Here's How by Pat Logan

Dear Pat: I live in an old house, which seems to always have a moldy odor. Various sections are built over a dirt crawl space, slab and basement. Where is this odor coming from and how do I eliminate it? — Sheri J.

Dear Sheri: A moldy odor is generally caused by persistent dampness somewhere in your home. This is not only annoying, but it can be unhealthy for your children. Another potential problem from dampness is decay of the structural lumber supporting the house and how it attracts carpenter ants and termites.

There are two sources of dampness in a home. It can be generated internally from bathing and cooking and even from a humidifier set at an unreasonably high humidity level. It can also come from outdoors through a leaky foundation, slab or roof. High indoor humidity levels are most common in newer, efficient, airtight houses.

Since you mentioned your house is old, the source of the dampness is probably from outdoors. When a house is built over several different types of foundations, as yours is, it likely consists of several additions built at different times. There often can be leaks where the various additions were attached to one another.

Just to be certain the dampness problem is not caused from internal factors, check for any water leaks around the toilets. A common leak is where the tank mounts to the bowl. If the toilet feels loose on the floor, the wax ring at the base may be deformed and leaking. Both of these items are easy to repair yourself.

Also, try being more diligent about running kitchen and bathroom vent fans when those rooms are being used.

Run them even a little longer than you feel necessary for a while to determine if this helps relieve the moldy odor.

If the odor is still there, the moisture source is from outdoors. A crawl space floor, especially a dirt floor without proper drainage, is a common source. The concrete floor and slab can allow moisture to pass through them. Even though concrete feels hard, it is a porous material.

Make sure the crawl space floor is covered with plastic film to block moisture from coming up from the ground. A 0.006-inch thick plain polyethylene film is inexpensive and commonly used for this application. Run the film all the way up the crawl space walls and staple it to the band joist.

A better film to use is made from cross-laminated polyethylene. Several layers of film are bonded together to make it much stronger and more airtight. Plain polyethylene can have some tiny pinholes in it. Expect to pay about three to four times more for the cross-laminated material, but it probably is a wise investment.

Tape a 1-foot square piece of plastic film over the concrete basement and slab floors. Seal it well all around its perimeter. After one day, remove the film. If moisture is coming up from the basement or the slab, you will see it on the underside of the film.

If you can remove any carpeting from the concrete basement or slab floors, put a layer of plastic film down under the carpeting. Another option is to apply a liquid sealer over the floor. Water-based ones are the easiest to apply. Sources for it include: Euclid Chemical, (800) 218-2667; and L&M Construction Chemicals, (402) 453-6600.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com. To find out more about Pat Logan and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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