Q. Our home is just a slightly more than 15 years old. It is part of a major development where all the homes are of the same basic construction and age. Recently, several of our neighbors have invested in new roofing.

Although I have not had any serious problems with our asphalt shingle roof, it may be time to consider repair work or reroofing.

How long should the original roofing last and what should I look for in deterioration that would indicate a new roof is advisable? If we do need new shingles, can these be applied over the existing ones?

A. It is wise to inspect your roof at least twice a year. Problems identified and corrected early can ward off more serious repair work later.

Your inspection should start on the interior of the home. Look for signs of water damage.

Water from roof leaks can travel unseen along beams and rafters into the interior walls. Water damage may result on the ceiling, near the ceiling along walls or farther down and still be the result of roof leaks.

Inspect the attic, particularly after a hard rain. Use a flashlight to examine the roof sheathing and rafters for wet, darkened or stained wood, which indicate leaks.

On the exterior check the condition of your shingles. A pair of binoculars is helpful. Look for cracked, warped, frayed or missing shingles. Valleys of the roof, where two sloping sections meet, are particularly susceptible to damage and leaks because this is where the heaviest flow of water is carried. Inspect for signs of excessive wear.

Because of safety factors and potential damage to your roofing, it is best not to go onto the roof yourself. Footsteps on roofing shingles can damage their surface and if the roofing is weak it can give way.

If you suspect your roof needs repair or replacement, it is best to call a roofing contractor to make the inspection. Many contractors provide free inspection service.

If you do need a new roof, often a second roof can be installed over the original roofing. Usually a third installation is not recommended because of added weight.

Things to look for in a qualified contractor:

The contractor should be insured so you are not liable for any accident that could occur on your property during the job. The contractor should be bonded and licensed.

Check references from previous customers. You should find out all cost factors, including whether the contractor met the bid price or charged more for last-minute extras, and determine the efficiency of the work crew and how well the site was cleaned up after the job was finished. Most important, determine if the job was completed to the customer's satisfaction.

Get a written guarantee and go over everything concerning the job in writing before you agree to have the work done. It is usually best to get more than one bid.

Know what work will be performed, what materials will be used and how long the project will take. Get everything in writing. Don't sign any document until all specifications are written to your satisfaction. Keep copies of all paperwork.

Check the completed job, even if it means going up on the roof with your contractor.

Q. The grout between the tile in our bathrooms has become dingy and gray over the years. I have tried various cleaners, but they have not done a very good job. Do you have any suggestions?

A. To get rid of the soapy film that builds up on bathroom tile, wipe with a solution of one part vinegar and four parts water. Rinse thoroughly with clean water.

For more stubborn stains apply a solution of three-fourths cup household bleach mixed in a gallon of water. Apply with a sponge or brush with a toothbrush. Rinse thoroughly. Some commercial tile cleaners with bleach are K14 or Tilex.

Other methods of removing stains include rubbing the grout with a typewriter eraser, or even lightly sanding the surface of the grout to expose a fresh clean under layer.

If these methods are unsuccessful, try removing about a half inch of the surface layer of grout with a grout saw and re-grout over the older layer.

Send inquiries to Here's How, Copley News Service, P.O. Box 190, San Diego, Calif. 92112-0190. Only questions of general interest can be answered in the column.