HORIZONTAL FOUNDATION CRACKS
Whereas vertical cracks are to be expected in a poured concrete foundation, horizontal cracks are very different in nature, in more ways than just their direction. Vertical cracks are caused by house settlement and do not affect the structural integrity of the basement wall. Horizontal cracks, on the other hand, are caused by lateral pressure being exerted against the wall from outside. Horizontal cracks will typically run most of the length of the wall and may have several diagonal or vertical cracks branching off it. While these cracks may seem minor at first, without reinforcement they may widen over time and deflection may become evident. If one places a metal stick against the wall and it is flush with the wall below the crack, but not above it, we call this deflection. Deflection is a sure sign of compromised structural integrity. Left alone long enough, catastrophe may ensue.
Causes of horizontal foundation cracking
1/ Negative grade/Ice deposit. The negative grade around the house can cause numerous problems. Landscaping around the house should be graded so that it slopes down *away* from the foundation. If the ground is sloped down *toward* the foundation, we call this a negative grade. A sudden thaw in winter will cause snow around the house to melt and run toward the house, saturating the ground. Now imagine a sudden drop in temperature. All that water that has accumulated around the house is now frozen, forming a potentially huge ice deposit. This can exert extreme pressure against the foundation, causing horizontal cracking and a loss of structural integrity.
2/ Concrete patio, steps, driveway, or other heavy structure bolted into the foundation wall. This is unfortunately a fairly common practice. One’s foundation is meant to support the structure of the house directly over top of it, not hanging off the side. A patio or driveway is going to settle or sink over time, pulling the bolts from the foundation with it, along with actual pieces of the foundation. This sort of lateral strain against the foundation may cause horizontal cracking and loss of structural integrity.
As we can see from the above, horizontal cracking can be prevented before it even starts. One should check the condition of one’s grading every Spring. Positive grading needs to be maintained. In cases where a driveway, patio, or sidewalk has been bolted to the foundation wall, steps must sometimes be taken to ensure it maintains its positive grade as well. Mudjacking or foam lifting may be required. Do not ever let a cavity develop beneath concrete steps. Steps need to be well supported beneath to avoid the sort of structural horizontal cracking we’re talking about.
If it’s too late to take preventative steps and a horizontal crack has already been formed, reinforcement performed by a qualified contractor will be necessary to prevent the matter from becoming worse and potentially catastrophic.