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The Real Problem with White Staining on the Chimney

White Staining on ChimneyThe white staining that sometimes develops on chimneys is called “efflorescence.” The staining looks bad, though it can usually be cleaned off easily. The real problem with efflorescence is that it is a clear indication that moisture has worked its way into the chimney system. Moisture causes more damage to chimneys than anything else and can cause the structure to deteriorate prematurely. It’s important to have your chimney inspected by a certified professional, who can help you determine the best way to deal with the cause of the white staining on your chimney.

What is Efflorescence?

In French, efflorescence means “to flower out,” which is a good description of the staining that develops on masonry in both natural and manmade environments. When soluble solutions move through masonry and evaporate on the other side, salt residue is left behind. The residue is a crystallized or powdery substance that, over time, can look fluffy or fuzzy on the exterior of stone, brick, or block masonry.

Usually white in color, efflorescence is sometimes brown, green, or yellow. What determines the color of the staining is the type of salt that exists in the masonry. There are approximately 20 different compounds which contain crystalline deposits and can exist in masonry. Sulfates of magnesium, potassium, sodium, and calcium are common sources of the salts which produce staining on masonry. Minerals determine the color of efflorescence. For example, minerals which contain magnesium, vanadium, or molybdenum typically create greenish stains.

In What Circumstances does Efflorescence Develop?

There are certain conditions which must exist in a masonry structure for efflorescence to develop, such as:

  • There must be soluble salts contained within the masonry structure.
  • Moisture must enter the masonry to the extent that a soluble solution is created from the salts.
  • The salt must have a means to travel through the masonry and ultimately evaporate on the exterior – evaporation results in the formation of efflorescence.

What Problems can Efflorescence be an Indication Of?

The ultimate problem is the presence of moisture within the masonry. In addition to causing efflorescence, moisture can cause mold and wood rot in the attic. Flooring can be damaged by moisture in the chimney system, including carpeting and the padding and insulation underneath. The moisture also damages the chimney structure, causing the masonry to flake off and break. If moisture gets into the flue and mixes with creosote deposits, the liner can prematurely deteriorate and create the strong potential for a house fire.

bad chimney crown

Bad chimney crowns can be the cause of white staining on your chimney.

How does Moisture get into the Masonry?

There are many different means by which moisture enters a chimney system, including the following:

  • A chimney cap has not been installed at the top of the flue.
  • The lifetime of the mortar has expired and needs to be replaced.
  • The mortar is deteriorating because of the force of rainwater pouring against the chimney, particularly on steep chimneys.
  • The chimney crown is damaged, allowing moisture into the chimney system.

Tips for Preventing Efflorescence

Measures to keep moisture out of the chimney are also effective for preventing the formation of efflorescence. If all parts of the chimney are in good condition, having the chimney sealed will help to keep moisture out. Annual chimney inspections can keep the chimney well maintained. Our chimney professionals can help you with whatever is needed to prevent efflorescence from occurring or to address whatever problem has already caused white staining on your chimney.

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