Corroding chimney needs care

Q. We rent a 100-plus-year-old house from my mother-in-law. The house was originally heated with coal. A gas-fired hot water heating system was installed in the '60s. The brick chimney is corroding in spots, and the bricks are turning to dust, but the mortar is holding fine. In the attic, a brick has completely dissolved and a hole can be seen into the chimney. What can be done about this? Can a gas furnace be vented outside without a chimney?

Also, the kitchen floor has carpet over tile. The tile is breaking down in spots and, where we can pull the carpet back, we can see white fibers in the floor tile. Could this be asbestos or some other material? The tile was installed in the '50s. If it is asbestos, is covering it with carpet safe?

A. Your chimney situation should be taken care of immediately; there is a risk of fire, carbon monoxide leakage (I hope you have carbon monoxide detectors on each level of the house), and even collapse of the chimney.

Most modern boilers and furnaces are vented through a wall nowadays, but this would not be the case with a boiler installed in the '60s. It may be time for you to replace the boiler with one that is far more energy efficient, and that can be vented through the wall.

In any case, the chimney needs to be checked over by a certified chimney sweep or masonry contractor to determine whether it is structurally safe and, if not, whether it can be repaired, rebuilt or should be taken down.

If you do not plan on replacing the boiler, the chimney still needs to be evaluated for structural integrity. If it is found to be repairable, it should be fixed and then lined with a stainless steel or injected-concrete liner.

The disintegration of the old bricks (which are not hard-burned, as modern bricks are) is most likely due to corrosion from the combustion gases of coal burning; I am surprised that the installers of the gas-fired boiler did not suggest lining the chimney at the time of the conversion.

The combustion gases from a gas-fired heating system can cause oil or coal deposits on the chimney walls to become even more corrosive, which is why a chimney should be cleaned and inspected at the time of conversion. An old and most likely unlined chimney should not have been used without a new lining.

Regarding the kitchen floor tiles, the fibers you see may be asbestos given the tiles' age, but the only way to make sure is to have these fibers analyzed by an environmental testing laboratory. If they are found to be asbestos, the tiles should be removed by specialists trained in this work and in proper disposal.

An alternative would be to cover the tiles with an underlayment and carpet or tile over it, but this may affect built-in appliances, such as a dishwasher, which would not be able to be removed without complication when it needs to be replaced.

Such appliances would be locked in by the newly raised floor, and removing them would require removing the countertops that cover them.

Q. What can I use to keep snakes away from the house? It used to be farmland with a house and outbuildings.

A. I know that, to many people, snakes evoke revulsion, but they are very useful predators of mice and other rodents, as well as other nuisance creatures of the wild. If snakes are around your house, it must mean that they have a good food supply. Keep in mind that they are as afraid of you as you are of them - perhaps even more so.

One way to keep them some distance from your house, although it is not very practical, is to spread wood ashes or lime around the foundation. This can get pretty sloppy if it gets wet and tracked into the house, and you would have to reapply it after every rainfall.

Q. Our ranch house sits on a very wooded lot, so we always have lots of leaves and other debris from trees in our gutters. We have overhangs on various sides of the house that range from 2 feet to 5 feet.

We have had problems with the 5-foot overhang - gutters icing up in winter, deteriorating the seams on the plasterboard of the underside. We installed roof-heating cables (including in the gutter) that have helped some. The cables are clipped on only the lower 2 feet of the overhang. There is a roof vent and vents at the edge of the overhang.

We are now contemplating installing the Gutter Helmet. It has been suggested that we remove the heating cables. What are your thoughts? If we retain the heating cables, should they be extended to the entire width (5 feet) of the overhang? - Pittsburgh, Pennsylvania, via email

A. Neither the Gutter Helmet nor any similar product would solve your problem. Ice dams form because snow melting from an attic temperature above the freezing point runs down the roof under the snow cover and freezes as soon as it gets onto cold eaves. Electric roof cables can help, but have some drawbacks as well. They are expensive to run, they can short-circuit and, in very cold weather, icy V's form and trap water. I have also seen cables ripped off roofs by huge amounts of ice. Although the Gutter Helmet and similar products are advertised as eliminating the need for gutter cleaning - a definite plus - I do not see how they can allow the gutters to function as they are designed to in hard rains. These products work on the principle that the surface tension of water causes the rain to follow their contours. That may work in gentle rains, but in heavy rains I believe water will simply jump past the little opening they provide for water to enter.

If your yard can take the spillover from such downpours, it may be worthwhile using one of these products to keep your gutters cleaner than they are now. However, I don't know how they can prevent pine needles and other small items, like spring blooms and tree seeds, from getting into the gutters. And how do you clean the gutters once the helmet is installed?

The best way to stop ice dam formation is to have a cold roof - that is, heavy levels of insulation and plenty of ventilation. From your description it sounds as if you lack one or perhaps both, unless by "a roof vent and vents at the edge of the overhang" you mean full-length ridge and soffit vents.

If your roof is near the end of its useful life, you should seriously consider having a special membrane such as Grace Ice & Water Shield installed under the shingles for as high up the roof as is recommended for its pitch and the width of its overhangs.

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. His book, "About the House," is available at www.upperaccess.com. His website is www.henridemarne.com. Email questions to henridemarne@gmavt.net, or mail First Aid for the Ailing House, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.

© 2015, United Feature Syndicate Inc.