Monday, April 16, 2007

Efflorescence and Stonewalls

I spoke with a fieldstone consumer today and she had a question regarding white staining that appeared on her newly constructed stonewall. The stonewall was professionally installed over this past winter. The project started in November and was completed in March. It is a 350’ wall that is 6’ high and exposed on both sides. I call this a double-faced wall.



As you can see from the picture there are white stains that are leaching onto the face of the wall. The homeowner is concerned that there may be a problem with the workmanship or quality of the stonewall. She told me that there are many similar stonewalls in her neighborhood, and none of them have the white staining that is found on hers.

Here is the answer to this situation.

When cement is used in construction it is applied wet. This means that the Portland cement, and sand are combined with water to create a workable bonding agent that will hold the stones together. As the cement dries it hardens into a stone like texture. During the drying process the water that is in the cement makes its way to the surface and evaporates once it reaches the surface. If rain or another source of water interferes with this process, the cement will retain the water longer. This allows the water to absorb more of the minerals that are in the stone and cement. Eventually the water will make its way to the surface and evaporate. If it has a high consistency of soluble salts in it the water will leave a white powdery or crystallized residue on the surface of the stone. This white stain is called efflorescence.

With the very wet weather that we have had in March and April, the cement has taken a long time to dry. Therefore, any soluble salts and minerals in the cement and stone have found their way to the surface of the stonewall.

Can this efflorescence be removed and will it come back again?

Yes it can be removed. In this situation the chances are very good that a good cleaning with water should remove the salt residue on the stone. If the salt in the stonewall is minimal then the chances of it reoccurring are slight. If the stonewall is exposed to considerable moisture it may draw out more salt, but each time should be less than the previous. As the cement dries or cures it becomes less of a conduit for allowing water to travel through. Eventually even if there are minerals trapped in the cement and stone, any water applied to the surface of the wall will evaporate before it has the chance to absorb into the stonewall and draw out any minerals.

There are many great products on the market that eliminate efflorescence stains. Try searching the word efflorescence on the internet to find some of them. I do not sell any of these products or endorse any of them.

If you have any questions regarding this topic please feel free to e-mail me your questions at sales@stoneyard.com, and I will answer them to the best of my ability.

2 comments:

Anonymous said...

Thanks for this post. I have seen that effect before and wondered what it was. Great explanation. Keep up the excellent posts!

Anonymous said...

Very clear explanation. Thanks!