Q: We live in a two-family attached brick house that has a flat roof. The upstairs apartment is much colder during the winter, and warmer during the summer. We are planning to affix insulation to ceilings of the top floor apartment and then drop the ceilings to hide this insulation, but want to know if this will bring about enough of a change in the temperature differences to be worth the effort.

A: Adding insulation will definitely help - if you add enough. It should have a rating of at least R-19, but more would be even better. Have you investigated the possibility of having loose fill blown into the space between the roof and the ceilings, instead of adding it onto the surfaces below? This might be less expensive and more satisfactory in the long run.

Q: We recently put down vinyl asbestos tile on the concrete floor of our basement. Periodically we get water in the basement through the walls (got up from the floor). This is easily cleaned but I notice some of the tiles have loosened because water apparently is seeping down through the joints between the tiles. Is there a sealer I can apply to the tile floor to prevent water from seeping down between the seams and loosening them?

A: I doubt if any sealer or other coating will work in a case like this; wax will serve as well as anything else. You should take steps to cure the water seepage problem anyway, because it can cause other problems. Some slight seepage may be taking place through the floor where you cannot see it (under the tiles). If you can't come to any other solution, perhaps you ought to look into installing a sump pump.

Q: We bought a house in which part of the roof is completely flat. As a result we have frequent leaks - evidently from cracks in the tar. Is there some way to reduce the frequency of this problem?

A: There are various fibrated roof coatings you can buy for application on flat roofs such as yours. These will temporarily seal small cracks and minor leaks, but it sounds to me as though you are about ready for a new roof on that part of your house.