Q: We have lived in our house for six months and although we had no problem during the summer, after the recent heavy rains and show we have had water seepage through the basement floor. The former owner had sealed the cracks between the floor and walls, but this doesn't seem to help now. We want to finish the basement, but can you suggest how to eliminate the dampness problem without having to waterproof from the outside?

A: Water coming up through the floor is the toughest of all basement problems to cure. The only sure method of doing the job from the inside is to dig a trench around the perimeter by chopping away the concrete floor down to the top of the footing. Then lay drain tile (performed pipe) in this trench and either connect this to a properly installed sump pump, or to an exterior drainage point such as a street sewer (in communities where this is permitted).

Q: My back porch and steps were painted with gray enamel. Since they were slippery when wet, we added a special sand to the last coat, but this left black marks. Now we want to use flat paint, such as a stain. Can this be applied over the sand and enamel paint?

A: You cannot apply stain over paint. You can, however, buy flat-drying floor paints - these are generally latex (water-thinned) type. They will adhere over your present paint, and they dry quite dull.

Q: My basement floor is dry and dusty, and has a tendency to sand off every time I sweep it. It has never been painted. I would like to cover it with vinyl tile. Is there any special preparation required first?

A: This will depend to some extent on the type of tile you buy. You should use the adhesive recommended for that brand and type of tile. Sometimes these recommend a sealer, but not usually. Use a vacuum to pick up as much of the dust as possible, then follow the manufacturer's directions for applying the adhesive.

Q: Last summer I used masking tape on the windows to protect the glass while I was painting them. I did not remove the tape for about a week, and as a result the removal of the tape was very difficult. In addition, there are now ugly adhesive marks on the glass. Is there a solvent that will remove these marks?

A: Acetone will work, but it will remove paint as well, so you will have to keep it away from the moldings and trim. Rubber cement thinner, which is sold in art supply stores, will work too, and it will not harm most paints.

Q: The porcelain in my sink and tub is brownish yellow. Cleaners and bleach do not work. Can the sink and tub be painted?

A: Yes, if you use a two-part epoxy paint. Just be sure to clean the surfaces thoroughly and rinse off all detergent and soap residue carefully. Then follow the directions on the can exactly. Once painted, remember the coating will probably have to be renewed periodically.

Q: I have to install a humidifier in my house, but we have baseboard hot water heating, so I cannot install one of the kind that hook onto the hot-air duct of a furnace. The house has three levels, without the basement. What type of humidifier can you suggest?

A: There are many brands of portable, console-type humidifiers sold in appliance stores which you can use. These have to be filled by hand from a pitcher or pail, but they will handle several rooms from one location, so most homes need only one on the bedroom level. There are also permanent, central units that can be installed in houses that do not have hot air heat. These fit in the basement or in a utility room and usually are connected to a water line so they fill automatically.A single large duct through the floor or one of the walls carries moist air to the other rooms. Your local heating and air conditioning man should be able to give you more specifics on these units.