QMy house was built in 1951. The electrical wiring is armored cable, some of which runs under the fiberglass insulation in the attic. The insulation around the wires is cloth and it appears to be fraying and crumbling at the outlets. Do I need to have my house rewired or at least have the wiring inspected for safety? -- S. Wall

AMany older houses would benefit from a thorough wiring inspection by a qualified electrician. Use of electricity in homes has vastly increased in the last 50 years, and many old wiring systems are not up to the load placed on them.

Some modern electrical safety devices, such as ground-fault circuit interrupters, which can prevent shocks and other problems by instantly switching off the current if a short circuit is detected, are required in new homes but do not exist in most old homes. Metal-clad cables have also largely given way to wiring clad in tough plastic.

Another problem in some older homes is that along the years do-it-yourself electricians have installed wiring that is not up to electrical codes or safety standards. Also, thousands of homes built from 1965 to 1973 might contain aluminum wiring, which can create a fire hazard by overheating outlets and switches.

My townhouse has concrete exterior window sills that are cracked, chipped and dirty. Can I resurface these sills without removing them? -- N. Glassman

You can patch up the cracks and chips with vinyl patching cement, sold at most home centers. This product can be spread in very thin layers and has good adhesion to old concrete. However, the cracks, which are probably from a slight settling of the house, will probably reappear in time, or new ones will appear.

You might also be able to use an excellent covering method used by many replacement-window installers on wood sills, which are notorious for peeling paint and cracks. The sills are covered with a thin skin of pre-finished aluminum. With concrete sills, the skin could be fastened in place with construction adhesive such as Liquid Nails. This is usually a job for a window contractor, because special tools are needed to shape the covers.

My granite countertop has stains from dish detergent. Can you help? -- F. Tufaro

These expensive countertops should be protected periodically with a sealer, which can help prevent stains. Special cleaners and sealers for natural-stone counter tops are available. You might be able to find appropriate products at a nearby home center, or you can select from a wide array of products at the Web site store.graniteearth.com/care.html. These products include a soap-scum cleaner (about $15) and kits containing cleaner, sealer and polish (about $75). Even with a sealer, you should try to avoid spills and drips on the counter.

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.