attractive -- it's important that you first fix problems that are allowing water to migrate through the wall.
Condensation, the mildest form of water problem, doesn't originate on the outside. It forms when the cooler temperatures of water pipes and walls condenses the moisture from warm-weather air and leaves it on the surface. Increasing the ventilation, insulating the pipes, or installing a dehumidifier will relieve condensation.
To control seepage from groundwater, install new gutters or fix the existing ones and slope at least 4 feet of the soil away from the foundation so water runs away and doesn't seep through the walls. Sealing the interior surface of the walls with hydraulic cement and patching the holes can also cure some seepage problems. If neither of these methods work, consult a drainage specialist.
About an hour to prepare and paint a 6x8-foot wall, not counting drying time required for repairs and caulk
Wire brush, small sledge and cold chisel, trowel
Brushing walls, keying cracks, and applying liquid waterproofing agents
Check for moisture and eliminate outside seepage
Hydraulic cement, muriatic acid, waterproofing agent
Using a wire brush, remove as much loose mortar and paint as you can. Remove efflorescence (salts that leach to the surface of the wall and appear as a white deposit) with muriatic acid, following the manufacturer's instructions. Rinse the wall and let it dry.
Using a small sledge and cold chisel, key the cracks in the wall -- hold the chisel at an angle and undercut the edges of the crack so the bottom of the crack is wider than the opening. Keyed cracks help keep the patching cement in place. Vacuum the crack to remove the dust.