When you use waterproofing paints to help stop seepage of water into basements, special treatment usually is needed at the lower parts of walls.

Q. Our cinder-block basement walls were painted on the inside with a waterproofing coating some years ago, but the paint has crumbled and peeled along the bottom area of the wall, and water seeps in there. How can I correct this? - E. Loeble.A. The extra vulnerability to seepage of the lower wall has caused deterioration of the coating. The lower part of block walls is the most difficult to seal because the water pressure is highest there. In some block walls, water can build up in the hollow parts of the blocks and eventually force its way inside, entering through pores or cracks in the blocks or at the joint of wall and floor.

To reseal this wall or seal a block wall that has never been sealed, start by cleaning the surface thoroughly. Use a stiff wire brush to remove loose material and check joints for loose mortar, which should be removed. Walls with white, powdery deposits of minerals, called efflorescence, will need treatment with a special cleaner/etcher such as Drylok Etch, sold at some home centers and building-supply outlets.

Cracks and holes in the wall, block joints or wall-floor joint should be patched with hydraulic cement, a special patcher sold under such brand names as Fast Plug and Waterplug. Follow directions on the container carefully.

To coat a wall, use a special waterproofing paint such as UGL Drylok or Thoroseal, which is sold in several colors. Use a coarse brush to apply a first coat that extends from the floor joint about 21/2 feet up the wall. Use the bristles to work the coating into pores and hairline cracks. Let the first coat dry thoroughly, and apply a second coat over the first, again using a brush but extending the second coat over the entire wall. A third coat, applied with a roller over the entire wall, can be used for extra protection.

Waterproofing paints have a powerful odor and must be used in a well-ventilated area. I also recommend wearing a respirator mask rated for use with paint solvents. Carefuly read and follow all cautions on the paint container.