How to clean away cellar efflorescence

We have a problem with the powdery crust -- efflorescence -- that forms on the inside of our concrete-block basement wall. Sometimes there even is a the chipping away of the masonry surface. the outside of the wall below grade was waterproofed with asphaltum and asphalt paper, supported by footing drains. The interior walls were sealed with, presumably, water- resistant paint.

This efflorescence is so bad that when it is removed with a brush, chips of the concrete block flake off as well. Does this mean that the entire wall is disintegrating? Do we need to redo anything outside the wall below grade, or can we simply apply something to the inside wall? Margaret van B. Landry Berkeley, Calif.

I'd not be too concerned about the structural integrity of the masonry, nor would I redo anything outside below grade without first calling on a professional for an inspection and recommendation.

You can rid the interior masonry of its efflorescence by scrubbing it with an acid cleaner which is available from a builder-supply house.

Follow the labeled directions explicitly, especially concerning the safety measures you should take when handling an acid. Clean Etch, made by Sealwall of Eastlake, Ohio, is one such product.

Rinse the wall with voluminous amounts of clean water.

If the wall is chipped to a great degree, patch it with an acrylic cement which is designed for vertical surfaces and is equal to Sealwall's Patchit.

Then apply a sure-fire permanent water- proofing agent, such as Sealwall, or equal. If you follow the directions thoroughly, you should have no further efflorescence problems.

Efflorescence is a surface problem alone and should have no deleterious effect on the concrete mass.

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