QI have a treated-wood deck and have had all kinds of trouble with finishing it. I let it dry out, the way the builder told me, and then applied a semi-transparent stain. When there was mildew, I scrubbed it off. I haven't been able to keep any finish on it since. What can I do? -- A. Falkson

A It's not clear what the specific problem is with your deck, but here are some general tips:

* Don't apply any finish to a deck without thoroughly cleaning it first. If there is mildew on the surface and it is not eliminated, it will quickly reappear. Deck cleaners that will kill mildew are sold at most home centers.

* Don't try to apply a new type of finish without removing an existing finish. When switching finishes (from semi-transparent stain to a clear finish, for example), start with bare, clean wood. A good deck stripper is StainStrip, by the Flood Co. (www.floodco.com or 800-321-3444).

* Many finishes for wood decks simply do not hold up for long. Despite claims by manufacturers, some finishes deteriorate after a few years, and some do not last even that long. For an eye-opening lesson on deck finishes, see the July 2005 issue of Consumer Reports magazine, which has conducted ongoing tests of many deck finishes. The top-rated finishes held up for three years, but some had poor resistance to mildew and color change. Semi-transparent stains, which are often recommended for wood decks, did not hold up as well as the best opaque (solid-color) stains. Only one clear finish lasted three years. Some well-known brands performed so poorly they were dropped from the tests. Every owner of a wood deck should check these ratings.

Some deck owners adopt a different strategy. Wood decking (the floor boards) and railings are replaced with composite material, made from ground, recycled plastic and wood particles. The wood supporting structure of the deck is retained.

Composites are widely sold at home centers and building-supply outlets, and some of them have built-in, permanent coloring. No finish is needed on these materials and they won't rot, split or splinter.

Even composites are not perfect, however. They still need periodic cleaning, and they can develop mildew.

Our brick fireplace is dirty. I tried cleaning it with soap and water, but that didn't help. What do you suggest? -- A. Bashaw

Many fireplace-equipment dealers sell special cleaners for fireplaces, and I suggest you try one of these first. Check under fireplaces in your yellow pages for a dealer. If you can't find a source, you can buy a stone and brick cleaner from Improvements (www.improvementscatalog.com or 800-642-2112; item 195171, about $10 per quart.).

Trisodium phosphate, a heavy-duty cleaner sold at many home centers and paint stores, can also be used to clean dirty fireplaces. Start with a solution of one tablespoon TSP in a gallon of warm water. Use a soft scrub brush and wear goggles and rubber gloves. If the bricks are still dirty after using this solution, double the amount of TSP and try again.

Questions and comments should be sent to Gene Austin, 1730 Blue Bell Pike, Blue Bell, Pa. 19422. Send e-mail to doit861@aol.com. Questions cannot be answered personally.