Water gets into a basement by leakage, seepage, or condensation. Problems caused by seepage and condensation are usually easier to fix than leaks. Use a step-by-step approach when waterproofing. Start with the easiest job. If that doesn’t solve the problem, proceed to more difficult remedies. Simple remedies Wrap sweaty cold-water pipes with fiberglass insulation. If the walls sweat in humid weather, use a dehumidifier.
Check the roof gutters. If they are broken or clogged, repair, replace, or unclog them. Basement drains may be clogged with dirt or tree roots; hire a service to unclog them. If earth has settled around the house, regrade the earth to slope away.
Damp or weeping walls that are without cracks can sometimes be treated. Wait for a dry period or use a dehumidifier to get the walls dry. Scrub concrete or cinder block with trisodium phosphate (TSP) or mild muriatic acid. If the walls get wet only occasionally, a latex masonry sealer paint, applied as directed, may solve the problem. For persistent dampness, try a two-part epoxy masonry sealer. Follow the same procedure for a damp concrete floor.
Advanced remedies – Install a drain or drainage system to combat continual basement flooding. A sump pump may help. (See Sump pumps.) If your basement floor is dirt or gravel, consider having a concrete floor poured on top of a plastic liner.
Repair large cracks or gaps in basement walls from the outside if they are above ground level or easily accessible with a little digging. Use mortar. When the patches are dry, coat them with pargeting (a thick bituminous solution) or a vinyl spray. If you cannot reach the crack on the outside, you can apply quick-cure concrete patching to the inside for a temporary repair, but it will leak eventually.
If these measures fail, you may have to resort to the tedious and expensive job of waterproofing the exterior foundation walls. Remove the plantings and excavate the earth around the foundation down to the footings. Clean the walls and coat them with pargeting. Finally, replace the earth and plantings.