An easy way to seal the base of the furnace

Q. I've owned my home for more than 20 years, and in all that time the forced air furnace has worked just fine. Now that I'm selling the house, the buyers' home inspector comes up with some nonsense about sealing the base of the furnace to the wooden platform inside the hall closet. He explained some mumbo jumbo about circulating air, or something like that. Would you please explain to me what he's talking about?

A. Don't get overheated about the furnace issue. The home inspector has pointed out a common safety issue, one that is often cited by gas utility companies. It should not be regarded as "nonsense" because it involves potential contamination of your home with carbon monoxide. Fortunately, there is a simple and inexpensive solution, as advised by the home inspector. Here is a basic explanation:

The bottom portion of your furnace, known as the return air plenum, is where the air from your home is drawn into the furnace to be heated and then blown back into the rooms where you live. The blower inside the plenum performs this function by creating a vacuum. If the base of the furnace is not sealed to the platform inside the closet, this vacuum can pull exhaust gases from the furnace into the circulating air stream. These gases would then be blown into your home, to the obvious detriment of you and your family.

The home inspector's advice therefore deserves your attention. All that's needed is to caulk the perimeter of the heater base to the wooden platform. When completed, you can call your gas company or the home inspector for a final inspection.

Q. Now that we're selling our house, the buyer's home inspector has faulted our garage roof for lack of drainage. What we have is a flat roof, and the framing has sagged, allowing rain water to pond at the center, rather than draining toward the roof edges. Fortunately, new roofing was installed less than one year ago, and no leakage occurred during the last rains. Still, the home inspector regards the lack of drainage as a substandard condition. Is it possible that this building, which was built in 1979, predates the current requirement for roof drainage?

A. A home constructed in 1979 would be subject to the 1976 Uniform Building Code. According to that code, "Unless roofs are sloped to drain over roof edges or are designed to support accumulated water, roof drains shall be installed at each low point of the roof."

Lack of adequate drainage is a common problem with flat roofs, and standing water on a flat roof increases the likelihood of leakage as a roof becomes older. Since the roof framing on your garage has sagged, it was apparently not designed to support the weight of accumulated water, and continued ponding is likely to cause further sagging of the structure. Therefore, the addition of drains at the low points of the roof would appear to be required and advisable.

• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

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