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Question - Our house is about 8 years old, with a used brick fascia. About two years ago an irregular circlelike area about 3 to 4 feet in diameter started to become whitish. There is nothing on the interior wall behind the area that is any different from the surrounding, nonaffected area.

I have tried scrubbing with various solutions. Have you any thoughts on what might cause this and how can I get rid of it? - J.M., Germantown, Tenn.

Answer - The circle is caused by moisture migration through the brick to the outside surface. As the moisture reaches the surface and evaporates, there is a residue left behind called efflorescence.

This salty residue comes from the minerals in the brick and mortar. Under normal conditions the salts can be brushed off as they form.

I would suspect that the reason you are unable to remove the stain is that there is a continuous moisture source behind the brick. There is a 1/2-inch to 1-inch cavity between the back side of the brick and the exterior side of the home's walls. Moisture from under the home or from a plumbing leak can migrate to the cavity, especially if there is a foundation vent nearby.

On the interior of the home a cutout for a receptacle or switch plate also can allow for moisture migration. A cold spot on the interior wall where insulation was omitted can cause moisture to migrate to that spot.

In any case, you will have to locate the source of the problem and dry out the wall. After the moisture source is stopped, the stain can be cleaned and should disappear.