Wednesday, February 4, 2004

White powder on new masonry can make you nuts

Tribune Media Services

Q. I feel our new home has some serious problems, but our builder disagrees. The house is less than 6 months old, but we have ugly white deposits that are leaching out of our chimney, a wing wall that juts from a corner of our home and a retaining wall. I feel there must be something wrong for this to happen. The more I scrub, the worse the problem gets. What is wrong, and what can be done to fix the problem? — Andrew M., Loveland, Ohio.

A. Don’t put the noose around the builder’s neck just yet. The white deposits you are seeing are probably not his fault, although there might have been some things he could have done during construction to minimize the presence of the powder.

The first thing to realize is that these mineral deposits are just an aesthetic problem. They do not compromise the structural integrity of any of the masonry in and about your new home, but chronic water that gets into masonry can cause problems over time.

The white powder you see is efflorescence. The brick, stone, concrete block, mortar etc. contain water soluble salts that are the source of the white deposits. Soil behind retaining walls can also contain these same salts.

These trapped salts are set into motion when water enters masonry. The water dissolves the salts and carries them through the masonry toward the surface. Sunlight and wind draw the water to the surface, but as the water evaporates the salts are left behind.

The salts contained in the brick, mortar, stone and concrete block eventually exhaust themselves, and the white mineral deposits simply go away. But salts within soil can persist for decades.

Each time you try to wash the chimney and wall surfaces to remove the salts, you actually compound the problem. The water you use simply soaks into the masonry surfaces and dissolves the salts to create more problems days later. The surfaces typically look fantastic when wet, but the white powder appears again when the surfaces dry.

To stop the efflorescence now, you must stop all water from entering the masonry surfaces. This is somewhat easy to do at the chimney and any exterior masonry walls, but far more difficult to do with the retaining wall. If you stop the water, there is no transport medium to carry the soluble salts to the surface where you will see them.

The chimney and wing wall can be treated with a silane/siloxane water repellent. They can also be coated with a new clear masonry sealer that bridges cracks up to 1/8 inch. Using these products in tandem virtually assures that you will stop water from getting into the masonry.

The retaining wall that is backfilled with dirt should have been treated with a waterproofing compound that would have stopped water infiltration into the wall. That is very hard to do now as the fill behind the wall will have to be removed and the wall cleaned and allowed to dry before the back side of the wall can be waterproofed. The builder should have done this when the wall was being constructed. It would have taken minutes instead of the days it will now take to stop the efflorescence.

I would not try to do any remedial work until the weather moderates. You want days where the temperature rises to 65 F or above to get excellent results from the sealants and water repellents. Be sure to inspect the chimney crown for cracks that might allow water to enter the chimney’s masonry core. If you discover cracks, you need a different elastomeric coating for the chimney crown.

I think you should have a discussion with your builder to see if he will help you out with the retaining wall fix. Perhaps he can excavate the fill and clean the wall and leave you to apply the waterproofing compound. The builder can then backfill since he has access to equipment that can do it rapidly and easily.

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