Home repair: Saving time on pre-cutting Sheetrock

Q. To save money, I plan on doing the interior finish of our new addition myself. I think I have the skill to do most of the finish, but I am not sure how to handle cutting the openings in the Sheetrock for all the electrical boxes, especially those in the ceiling for the light fixtures. Do I measure from several sides and cut out the hole with a utility knife? What if I am slightly off and have to take the Sheetrock down from the ceiling to cut the holes again?

A. What you describe is the way we used to do it, but with the advent of new tools, that is no longer necessary. Construction workers now use Rotozip tools to cut the holes for the boxes after the fact. Not only is this much easier; it's also much more accurate.

Install the drywall without any cuts for electrical boxes. Once it is on, feel with your hand for the hump, the half-inch protrusion that the boxes create. Drill a hole with the Rotozip tool somewhere in the hump, and zip to the side of the box. Once there, jump over the side of the box, drill a hole on the outside next to the box, and follow the box contours. Press the gyp board around the box so its outside sits flush with the box.

You can buy one of several versions of the Rotozip tools in building-supply and hardware stores. Bosch makes Rotozip and Dremel tools. Good luck with the job.

Q. My house is just 8 years old, and I have condensation on my windowsills in the master bath and master bedroom. These rooms are on the north and northeast sides of the house. The moldy mildew is black with a fuzzy coating, and it is embedded into the wood, which has lost its stain and varnish or urethane coating. I have tried to remove it with a mixture of bleach and water, scrubbing it with a toothbrush, but the black mildew has pitted into the wood too far. Aside from new windows, what can I do?

A. The relative humidity (RH) in these two rooms is too high. Do you keep the temperature lower or the doors shut? North and northeast rooms are more prone to condensation problems because of their exposure, so you may need to increase the temperature in them. Keeping doors open and using a bathroom fan while showering should also help. If this does not do it and you have hot-water baseboards, you may need to have radiation added. If you have warm-air heat, make sure that the register flaps are fully open. If they are, the system may need to be balanced. Hopefully, the builder used energy-efficient windows in an 8-year-old house, but if not, rather than replace them, consider adding storm windows.

To remove the deeply ingrained black mold, try using full-strength Clorox bleach. If that does not do it, try using a saturated solution of oxalic acid. Buy the crystals in a paint store (much less expensive than in a drugstore) — you won't need much — and mix them in hot water until some of the crystals can no longer be absorbed. Apply the solution with a small brush, and let it do its work. When you are satisfied with the results, wipe off the residue with a clean cloth dampened in white vinegar. Oxalic acid is potent; wear rubber gloves and skin and eye protection, and use care not to spill onto any other areas. Restain and/or revarnish the wood.

Q. My home was built in early 1920s, and my problem is dust! I literally dust every day, and the next day it is back. It is not a light covering; it's major dust. I also vacuum almost daily. Why do I have so much dust?

My home has a cinder-block foundation with a concrete floor in the basement. There is some exposed insulation in the rafters, but only near walls, not all over the basement. We replaced an octopus heating system when we purchased the house, and replaced most of the ductwork in the basement, but not on the first floor. Our basement walls are plaster, as are the exterior walls of the basement; the rest of the home is vinyl siding. The original walls on the first floor are plaster. A second story was added in 1985 with drywall, and a first-floor family room was added in 1987.

Is there anything I can do to help with this problem? I spend way too much time dusting and vacuuming.

A. The first thing to do is to have the ducts professionally cleaned. Look in your Yellow Pages for such a listing. There may be a considerable amount of dust that has accumulated over the years in the ducts you haven't replaced. You should also check the furnace's filters often and replace as needed until the problem is cleared up. Or you may decide to have an electronic filter installed. Although they are quite expensive, they are supposed to remove 90-plus percent of the particles flowing through them.

If the windows in your house have not been changed, they are probably major sources of infiltration of external dust. This may be especially so if you live in an area with industrial pollution, such as coal plants, or with farmland soil stirred up by wind. The basement insulation may also be laden with decades of dust; replacing it may help.

Old plaster walls may need to be thoroughly cleaned. Also, what is behind the vinyl siding? When it was installed over what is probably plank sheathing, was a housewrap applied as an air barrier? This would stop infiltration that can enter the house through various cracks and spaces around electrical and other openings.

Q. What product can I use to clean older kitchen cabinets. The cabinets are functional but have stains from cooking, water, etc. They are dark brown in color.

A. Try Milsek Furniture Polish. Many readers have told me how fabulous it is at cleaning and restoring dingy, greasy, aged furniture of all types. You can buy it at www.milsek.com.

Q. About six months ago, I cleaned a bare concrete block wall in my basement with etching compound before applying Drylok masonry waterproofing paint. An area underneath the chimney cleanout had some heavy stains from creosote. I thought the etching solution would clean the creosote off well enough to enable the paint to stick. I was wrong, and the paint is blistering off where the creosote is. How can I remove the creosote from the blocks so the masonry paint will stick?

A. Unfortunately, I know of no way to remove the creosote stains deeply embedded into the porous masonry. You may want to try coating the stained area with B-I-N and see if it will stick to the concrete blocks. If it does over time, apply Drylok over it.

Q. We have two problems. First, mold on the shingles. I need a confirmation that Stainhandler is what we need. This is a mystery to so many people. I would like to get the shingles brought back to life in the spring. I've read that the product should be applied before your shrubs come in.

Our other problem is one front bedroom that is cold in the winter. Could be the furnace; however, I did see foam advertised that can be applied from the outside through the mortar. This procedure sounds good, but buyer beware, right? Can you help in any way?

A. Stainhandler Roof Deck Cleaner should get rid of the algae that cause the discolored areas you see on so many roofs. Just be sure to follow the manufacturer's instructions. The suggested concentration of the powder with water may need to be increased to take care of darker stains. In normal concentrations, Stainhandler should not harm your plantings, but follow the recommendations to wet them before the application of the solution and rinse them afterward. Covering them with plastic is also advisable. Once the roof is cleaned, consider having Stainhandler Zinc Strips installed just below the roof ridge to keep the algae from returning.