Spalling is the deterioration of concrete by crumbling or flaking. The main cause of spalling is water. When brick is exposed to water consistently, some of the water is absorbed through the porous material of the brick. When this water freezes and thaws repeatedly, it causes the brick to fall apart.
Other sources of spalling are high pressure washing, water hitting the wall directly by driving rains, water from downspouts, gutters and roofs and water seeping up from the soil. Vapor air escaping through the wall from inside the building, chemical cleaning and non-breathable brick sealers are additional causes.
Most Common Cause
The most severe spalling is the damage from freezing and thawing. Rain or snow is absorbed by the concrete and because of the expansion of water molecules upon freezing, this expansion and contraction does considerable damage.
The amount of damage is dependent on the amount of water, the absorption ability of the brick, and the number of freeze/thaw cycles. Some brick is not evenly porous. It has a softer more absorptive center. This brick can deteriorate very rapidly. Especially when the outer, harder brick is worn away or moisture has managed to seep into it’s softer center.
At The Grade
Using the wrong brick at or below grade can lead to increased spalling. If all the brick at or below grade is spalling but the brick above grade is not, chances are that this brick was not intended for use below grade.
Another cause of spalling is high pressure washing. Whether with water or sand, this type of abrasive cleaning will deteriorate the mortar and possibly the brick.
High impact damage is another cause of spalling. If the concrete has suffered an impact that has removed some of the surface, this area will be more prone to moisture absorption.
Some sealants may protect brick from water absorption due to driving rain but many of them can also act like a rubber glove. They may protect it from initial absorption but can seal in the moisture that does get through, resulting in more damage. A breathable sealant will help. This still should be used with caution.
Water Is The Enemy
Water is concrete’s worst enemy. An important part of maintaining a brick wall is to keep the mortar intact. Bricks with missing, loose or crumbling mortar are much more susceptible to moisture. Regular upkeep on a brick wall includes repointing the joints and reapplying new mortar on a regular basis.
If the brick wall is part of the main structure of the building, the weakening of mortar can prove to be a severe problem. The integrity of the wall is at stake. This can be not only expensive to repair or replace but it can also prove to be a safety hazard.
Examine The Damage
Further examination of the extent of the deterioration is necessary here. Pay special attention to areas where the brick is exposed to sources of water. Downspouts, gutters, below windows and behind shrubs. Look anywhere that the accumulation of water meets the brick. It may be difficult to predict whether or not the deterioration will continue. A comparison of the wall to an adjoining area can be helpful.
In cases where the wall is part of the structure, rebuilding may be necessary. Adding stucco or siding to the brick may help support the wall. This can prolong the need to rebuild the wall for some time. It may eliminate the deterioration altogether. Make sure to use a treatment that is breathable to prevent further spalling of the masonry.
Inspect the mortar work all along the wall in suspect. If it is a poor job, consider repointing the entire area. Are there pronounced ledges sticking out between the bricks? If so, these ledges can create traps that retain and hold moisture against the wall.
Watch for which direction the rain is driven up against the wall. When the strength of a structural wall is in question it is very important to keep the area under observation. If the wall is a veneer, it is more of a question of aesthetics. Stucco or siding may be the only solution you really need.