Q: Our house is built on a sloping lot so that part of the basement opens to the outside. The concrete floor of this basement is covered with tiles that are in good condition and have never raised or lifted. Now we want to cover part of the floor with a different title, but the dealer we contacted to do the job is against putting the new tiles on top of the old. He says the old ones must come up even though they are perfectly smooth. Is this necessary?

A: If the old tiles are firmly stuck, and if they are smooth and not ridged or unevenly worn, it is often possible to put new floor tiles down on top of the old ones. It depends to some extent on the type of tile you select. Check the manufacturer's specifications after you have selected the tile.

but remember that when you put new resilient tile down on top of old tile, there is the possibility of indenting since there is another resilient surface under the new one. Also, if there are any irregularities in the old floor, even though scarcely noticeable now, they will be much more evident a few months after the new tile is placed on top.

Finally, if the old tile should start lettin go in some places it may lift and take the new tiles up with it in the future.

Q: My house has aluminum window frames that are pitted and badly discolored. Nothing I do seems to improve their appearance. I have tried aluminum jelly cleaners but this was a lot of work and did very little to change things. Is there something you can suggest?

A: Aluminum cleaners generally work well on oxidized aluminum but when the metal is badly pitted, they cannot do much to correct that condition. As I see it, you have two choices. One is to rub the metal down with fine steep wool to remove the pit marks and discloration, then immediately coat the metal with clear lacquer or a good grade paste wax (that will have to be renewed periodically). The second alternative is to paint the metal frames with a good quality exterior trim paint in the color of your choice. The metal will still have to be cleaned and rubbed with steel wool to minimize the pitting before the paint is applied.

Q: I am planning to build a wood deck next to my house, using all pressure-treated lumber. The deck will be supported on 4-by-4 posts that will be sunk into the ground so about 24 inches will be below ground. Is there anything I can cover or paint onto these posts that will help give them a longer life and resist rot better?

A: If you are using pressure-treated lumber from a reputable producer of this material, the wood will have already been treated with the best preservative to resist rot. Nothing you can add will improve much on this. However, for longest life you should not bury the posts. Instead, pour concrete footings for the below-ground area and have them stick up slightly above ground. Then set your wood posts on top of the footings, securing them with bolts or anchors that are buried in the concrete as you pour it.

Q: The concrete floor in my basement gives off a lot of dust. I have been told that painting would eliminate this, so I plan to do that. However, sometime in the future I want to finish the basement and put some kind of tile down. Will tile stick if I have paint on the floor?

A: It will if you use a latex floor enamel, but not if you use an oil or alkyd base deck paint. Be sure the paint is adhering tightly before you cover it (scrape off any that is peeling or flaking) and make sure the paint is at least two months old.

Q: My house has a roof made of cedar shingles that are about 10 years old. The edges of these shingles seem to be crumbling so I want to put something on them to preserve them. Do you know of a coating I can apply that will help preserve or waterproof them?

A: Most large paint stores and lumberyards stock shingle stains that are made for use on cedar shingles, and some that are specifically formulated for use on roof shingles. Applying two coats of one of these would undoubtedly help preserve your roof. If you want a clear preservative, any of the colorless wood preservatives and sealers sold for use on exterior wood could be used.