1. Scrub especially dirty basements with a cleaning solution. If a concrete or concrete-block surface is especially dirty, add detergent and a quarter cup of ammonia to a bucket of warm water and brush the solution over the surface with a stiff nylon brush. (Never use a metallic brush; metallic fibers can get trapped in the concrete and rust.) For really stubborn dirt, get extra kick by adding trisodium phosphate to the wash water. TSP is available at hardware stores. Rinse with a hose and let dry. Use a shop vacuum to remove excess water.
2. Freshen a smelly basement with bleach. Mildew that takes up residence in a basement gives off an unpleasant, musty odor. Open windows to let in air, use fans to improve air circulation, and install a dehumidifier to remove moisture. To get rid of the fungal growth that’s the source of the smell, mix up a brew of 1 to 2 ounces of household bleach per quart of water in a spray bottle. Spray the walls and floors with the solution and scrub them with a nylon-bristled brush.
3. Treat the floor with bleaching powder. An easier solution for the floor in a smelly basement is to sprinkle it with chlorinated lime (bleaching powder; sold in the supermarket’s laundry section). Let it sit there, soaking up the bad odor and microorganisms that cause it, for a day, then sweep or vacuum it up. Dispose of the sweepings outdoors. If the odor persists, seal the concrete with concrete sealer.
4. Ditch the efflorescence. The white powder that sometimes accumulates on the concrete walls or floor of a basement is efflorescence, soluble salts that remain when water seeps through concrete and evaporates. Clean it off with a rigid, nylon-bristled brush or a wet rag or mop. If it returns, you may need to waterproof your basement walls.
5. Remove rust stains. Do away with a rust spot by sprinkling it with dry cement and rubbing with a small piece of flagstone (the kind used to pave patios). The combination of dry cement and stone acts like pumice and should remove the stain.
6. Give your basement floor a makeover. Tired of your dull gray concrete basement floor? Give it a new look with a waterproof stain. The stain and other supplies you need are all sold at home centers. The process is simple:
• Scrub the floor with trisodium phosphate (TSP) or a similar strong alkaline cleaner-degreaser and rinse with a hose.
• While the floor is still wet, sprinkle it with muriatic or phosphoric acid and scrub with a stiff-bristled nylon brush for a minute or so. This roughens the surface so that it will accept the stain better. After 20 minutes, hose the floor three times to rinse away all the acid and stop the etching action.
• When the floor is dry, use a short-nap paint roller on a long handle to apply the stain in 3-by-3-foot sections. Let the stain dry for 24 hours before walking on it.