QOur blacktop driveway has deep cracks that I have filled many times. The patches don't hold up. I can't afford to tear up the old driveway and put in a new one. Do you have any suggestions for making patches that will last?

-- A. Jones

AIf these cracks are more than about 1/2-inch wide, use cold-patch blacktop mix, which is sold in bags at home centers and hardware stores. Cold patch contains an asphalt binder plus some aggregate (usually sand and small bits of gravel). Follow the directions on the bag for applying the cold patch, but generally, the crack must be cleaned, then the patch is poured or troweled in (best done on a warm day) and then the patch is tamped down firmly. A metal tamper is best, but you can also use a length of 2-by-4-inch or 4-by-4-inch wood.

If there are a number of cracks in one area, it is best to dig out the deteriorated surface and apply cold patch over the entire area. A layer of gravel under the cold patch is sometimes recommended, but many experts say a "full-depth" patch is best. That means using cold patch right down to the original base of the driveway.

Smaller cracks in blacktop can be trickier to patch. I have tested many types of patching materials for small cracks over the years. I got much the same results that you got. Most patches last for a year or less before shrinking or deteriorating and allowing the crack to open again. Patching compounds for smaller cracks come in several forms: caulking cartridges, jugs, cans and plastic tubs. I got the best results with a silicone-based caulking-gun compound that cost about $3 for a 10-ounce tube.

Unless a driveway is in extremely poor condition, it is often not necessary to tear it up to install a new surface. A new layer of blacktop can be laid right over the old.

We are trying to improve the energy-efficiency of our older brick house and have already completed a number of energy-saving projects, such as insulating the attic and replacing the windows. Would painting the outside of the house for insulating purposes be a foolish move? -- M. Files

Painting the outside of a brick house for insulating purposes is definitely not something I would do. So-called insulating paint, which is basically a reflector, might cut your summer cooling bills a bit by reflecting some of the sun's heat away from the house, but I seriously doubt that the difference would be worth the expense.

In addition, painting the bricks could cause maintenance problems (peeling and chalking paint, for example) that could bother you for many years. If there is no other practical and cost-efficient way to insulate the walls, my advice is to leave them alone.

The wrought-iron railings outside our house are painted black, but the paint is chipping in spots and some rust is forming. How do we prepare the railings for re-painting, and what type of paint should we use? -- Gary

Start by removing all the loose paint by scraping or sanding. Wipe the railings to make sure they are clean and free of dirt and dust. Coat the rusted and bare spots with Rust-Oleum's Rusty Metal Primer, which is sold at home centers and paint stores. When the primer is dry, apply a coat of rust-resistant exterior enamel. Wrought-iron railings are often painted black, so you might want to stick with that color.

We have a brick walkway set in mortar. It gets a greenish coating that came back even though we pressure-washed it. Also, some of the mortar appears loose and cracked. Any suggestions?

-- B. Smith

If you own a pressure washer, it is probably the best tool for cleaning the walkway. You will need to clean periodically because the conditions that caused the greenish tint (mold) will probably still exist. These conditions usually include moisture and shade. Scrubbing with a chlorine-bleach solution (a cup or two of bleach to a gallon of water) should also eliminate the mold, but it is likely to return after a while.

Loose mortar should be cleaned out and replaced with fresh mortar, which is sold in bags at home centers and hardware stores. An old screwdriver makes a good tool for digging out the mortar, and a small trowel can be used to make the repairs.

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.