Poets, lyricists, and other writers love the metaphor of the crack in the foundation, something that is small but the forerunner of pathological damage. A crack in your foundation is information—it is telling you something, and you must invest the time to figure it out. It may turn out to not be a big problem, but it demands assessment. It’s usually best to call in a specialist to make this assessment. If you’re hesitant that they will try to sell you a suite of services and repairs, remember you can always get a free estimate or just say “no,” but that one thing is for certain—a crack, once present, will not go away and requires intervention.
It’s usually best to call in a foundation specialist to make this assessment as a foundation crack can be totally normal, or can be an indicator of something serious. If you’re hesitant that they will try to sell you a suite of services and repairs, remember you can always get a free estimate or just say “no,” but that one thing is for certain—a crack, once present, will not go away and may indicate a more serious problem with your foundation.
Here in Toronto, foundation cracks are quite common. Many foundation cracks are simple from shifting foundations and aging homes “settling” over time. While others are from shoddy construction from the start or an environment surrounding your foundation that is contributing to its erosion. As you can see, sometimes it’s nothing but other times it can be serious.
Even if the foundation crack is not serious, it can still cause water issues and can lead to foundation erosion over time if water is allowed to continuously channel through your foundation into your basement.
So, let’s take a look at some of the most common information—the most common causes—of basement foundation cracks.
Concrete is a mixture of cement, water, and aggregate. It is poured and then dries and cures. Early in the curing stage, the concrete enters its plastic state. In this state, it is still very moist, but it continues to lose moisture during the curing process. Steve VandeWater, in his paper “Why Concrete Cracks,” illuminates, “because concrete is a very rigid material, this shrinking creates stress on the concrete slab. As the concrete shrinks, it drags across its granular subgrade. This impediment to its free movement creates stress that can literally pull the slab apart.” He continues, “when the stress becomes too great for the now hardened concrete, the slab will crack in order to relieve tension.”
VandeWater points out that these plastic-state cracks are almost sure to occur near obstacles, objects placed in the concrete slab, such as drains, plumbing fixtures, etc. The concrete has no ability to shrink around these objects.
Contraction cracks not a disaster
Fortunately, though some cracks due to the contraction of concrete during its curing process are inevitable, they aren’t likely to cause serious structural damage. They’re mostly a nuisance, providing a gateway for things like water leaking or insects.
A second big reason for basement cracks is your house settling into the soil. Daniel Friedman is a construction worker who discusses this issue. He says that floor slabs need to be poured into “compacted fill” as opposed to “soft fill.” To explain what this means, he clearly illustrates, “my first job in construction was raking a huge dirt pile out to ‘level’ inside of an already poured and built footing and masonry block foundation wall. Once the dirt was roughly ‘level’ via my hand rake, the builder went ahead and poured his floor slab. ‘Compacted fill’ was not in our vocabulary.”
Floor slabs not poured in this manner are more vulnerable to settling into the soil, and in the vocabulary of the business, “floating,” moving as the soil moves.
Yet, it’s just as often that the culprit is not construction workers at all. Mother Nature will damage your foundation if you give her half a chance. Too much rain will cause the rising groundwater to squeeze the house’s foundation. The bad news is that dry periods are problematic, too, since dry soil shrinks, in turn causing you foundation to settle.
In Winter, groundwater freezing also causes pressure on your foundation, pressure that may lead to cracking.
One thing to do to attempt to combat the sorts of pressure described above is to improve the tensile strength of your concrete. Tensile strength is the ability to withstand force that could pull something apart. Strange though it might seem, concrete actually has fairly low tensile strength. Improving it can be a matter of a contractor adding rebar of fiber to the concrete.
If the cracks you observe are horizontal, you should take them that much more seriously, since they are indications of serious structural problems. Consultant Gary Fuller explains, “if the foundation does not provide enough lateral support, the walls will deflect inward and create horizontal cracking.”
Mike Holmes, host of the TV show “Holmes Inspection,” alerts us that horizontal cracking higher on the walls calls from water or frost, as “water from your downspouts or sump pump saturates the area, it freezes and exerts pressure on the basement wall.”
While there may not be one cure for basement cracks or one correct course of action, just be sure not to ignore the problem. Take a lesson from the poets and don’t let the cracks spread and leave you on a foundation of rubble.
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If you live in Toronto or the surrounding GTA, we offer a free in-home inspection and estimate for foundation cracks, basement waterproofing and related basement renovation projects. You can contact us here.