Q: This summer I want to install a wood stove to save money in heating my home. I've heard that a concrete-block chimney is the cheapest and simplest type to build. What's involved in building such a chimney? Could a reasonably good handyman do the job? A: Building a concrete chimney using special ring-type blocks is deceptively simple: There's a lot more to it than simple stacking flue tiles and then slipping the ring blocks over the tiles.

First, you will need to build a good, solid foundation, independent of your house foundation and extending down below the frostline.

Next, you will need to rent scaffolding to stand on while you do the work. Setting this up is a two-person job. So is handling the concrete rings blocks -- they weigh about 50 pounds each, but seem much heavier when you're working 20 feet up in the air.

If will help to have a third person helping as well, mixing the mortar and feeding the two people up on the scaffold a steady stream of tiles, mortar and blocks.

In addition to a pair of helpers, you will also need some knowledge about how to build a chimney. You should know how to install a cast-iron cleanout door near the base of the chimney. And you must use the right materials. For example, refractory mortar goes in the joints between flue tiles, ordinary mortar is good for laying the blocks.

Considering the importance of owning a safe chimney, I'd say you should either hire a competent professional to do the job, or use a factory-made metal chimney designed for use with solid fuels. Q: We are going to paint the inside of our home and want to know how we can repair a hole in Sheetrock to make it smooth. A: To patch that hole in the wall, the first step is to use a keyhole saw to cut the hole roughly to a square shape. Bevel two opposite edges of the hole, and undercut the other two edges. Doing this will help lock the patch into the wall.

Next, cut a piece of Sheetrck about an inch bigger than the hole. Punch two holes through it near the center, and tie a loose loop of twine through these holes. Run a bead of glue around one face of this piece of Sheetrock right near its perimeter. Slip a scrap of wood through the loop of twine.

Then slip the Sheetrock through the hole in the wall, holding onto the stick and loop of twine. Twist the stick around and around until the twine is pulled tight like a tourniquet. This will hold the Sheetrock firmly against the back surface of the wall while the glue dries.

After the glue dries, cut the string and remove both it and the stick. Mis up a batch of plaster of Paris, and trowel it evenly into the area being patched. Do not use wallboard compound -- it will take days to dry and will shrink and crack in the process.

The plaster should set up in 30 minutes or so. Sand it smooth with 120-grit paper wrapped around a sanding block. If the patch is smooth enough to suit you, the job is done. If not, trowel on a thin coat of plaster, let it set up and sand again. Keep it up until you're satisfied. Q: Water condensation in the bathroom and around our metal-frame windows is causing paint to chip and peel off. And the window sills have gotten a dirty black stain from ice melting. What can we do? A: The best solution in the bathroom is a ventilating fan. These come in various capacities, measured in cubic feet of air moved per minute. To find the right size for your bathroom, multiply the length of the room times the width, times 1.1 (assuming the typical eight-foot-ceiling).

As for your metal windows, these are going to be a problem. If you don't have storm windows, installing them should help. Even the inexpensive indoor-mounted type should stop the condensation. The problem is that the metal frames are cold, causing moisture from warm room air to condense. The moisture then forms a breeding ground for mildew (that black stain you mention). Unless you can either warm the metal (by installing outdoor storms) or keep warm inside air away from the metal (by installing indoor storms) the problems will not go away. Q: Out walls are presently painted bright but dark colors, and we would like to go back to white and tan. What do we do other than priming them first to make sure that the dark colors don't show through? A: There's no need to use a primer when putting light over dark. Just amke sure the old walls are clean. Scrub them with a detergent before painting, and then start in with the wall paint of your choice. If you buy a quality paint, and apply it as thickly as possible, you may even get by with one coat. If not, just roll on another.

But don't roll the paint too thin. In my experience, most people do just that. Try to follow the spread rates recommended on the paint can label. Q: I've heard that there's some kind of flare that can be thrown into a wood stove to put out a chimney fire. I can't find any for sale in my area. Where can I buy one? A: A. chimney-fire flame produces great quantities of smoke that can deprive a chimney fire of the oxygen it needs to keep burning. I can buy them just up the road from my house at the local home center. If you can't find any in your area, write the manufacturer. What you want it the Chimfex Flare, made by Standard Railway Fuse Corp., Signal Flare Devision, Box 178, Boonton, New Jersey 07005.