Siding stain most likely fungus, not mold

Q. Our daughter has a brand new home with vinyl-siding exterior. There are little dark dots all over the siding, which she thinks is mold. She had the same problem on her last house, also. Trees are not right next to or over the house but are on her property. Mulched garden plants have airspace next to the foundation.

Is this mold, and what can be done other than to wash the house every year? It is a big two-story house. If it needs washing, what is the best way? We have aluminum siding and never had this problem.

Linden, N.J.

A. The little black dots are most likely artillery fungus, as mold would be more like large gray stains. Artillery fungus is caused by the decaying vegetable matter in organic mulch. It's a spring and fall problem, as it is too hot in the summer and too cold in the winter. When ripe, the fungus explodes with great force and can jump 20 or more feet in height and is attracted to light colors. Unfortunately, it cannot be removed from vinyl siding without causing damage.

The solution to preventing further occurrence is to add new mulch over the old every year or to remove the mulch and replace it with rubber mulch. Rubber mulch is getting to be widely available in garden supply stores; it does not decay or support nefarious insect life, and it is quite attractive.

Q. I hope you can direct me. The hardwood floors in my home (circa 1950) have been described as "cupping." I had the floors refinished when I moved in (April 2006), and did not notice this condition at that time. My floor refinisher said I should increase the humidity control on my furnace (oil/hot air), but there is no humidity control. The house does not have a basement, and the furnace is in the crawl space. Suggestions?

Via e-mail

A. If the floorboards are concave, they are suffering from too much humidity from the crawl space. Is the crawl-space dirt fully covered with plastic? If not, this may be the cause of the cupping.

The solution is to reduce the humidity in the crawl space by covering the soil entirely with 6-mil plastic and closing any open vents. (Close them permanently; they are not needed in a crawl space in which the soil is covered.) You may have to put a dehumidifier in the crawl space for a while to dry it up.

If the floorboards are cupping in a convex fashion (far less likely), it probably means that the furnace is drying the air in the crawl space and causing the underside of the boards to shrink. But this should only be a seasonal problem that develops during the heating season, and the cupping should diminish or disappear during the summer. Increasing the relative humidity in the crawl space during the winter may help, but doing so safely is of concern. You do not want to overdo it to the point at which other problems develop -- such as mold on the joists and subfloor. It will have to be done carefully and be checked frequently. You may want to set up a hygrometer, which will tell you what the relative humidity is. It should not exceed 30 percent.

Q. I have a problem that no one seems able to fix. My house is an owner-built post-and-beam construction built in 1973. The main roof (about 500 square feet) has periodically leaked in one spot ever since I bought it in 1988. It happens only when there is a shift in temperature, usually when we have the first snow. The general consensus is that it isn't a leak, but condensation forms when the outside air changes, and it's the condensation dripping down, not water from outside.

It appears that the moisture has attracted some insects or ants to this one area. I can't see them, but I did hear activity last year when it was so wet. The two solutions suggested are:

• Raise the roof (which would have to go on top of what's already there because the roof is all one piece with no air space) and put more insulation between the interior boards and the exterior air.

• Insulate inside, which would have to go against the pine boards that serve as the ceiling.

If we did this, and it still created condensation, the trapped moisture would rot the wood. Right now, I have plastic suspended from the ceiling, creating a chute for the moisture to travel down so it doesn't get the bedding wet. It probably totals fewer than 3 cups a season, but it's not something I think I should ignore. I live on a fixed income and need to be careful about cost.

Westford, Vt.

A. Unless a very effective vapor retarder was installed prior to the application of the ceiling boards, it does sound as if you have a condensation problem, which is common with board ceilings.

But the question is: Why does it drip in only one spot? I assume that when you say that the roof is in one piece, it means that it is made of insulated panels with pine boards as ceiling and particleboard on to which the roofing is attached. If this is the case, it would explain why the leakage is occurring in only one spot. There may be a space between two adjacent panels that lets warm, moist inside air come into contact with the underside of the roofing. Shrinkage of insulated panels is quite common, and the solution is to determine whether this is the case, and inject closed-cell polyurethane foam in the space between them.

Yes, you probably have carpenter ants nesting in there. They like to do so in moist environments and foam. You should have a local, independent pest-management professional examine the roof and perform a treatment. I have seen one such specialist apply a gel near the affected areas that gets rid of the ants very quickly. Without more information, I can't recommend either of the fixes mentioned to you.

Q. My basement has a trench drain around the perimeter and a sump pump. My basement floods only under the following condition: The ground outside is frozen and there is a heavy, steady rain. I have not been home when the flooding has occurred, so I have no idea where the water is coming in. Do you have any suggestions?

Via e-mail

A. It sounds as if you have a grade problem. When the ground is frozen and it rains, water runs toward the house, since it cannot be absorbed by the soil. Look for low or flat spots, and add soil to raise them so the grade slopes away from the foundation. I assume that the trench drain collects the water and leads it to the sump pump, in which case the problem is minimal.

Q. We have a brick fireplace -- from floor to ceiling -- that was painted with oil paint many years ago, and latex two years ago. The reason we painted over the oil paint was because it was irremovable short of blasting -- even a grinder with wire wheel was ineffective. I would like to tile over the brick but am concerned about the attachment of the tile.

Should I use HardiBacker board screwed to the brick before tiling, or is there a product -- like a thin set -- that will allow me to attach the tiles directly to the brick? Since this fireplace is in the living room, I have eliminated the idea of using paint remover to get rid of the paint.

Via e-mail

A. There are paint removers that can be used indoors with good ventilation, but the clean-up of the residue is messy and may best be removed with a garden hose -- not the most practical thing in a living room. Your best bet is to use a tile backerboard, as you suggest.

© 2007, United Feature Syndicate, Inc.