Replies

1. 
   Brewskie | Jan 08, 1999 01:17am | #1

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   The white powdery substance you are reffering to is what is known as efflorescence.

   This is caused by salts (alkali) leaching to the surface after the substrates have become saturated. This breaks down the minerals in the stucco and is why some plasterers refer to it as 'cancer' because it will usually grow and there is no way to fix it without removal.

   Temperature usually does not have a direct effect for the creation of efflorescence. It is a product of the salts reaction to moisture.

   The best thing to do here would be to remove the affected areas of the stucco and re-stucco it.

   After the areas have been restuccoed then apply a good, high quality, sealer. I usually use a product known as "777" made by Thoro Systems. This product will seal the stucco yet still allow it to breathe.....(thereby allowing moisture to escape if it were to get in).

   Another way to mitigate a persistent problem with efflorescence would be to channel water away from the foundation and do what ever it takes to keep the areas dry.

   Brian Ewing

   Craftsmen Square

2. 
   Guest_ | Jan 08, 1999 01:30am | #2

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   I suspect the source of moisture is capillary leaching up from below grade. I don't think any drainage solution or sealing will work. You will need to remove the stucco below 6" above grade to stop this. For appearance you can color this with a very liquid wash of stucco color coat brushed on. This is called dash, and is commonly used to color foundations to match stucco. Remove and repair any affected areas above and then seal.

3. 
   Brewskie | Jan 08, 1999 06:50pm | #3

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   Removing the stucco won't make a difference if the ground is so wet that water will wick up through it. If you remove the stucco the water will still wick up through the block or brick substrates.

   It remains that the problem is water getting up through the ground or being puddled up against it. This would mean that you have to mitigate the water problem.

   Please tell your plasterer to "fog coat" the stucco if you have any problems with color, as a dash coat is a type of texture that may not match your original. (A dash coat is a sand type of texture. Usually machine applied though easily applied with a brush with a splash movement....in some areas it's known as a "splatter dash")

   A fog coat consists of Portland cement, lime and pigmentation. Most manufacturers sell this for their stucco products. However be carefull that you get these ingredients as some manufacturers sell a type of paint for their fog coat that is really a bad thing for stucco (you should NEVER paint your stucco). This fog coat should be sprayed on with a Hudson type sprayer.

   Brian Ewing

   Craftsmen Square

4. 
   Rich_Fatooh | Jan 08, 1999 06:52pm | #4

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   The stucco which is on the exterior of the house's foundation has been producing a white powder in various places and seems to be breaking down the stucco itself into powder. What is this and how can I solve this problem? This occurrs only in the winter and cold temperatures. The house is located in Virginia.