Q: A flat roof on our house has a sag or dip in one corner so that puddles remain there after every rain. Evidently when the roof was put on (about 10 years ago), it was not pitched properly. There is no leakage into the house and a roofer told us that as long as there is no leak, we should leave the roof alone. Do you agree that we should do nothing at this time?

A: Yes, I agree with the roofer. Water lying on the roof will do no harm so long as the roof covering is solid and not leaking -- so don't worry about it.

Q: I recently purchased a contemporary home that has exterior siding of unpainted pine. I planned to apply a wood preservative to this pine, but the previous owner said this is unnecessary -- in fact, the wood would last longer if left alone. What is your opinion?

A: Any wood will last quite a while even if untreated, but it definitely will last longer and stay nice looking longer if protected with wood preservative or paint. A preservative will also help protect against cracking and checking.

Q: I have a cement-block house and am having a problem with mold and dampness on the lower part of a closet on an outside wall. I have checked for leaks around the outside, but find none. Could condensation be forming on the inside because it is colder on the outside and, if so, would insulation solve the problem?

A: Because it is an outside wall, and because closet doors are closed most of the time so warmth from inside the room cannot penetrate, condensation is probably causing your problem. I think putting a louvered door on that closet would help (try leaving the door open for a few days as a test). Insulation also would help, but it should have a vapor barrier on the inside (on the warm side). If you use sheets of plastic foam as insulation, they must be covered with gypsum board because the foam is inflammable.

Q: Like many other houses in my area, the kitchen has incandescent lights recessed into the ceiling. Above is an unheated attic that goes out over an unheated garage. We have insulated the floor of this attic, but cannot cover the light fixtures due to fire hazard. As a result, cold air keeps spilling down from each fixture. What can we do to correct this?

A: First check around each fixture. Openings or cracks around each one are probably allowing cold air in. If so, you can caulk or stuff insulation around each one. Also, you can build a box over each fixture large enough to prevent heat buildup. The box should be at least twice the size of the fixture, and about 10 inches high. In addition, place some slots or louvers in the sides to help dissipate the heat.