It is a problem? Well it can be. Is it serious? Well it can be but not usually. Can I fix the cause of this problem? Yes you can but first let’s try to define what this substance is and then offer some solutions on how to prevent its’ occurrence.
Problem - Efflorescence is a white power that when visible on the surface of brick, block or stone masonry is an indication of excessive water within the masonry structure.
It often occurs when the flashing, cap stones, rowlocks, chimney crowns, etc. leak allowing rain water to enter the masonry wall system. Once the water is inside the wall it will dissolve soluble salts within the individual masonry units and the mortar.As the water migrates to the outside surface of the masonry wall by ‘wicking’ action it carries these soluble salts with it and then deposits them on the surface of the masonry during evaporation. This is a sure sign of excessive water infiltration into the masonry and if not taken care of, can lead to costly damage with premature deterioration.
Solution: As with any water problem you must stop the water from entering the wall system at the source. Flashing joints must be checked periodically as well as mortar joints on cap stones and rowlocks and cracks repaired on chimney crowns. Once the leak has been repaired, wait for a few weeks of high pressure weather to arrive which will dry out the wall system.
Many times rain or a simple hosing will wash the efflorescence off, if it is minor. Usually though, further steps are needed to remove the stain completely. You may remove the efflorescence by using a stiff brush to scrub the masonry surface while applying a neutralizer. Your neutralizer should consist of 1 cup of household bleach mixed with five gallons of cold water. Several applications may be necessary. Make sure to flush the surface well when you are finished applying the neutralizer.
If your effort was not effective then there may be other issues that need to be addressed by a professional masonry repair expert. Contact your local repair expert, explain the steps you have taken and ask for advice on what should be done next.