Do-It-Yourself

Q: I have heard that mold can grow behind a bathtub liner. Is this possible? -- Anna

A: Yes, if water gets trapped between the tub liner and the original tub surface. Water can enter any joint that is not thoroughly sealed. With a typical tub liner, which is a tough plastic shell molded to fit into the existing tub, leaks are possible at the rim joint of the tub and liner, the drain, and the overflow opening. A "squishy" reaction when someone stands in a tub is said to be a symptom of water under the liner.

Hundreds of thousands of tub liners have been installed in homes, hotels and other buildings since about 1980, when they became popular. To the best of my knowledge, liners are considered excellent treatments for beat-up tubs. The best protection against leaks is to choose an experienced installer and a top-quality product. Ask the installer if he is willing to give a written warranty against leaks.

There is a great deal of information about mold and tub liners on the Internet, but much of it is sponsored by the tub-refinishing (painting) industry, which competes with the tub-liner industry. You can find this information by using a search engine and terms such as "mold" and "bathtub liners."

Q: Why do my furnace ducts make a banging noise when the heat goes off? -- J. Donnellan

A: Metal heating ducts can make banging noises for a couple of reasons. For one thing, metal expands when it is heated and contracts when it cools, which can cause noise in loose ducts. The force of air pushed through the ducts by the blower can also cause movement and noise if the ducts are not tightly assembled and supported.

Duct noise can sometimes be reduced by taping joints and making sure ducts are well-supported with straps.

Q: Is it possible to paint a concrete deck so the paint will last? -- L. Jackson

A: It is definitely possible, but the results hinge on the same factors that affect other paint projects. Choose the correct paint and carefully follow directions for preparing the surface. Use paint specifically designed for concrete floors; several varieties, including epoxies and water-based paints, are available at paint stores and home centers. Epoxies are the toughest and longest-wearing but are somewhat more difficult to apply. Preparation will include repairing blemishes such as cracks, cleaning thoroughly, possibly pressure washing, and perhaps etching the surface with a chemical etcher to improve adhesion.

Concrete also can be stained, incidentally. This is a good option if the surface is in good condition because stain penetrates and is much less likely to peel.

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.