What Spalling Is, and How to Identify It
Excessive spalling can cause a structure to crumble
Spalling—sometimes incorrectly called "spaulding" or "spalding"—is the result of water entering brick, concrete, or natural stone. It forces the surface to peel, pop out, or flake off. It's also known as flaking, especially in limestone.
Spalling happens in concrete because of moisture in the concrete. Moisture—and often salt, too—push outward from the inside in basements especially. Spalling can eventually cause crumbling and destruction of a structure.
What Causes Spalling?
Spalling usually occurs for one of three reasons, or sometimes a combination of these reasons. Salt, particularly the sodium chloride that's used on frozen roads in many northern states, can result in oxidation or rusting of reinforcing steel when it's repeatedly introduced to a surface or building.
But spalling is more likely to occur due to the curing process or the way the concrete hardened. Carbon dioxide in the air and alkalis in the concrete mix can also interact and force cracking that admits water.
Spalling in Concrete
It's generally rare to attribute spalling in concrete to the specific materials a contractor used, although excess water can be a culprit. Knowing how concrete is made can help clear up some misconceptions.
People sometimes use the words "cement" and "concrete" interchangeably, but the acceptable term for the finished product is concrete.
Concrete consists of three basic ingredients:
- Aggregate—which can be either rock or stones
Most cement is lime-based, but there are other types of binders.
Spalling that occurs in a concrete driveway or sidewalk typically happens because the weather changed during the hardening process or something else occurred to prevent the concrete from finishing its curing. Contractors might make the mistake of adding too much water, but frankly, most don't make mixing errors.
Tearing out the driveway isn't always necessary to fix spalling in concrete. Sometimes the top layer can be removed, and a new layer poured in its place.
Spalling in Foundations
Older homes are likely candidates for spalling in their basements. The foundation might be brick, and this can extract salt in areas with high salt content.
It could be difficult to secure a mortgage on a house with an older brick foundation. Always check with your lender and real estate agent to find out about prohibitions against mortgages on a home with a brick foundation.
Fixing spalling in brick foundations can involve replacing the brick or pouring a concrete retainer wall or tuckpointing. But tuckpointing itself doesn't always alleviate the cracking and breaking off of the walls. Tuckpointing only replaces the mortar between the bricks.
Efflorescence is evident in many wet basements. You can see it on the walls, and it will flake like chalk if you scrape it with a coin. This problem can be fixed by putting in perimeter drains—dig a trench, line it with rocks, drop in a drainpipe, and attach waterproofing sheets of plastic to the walls.
Home sellers sometimes try to mask the evidence of a wet basement by painting the concrete walls with a water-repellent sealer. This attempt to conceal problems is one of several very good reasons to always obtain a professional home inspection before buying a home. A home inspector might uncover evidence of a wet basement that isn't always evident to the casual observer.
On the other hand, it doesn't necessarily mean that the foundation is spalling just because water might be present in a basement. Some homeowners may install and use sump pumps to reduce water levels in the basement and to pump out excess water during a rainstorm. Check with your home inspector for more details on how to use a sump pump.