The interesting fact about foundation cracks is that when they are discovered, they tend to scare homeowners. There is not a lot of education or awareness about foundation cracks and most owners who are afraid of getting ‘bad news’ in the form of a large contracting bill, will attempt to mask the crack themselves or ignore it. Unfortunately the ‘out of sight out of mind’ mentality does not do much to fix the problem, and can lead to more serious and costly problems down the road.
We receive questions and inquiries about foundation cracks on a weekly basis, and the prognosis for your basement can only be determined after we have investigated the location of the cracks and other factors, including an assessment for moisture and other contributing problems. Let’s take a look at facts; why they happen, and what can be done to repair foundation cracks.
Understanding the Strength of Concrete
Take a quick look around you. Everything from the road beneath your vehicle, to the cementing of street signs and poles to bricks, break walls, stairs and more are constructed from the manmade material we know as concrete. It is by far the most prevalent building material because of its flexibility; it can be poured or formed into anything required for residential or commercial engineering.
Concrete is made of Portland cement (basic ingredient) which creates a paste with water, sand and powdered rock. A bricklayer in England (Joseph Aspdin) was credited for inventing Portland cement in the early 19th century with a composite of limestone and clay, which he made in his own kitchen. Today cement is made from a controlled combination of calcium, silicon, aluminum and other metal fibers including iron. Different types of cement may include limestone, organic shells, shale, slate dust and other silica based materials that are superheated to a solid rock like material, and then ground up for use in construction.
Taking some of the strongest mineral fibers in the world creates quality cement that can safely be used as a foundation for a residential single or multiple story home, or even large structures such as high rise commercial buildings.
Fun Fact: One of the tallest new international structures in the world the “Burj Dubai” stands at 2,717 feet tall and required 330,000 cubic meters of concrete to complete.
How Does Damage to Concrete Occur?
We understand that concrete is engineered to be a strong and chemically reliable building material, and builders place a lot of trust in the composite. However for all its strength and durability, concrete is a natural material that is subject to structural weakness when it is impacted by other natural forces. When concrete is placed under duress through pressure or the environment, fissures or cracks occur.
Concrete forms natural pores when it is setting and during construction. When concrete is exposed to water, the pores collect moisture. Engineers consider 91% water saturation to be a critical structural risk to untreated concrete. At that time freezing and thawing will create stress on concrete, which results in structural cracks and loss of surface integrity seasonally in the freeze-thaw cycle. This can be further accelerated by salt in the water, which increases corrosion.
It is important to note that most residential zoned soil composites contain up to 45% moisture. In essence, your concrete foundation is a barrier between your home and a large amount of natural water on a daily basis. This is why preventative maintenance of your home’s foundation is so important to protect the integrity of your masonry before problems occur.
While concrete is a reliable and strong building material, it is subject to stressors such as weight and load bearing. This is why you will find cracks and indications of pressure damage around load bearing walls, poles and heavy structures that have been secured by concrete at the top or base of the item. This is referred to as pressure damage.
Sulfates have a negative impact on the integrity of concrete and can come from a variety of sources including sea water, oxidation of sulfide in natural clay sediment and even anaerobic bacteria from sewers that produce caustic sulfur dioxide. The internal composition of masonry (which contains some sulfates) can amplify over time and attack and weaken mortar.
Categories of Concrete Cracks: How Serious Is It?
According to the U.S. General Services Administration, there are a variety of classification of cracks in concrete that differ according to severity and activity. A crack can be diagnosed as dormant, or unmoving which poses less of a threat for structures than an active crack, which continues to expand both in width and travel across hard structure surfaces, compromising the integrity of foundations.
Whether dormant or active, all foundation cracks present safety risks as they allow water and salt to permeate into the masonry accelerating erosion. In the case of a residential home, cracks can also lead to infestation of vermin including mice and insects.
Cracks are defined or diagnosed by visual inspection of the direction of travel, the overall width of the crack and the depth of the fissure. The below information is provided as a reference and is not intended to replace the expert advice and assessment of an engineering professional.
|Type of Structural Crack||Visual Inspection|
|Pattern Cracks||A regular pattern of very fine openings. Can be caused by poor quality concrete or inconsistent application (thickness) of concrete.|
|Hairline Cracks||Randomly located very fine cracks. They can be a single crack or multiple hairline cracks over the surface space, but not in a pattern.|
|D-Cracks||Fine cracks that appear at very close proximity to each other.|
|Shrinkage Cracks||Parallel to the floor, these cracks appear in concrete which is setting but not yet hardened. They appear as straight lines visually. Diagonal lines are referred to as ‘Plastic Cracking’ at the top of a slab of concrete such as a floor.|
|Settlement Cracks||Occurs around the base of a pole, support beam or brick wall that has been secured with concrete. Cracks appear naturally as the weight settles into the concrete foundation.|
|Structural Cracks||This happens as a result of corrosion in older buildings or where concrete has been exposed to stresses such excessive weight over time.|
|Tension Cracks||Where concrete has been reinforced with iron or metal infrastructure for additional strength. Tension zones can express as patterns in the surface of the concrete.|
|Thermal Induced Cracks||Temperature induced stress cracks from excessive heat or cold.|
Foundation and engineering experts are often concerned when homeowners choose to attempt diagnostic and repair of foundation cracks. Without the training and expertise to source the cause of the cracks or stress on your concrete and foundation, it can be difficult to choose the right repair method. Ignoring cracks in your basement or foundation is easy, but coping with the added expense of a more serious problem down the road is not.
Rather than guess at the cost of the repair or severity of the damage, it’s best to consult with a professional who can thoroughly evaluate the situation and give you an accurate plan of action and quote on pricing. Sometimes a crack in the concrete is just a small crack, and sometimes it is indicative of a much more serious problem that requires immediate attention. Consult with a trusted engineering professional to get an accurate evaluation.