Q: I have removed a door between two adjoining rooms and plan to remove the frame and replace it with an arched opening without a door. My problem is framing and finishing the arch. Is gypsum board flexible enough to be used for this?

A: It depends on how sharp a curve you are making. Thin gypsum board can be curved to moderately large radii, but if the curve is too sharp, or the board too thick, it will crack. However, you can often curve it without cracking by cutting a series of slits or cracks on the inner side. (These will have to be filled later.)

On arches around windows and doors another technique is to use thin plywood or hardboard instead of gypsum board. When this is sanded smooth and painted or papered over, it will look just like the rest of the wall. Either way, you will have to use tape along the edges, then apply joint cement over this.

Q: During the heating season I have a serious condensation problem on my upstairs casement windows. I have storm windows installed, but they don't seem to improve the situation. A friend suggested we replace the existing casement windows and storm windows with Thermopane double-glass windows to eliminate the problem. Do you think it is worth spending all that money on replacement windows?

A: I don't think it would be worth the expense if condensation is your main problem. Condensation is the result of the glass being much colder than the inside of the room, and your storm windows should have helped to some degree. Since they didn't, it may be that they do not fit properly. Or it may be that the relative humidity inside the house is too high -- it should be no more than about 30 percent to 35 percent when the temperature is near freezing outside.

Also, you may need more venting in the bathrooms and kitchen to let moist air escape. Try adding a third layer of glass or plastic on the inside by putting up a do-it-yourself plastic storm window unit on the inside of the window. The extra insulation should help considerably.

Q: The cast-iron radiators in our house were painted with flat latex paint. This winter the paint cracked and peeled and we want to redo them. What is the best way to get all the old paint off and what type of paint will adhere better to the radiators when they are hot?

A: Use semi-paste paint remover to get the old paint off, then rinse the metal clean and allow to dry thoroughly. Give the radiator a first cost of rust-inhibitive metal primer, allow to dry thoroughly, then paint with low luster or flat paint in the color of your choice. I think an alkyd will stand up to the heat better than a latex paint. c

Q: As the toilet tank in my bathroom fills after the bowl has been flushed, there is a bang when the water shuts off (after the tank is full). Is this due to the copper pipes being loose, or do you have any other ideas?

A: It could be that some of the pipes are loose, so check as many as you can see or any that are exposed in the basement under that room. The hammering noise is probably caused by a condition known as "water hammer." When the tank valve suddenly shuts the water off, the rushing water slams to a stop and starts the pipes vibrating -- and this causes the noise. You should be able to control it either by installing an antihammer device in the water line just below the toilet tank, or by replacing the ballcock with another that shuts off more smoothly. It could also be that both measures will be required.

Q: In the past six months the paint on my kitchen walls and ceiling has been splitting into vertical and horizontal cracks, much the way a grape skin splits. There is no flaking or peeling yet. This is an old apartment house and my kitchen was painted with semigloss latex paint about 18 months ago. Any suggestions as to what I can do before repainting?

A: From your description, it sounds as though you have a condition referred to in the trade as "alligatoring" (looks like an alligator's skin). This can be caused by applying one coat on top of another before the bottom coat has fully hardened, or by applying a finish coat of hard-drying paint on top of a soft-drying undercoat.

It can also be caused by applying paint over a very glossy surface, and sometimes it happens when paint is applied over a surface that is coated with a light film of wax or grease. In any case, if it is now thoroughly hard, and if it is not peeling or flaking, you can fill in all the cracks with spackling compound, or you can use a sander to smooth the surface by sanding away the top layer until the cracks are no longer visible.