When recaulking, tile and joints must be spotless

Q. We are faithful readers of your article in the Daily Herald; thank you for all of the help we have received.

This past spring, you had an article praising Sikaflex. Having caulked — and recaulked — with other products, we found the Sikaflex and applied as directed. As I hope you can see from the attached pictures, the caulk has separated from the wall/floor. Should we caulk over, or start over?

A. If the previous caulking material was silicone — which is most likely, as it is recommended by many people and widely available in hardware and paint stores — no other caulking, including more silicone, will stick for long.

All traces of previous caulking must be removed and the joint thoroughly cleaned. To do so, try WD-40 or DSR-5 (dsr5.com) and a putty knife, paper towels, clean rags — whichever works best.

Your photo shows a brownish stain that looks like mold at the floor/wall joint and in one joint higher up. This also will need to be removed. Try a Clorox bleach pen. When the stains are gone, wipe the treated areas with a damp cloth, followed by a dry one.

After that, Sikaflex-1a should adhere and last a long time.

Q. My home is a 70-year-old, well-built brick home that is well taken care of. I replaced the Carrier furnace two years ago with a high-efficiency Carrier furnace with a humidifier. Now in winter, all 15 windows have an excessive amount of moisture on the inside — not between the double panes, but on the inside.

I have been complaining to the installer, who has asked me, “Do you have plants?” No. “Do you do a lot of cooking?” No, I bake everything I cook. “Do you have pets?” No. The answer was “no” to all the questions asked. I am the only one who lives here.

The new furnace is vented to the outside, not like the old furnace, which was vented up the chimney. All the gauges that I have throughout the house read between 30 and 50 percent relative humidity, mostly 30.

This problem never occurred with the old Carrier furnace. Why is it happening with the new furnace?

The installer does not have a solution. Now winter is upon us, and when the temperature drops to 30 or below, all 15 windows sweat like a river. I am 79 years old, and I need a solution.

A. The old furnace, vented through the chimney, needed make up air for proper combustion. It got it through the many cracks around windows, doors and other building components, constantly changing the air in your house.

The new, more efficient furnace gets its needed make up air through a separate pipe next to the exhaust pipe or by means of a pipe within a pipe. As a result, the number of air exchanges in your house has been reduced considerably.

Thirty percent relative humidity (RH) is quite reasonable in the winter. Since you have none of the possible sources of moisture, that is not the problem, although you were not asked whether you dry clothes on racks indoors — a considerable source of moisture.

The problem may be due to your windows. Are they single-pane, which was common in houses built in the ’40s? Even if they are double-paned, you may need storm windows.

Q. Some time ago, a question in your column was about venting a dryer into the home for added warmth. Is this feasible? The dryer in my daughter’s townhouse must vent up more than 12 feet through an attic and out the roof. Lint can’t travel that far, falls down and accumulates at the back of her dryer.

Someone told her about a “lint box” that attaches to short tubing from the dryer and vents inside the laundry room. Is this possible? Have you ever heard of this?

A. Venting a dryer into the house is not recommended. It may create excessive moisture that can damage walls and paint and cause condensation on windows. This is particularly important in homes built or made more energy-efficient, because they have fewer air exchanges per hour and often suffer from levels of relative humidity that are too high.

Your daughter’s venting is a nightmare. Lint that accumulates in the vent is preventing proper drying of the dryer’s load; this can lead to condensation that can leak through joints in the venting system. It also can cause the dryer to overheat, which presents a serious fire risk.

If her dryer cannot be vented through an outside wall, she should seriously consider installing a booster fan on the section of venting in the attic. The Fantech model DBF110 is especially designed to be used with dryers and includes an automatic pressure switch that activates the unit whenever the dryer is running. A licensed electrician should install it.

She also may want to consider a dryer with a lint filter that is so efficient practically no lint passes by it. Since we switched to a Bosch dryer, we no longer have to clean the vent cap outside.

Q. We have a mold problem on the linoleum floor in our family room downstairs. What would you suggest we use? The room is not very well lit and has only a small window to let in air. We can’t afford to hire a professional. Can you advise as to how we can do this ourselves?

A. If it is surface mold, you should be able to remove it with an oxygen bleach (ecogeeks.com) or a mixture of one part fresh Clorox bleach to three parts water.

But if it is an internal stain caused by moisture that got into the back of the linoleum over time from a leak, or that rose from the concrete slab, it cannot be removed. In that case, replacing the linoleum without addressing the cause will result in a repeat of the problem.

Q. In a recent column, you provided the following formulas for getting rid of algae and moss on roofs: (a) For algae, use three parts fresh Clorox to one part water, and (b) for moss, use three parts white vinegar to one part water.

For moss, you said to spray the vinegar solution over all affected areas (best in warm weather) and do not rinse. You said time and weather would do the rest.

But you did not tell us how to use the Clorox solution on algae. Do we spray the solution on affected areas and then not rinse, as was done with the vinegar solution on moss? Your expertise would be much appreciated.

A. You can try spraying the roof with a solution made of equal parts fresh Clorox bleach and water. (The original formula you cite was given to me years ago by a scientist from the Texas Forest Service, who has since told me that equal parts Clorox bleach and water work as well.) One gallon of the solution will treat 50 square feet of roof. Spray it from a ladder on a windless day, and do not use so much solution as to cause a substantial runoff.

You also can use an oxygen bleach such as OXY-Boost (ecogeeks.com); follow package directions carefully.

If you have metal gutters, run water from a garden hose through them during the spraying. Before starting to spray, thoroughly wet all vegetation below the roof and then cover it with plastic. Soak the vegetation again when done spraying the roof.

I hope this helps.

Q. Our two-story house is about 10 years old. It has a fan that opens to the cedar roof. The fan is connected to a thermostat and a humidistat. It runs a lot, keeping the attic cool and dry.

We have noticed that it is screened only with chicken wire, so sometimes bees get into the attic during the summer. Our exterminator would like us to replace the chicken wire with a smaller-mesh screen, but our HVAC contractor says that type of screening collects too many leaves and other debris that must be cleaned regularly. What would you recommend?

A. I wish you had mentioned the make of your fan. Without this information, I can’t tell where the chicken wire screening is. Chicken wire sounds rather unusual; I am more familiar with the use of hardware cloth.

Since your HVAC contractor is concerned about the restriction that fly screen would cause, you could build a large framework with 2-by-2-inch lumber in the attic below the fan and staple fly screening on all sides and bottom. Insects would still be able to get past the fan but not into the attic.

You haven’t said where you live, which would affect my feeling about the use of your roof fan. You may have read before that I am not a fan of roof fans. They can be helpful in hot climates, but only if there is enough net free ventilation area (NFVA) to satisfy the CFM rating of the fan. Otherwise, the fan robs conditioned air from rooms below the attic, causing an increased use of energy. A light-colored roof is a better way to keep an attic cooler in the summer.

In colder climates, an attic fan operating in the winter can rob heated air from the living quarters. It is best in all cases to vent attics with a combination of soffit and ridge venting.

Q. We have outdoor carpet on a back porch and steps that is growing green moss. What can we use to rid the carpet of moss and keep it from growing back? Bleach is out of the question.

A. Try an oxygen bleach. The one I use is OXY-Boost (ecogeeks.com, click on “OXY Products”). Exterior PROx Nontoxic Deck & Patio Cleaner (click on “Outdoor”) is also a good product to use, but its effects, for some unknown reason, are not as long-lasting as OXY-Boost’s.

But I know of no product that will assure you that the green moss won’t return.

Q. Please advise: Is it too late to roof a small ranch house this time of year? Would a sunny November day be warm enough to seal the shingles for a good fit?

A. It is taking a chance, but some people go ahead and do it. The sun is not strong enough in mid- to late November, and it shines — when it does — for too few hours to seal the tabs properly. On the other hand, you might be OK — if no strong wind blows off some shingles — because snow will soon cover the roof.

My preference would be, unless you have an emergency, to wait until the warm weather returns.

Feedback from readers: Following my suggestion to get rid of fruit flies by placing a slice of overripe banana in a glass jar, covering it with plastic wrap and punching a few holes in the top (the flies get in, but can’t get out), a good friend told me that she had heard that vinegar is also an effective bait. I asked anyone who had tried it to let me know their results.

Two Vermont readers reported that they used apple cider vinegar (one also added a drop of dishwasher liquid) and that it worked beautifully. The advantage of the vinegar over the banana is that the flies drown, so disposing of them is quite easy — down the drain.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Email him at henridemarne@gmavt.net.

© 2012, United Feature Syndicate Inc.