Q-Six months ago a masonry contractor constructed a brick retaining wall in my garden. Two months after he finished, white deposits began to appear in many locations on the face of the brick. The contractor has tried to wash them off with acid but the stains continue to reappear. I think the brick is defective. What, if anything, can be done?
A-You appear to be a victim of efflorescence, a common problem with masonry walls. It is a deposit of a soluble salt that was present in the bricks, mortar or the backfill material behind the wall. I don’t believe that your bricks are defective.
Efflorescence is, for the most part, a visual problem. Very rarely does it cause structural problems. Though it is not a simple problem to correct, efflorescence often diminishes with time.
The condition can occur on concrete as well as brick or masonry surfaces. Several conditions must coexist before efflorescence will appear. The soluble salts must be present in the bricks or mortar, or be transported by water into the masonry from another source. There must be sufficient water to carry the salts to the surface of the masonry. And, finally, evaporation must take place. This evaporation causes the salts to come out of solution and be left behind as the deposits you see.
The soluble salts that cause the problem can come from many chemical elements or minerals, many of which can be found in the materials from which bricks are made. Also, the sand that is used in the mortar can have significant quantities of soluble salts. For this reason, it is always best to used washed sand from a high quality sand and gravel pit. The soluble salts can also be present in the soil behind your wall or the water that was used to mix the mortar.
Efflorescence will stop on its own if the supply of soluble salt material in the bricks or mortar becomes exhausted. It also can stop if the source of water that dissolves the soluble salts is cut off. The process also can stop if the water in which the salts are dissolved is prevented from getting to the surface of the masonry.
Because your wall is located in a garden, the supply of water that dissolves the salts and carries them to the surface of the wall will probably be sufficient for a long period of time. If the back or top of the wall was not treated with a compound that prevents water penetration, you will have to wait for the supply of salt material to diminish. I have seen cases where it takes several years for the deposits to totally disappear.
Depending upon the soluble salt or salts that are causing the problem, you have several options. You can sometimes remove the dried deposits with a stiff brush. Sometimes water will wash the salts from the wall. However, this process can sometimes dissolve the salts and cause them to soak back into the wall. You may have to use a very weak solution of muriatic acid. Only attempt this method if you know for a fact that the acid will work effectively on the type of salt present.
Acid solutions can cause severe burns to skin and eyes. If you attempt to try this yourself, be certain to wear complete protective gear. Carefully follow the directions on the acid container. Acid washes improperly applied can damage the masonry surface as well. They should only be performed with utmost caution.
———-
Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a list of publications describing efflorescence, its causes, prevention and elimination, please send $1.50 and a business-size, stamped, self-addressed envelope to Tim Carter at the above address. Ask for Builder Bulletin No. 214.
You can obtain a free order form for a wide variety of individual job bid sheets by sending a business-size SASE to the same address.
